terraform: ugly huge change to weave in new HCL2-oriented types

Due to how deeply the configuration types go into Terraform Core, there
isn't a great way to switch out to HCL2 gradually. As a consequence, this
huge commit gets us from the old state to a _compilable_ new state, but
does not yet attempt to fix any tests and has a number of known missing
parts and bugs. We will continue to iterate on this in forthcoming
commits, heading back towards passing tests and making Terraform
fully-functional again.

The three main goals here are:
- Use the configuration models from the "configs" package instead of the
  older models in the "config" package, which is now deprecated and
  preserved only to help us write our migration tool.
- Do expression inspection and evaluation using the functionality of the
  new "lang" package, instead of the Interpolator type and related
  functionality in the main "terraform" package.
- Represent addresses of various objects using types in the addrs package,
  rather than hand-constructed strings. This is not critical to support
  the above, but was a big help during the implementation of these other
  points since it made it much more explicit what kind of address is
  expected in each context.

Since our new packages are built to accommodate some future planned
features that are not yet implemented (e.g. the "for_each" argument on
resources, "count"/"for_each" on modules), and since there's still a fair
amount of functionality still using old-style APIs, there is a moderate
amount of shimming here to connect new assumptions with old, hopefully in
a way that makes it easier to find and eliminate these shims later.

I apologize in advance to the person who inevitably just found this huge
commit while spelunking through the commit history.

backend/backend.go

@@ -9,12 +9,12 @@ import (
 	"errors"
 	"time"
 
-	"github.com/hashicorp/terraform/configs"
-
 	"github.com/zclconf/go-cty/cty"
 
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/command/clistate"
 	"github.com/hashicorp/terraform/config/configschema"
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/configs/configload"
 	"github.com/hashicorp/terraform/state"
 	"github.com/hashicorp/terraform/terraform"
@@ -184,11 +184,10 @@ type Operation struct {
 	// behavior of the operation.
 	AutoApprove  bool
 	Destroy      bool
+	Targets      []addrs.Targetable
+	Variables    map[string]UnparsedVariableValue
+	AutoApprove  bool
 	DestroyForce bool
-	ModuleDepth  int
-	Parallelism  int
-	Targets      []string
-	Variables    map[string]interface{}
 
 	// Input/output/control options.
 	UIIn  terraform.UIInput

backend/local/backend_apply.go

@@ -137,11 +137,11 @@ func (b *Local) opApply(
 
 	// Start the apply in a goroutine so that we can be interrupted.
 	var applyState *terraform.State
-	var applyErr error
+	var applyDiags tfdiags.Diagnostics
 	doneCh := make(chan struct{})
 	go func() {
 		defer close(doneCh)
-		_, applyErr = tfCtx.Apply()
+		_, applyDiags = tfCtx.Apply()
 		// we always want the state, even if apply failed
 		applyState = tfCtx.State()
 	}()
@@ -165,12 +165,8 @@ func (b *Local) opApply(
 		return
 	}
 
-	if applyErr != nil {
-		diags = diags.Append(tfdiags.Sourceless(
-			tfdiags.Error,
-			applyErr.Error(),
-			"Terraform does not automatically rollback in the face of errors. Instead, your Terraform state file has been partially updated with any resources that successfully completed. Please address the error above and apply again to incrementally change your infrastructure.",
-		))
+	diags = diags.Append(applyDiags)
+	if applyDiags.HasErrors() {
 		b.ReportResult(runningOp, diags)
 		return
 	}

backend/local/backend_local.go

@@ -2,7 +2,6 @@ package local
 
 import (
 	"context"
-	"errors"
 
 	"github.com/hashicorp/errwrap"
 
@@ -58,15 +57,23 @@ func (b *Local) context(op *backend.Operation) (*terraform.Context, state.State,
 	opts.Destroy = op.Destroy
 	opts.Targets = op.Targets
 	opts.UIInput = op.UIIn
-	if op.Variables != nil {
-		opts.Variables = op.Variables
-	}
 
-	// FIXME: Configuration is temporarily stubbed out here to artificially
-	// create a stopping point in our work to switch to the new config loader.
-	// This means no backend-provided Terraform operations will actually work.
-	// This will be addressed in a subsequent commit.
-	opts.Module = nil
+	// Load the configuration using the caller-provided configuration loader.
+	config, configDiags := op.ConfigLoader.LoadConfig(op.ConfigDir)
+	diags = diags.Append(configDiags)
+	if configDiags.HasErrors() {
+		return nil, nil, diags
+	}
+	opts.Config = config
+
+	variables, varDiags := backend.ParseVariableValues(op.Variables, config.Module.Variables)
+	diags = diags.Append(varDiags)
+	if diags.HasErrors() {
+		return nil, nil, diags
+	}
+	if op.Variables != nil {
+		opts.Variables = variables
+	}
 
 	// Load our state
 	// By the time we get here, the backend creation code in "command" took
@@ -77,23 +84,14 @@ func (b *Local) context(op *backend.Operation) (*terraform.Context, state.State,
 
 	// Build the context
 	var tfCtx *terraform.Context
+	var ctxDiags tfdiags.Diagnostics
 	if op.Plan != nil {
-		tfCtx, err = op.Plan.Context(&opts)
+		tfCtx, ctxDiags = op.Plan.Context(&opts)
 	} else {
-		tfCtx, err = terraform.NewContext(&opts)
+		tfCtx, ctxDiags = terraform.NewContext(&opts)
 	}
-
-	// any errors resolving plugins returns this
-	if rpe, ok := err.(*terraform.ResourceProviderError); ok {
-		b.pluginInitRequired(rpe)
-		// we wrote the full UI error here, so return a generic error for flow
-		// control in the command.
-		diags = diags.Append(errors.New("Can't satisfy plugin requirements"))
-		return nil, nil, diags
-	}
-
-	if err != nil {
-		diags = diags.Append(err)
+	diags = diags.Append(ctxDiags)
+	if ctxDiags.HasErrors() {
 		return nil, nil, diags
 	}
 
@@ -106,8 +104,9 @@ func (b *Local) context(op *backend.Operation) (*terraform.Context, state.State,
 			mode |= terraform.InputModeVar
 			mode |= terraform.InputModeVarUnset
 
-			if err := tfCtx.Input(mode); err != nil {
-				diags = diags.Append(errwrap.Wrapf("Error asking for user input: {{err}}", err))
+			inputDiags := tfCtx.Input(mode)
+			diags = diags.Append(inputDiags)
+			if inputDiags.HasErrors() {
 				return nil, nil, diags
 			}
 		}

backend/local/backend_plan.go

@@ -87,20 +87,20 @@ func (b *Local) opPlan(
 
 	// Perform the plan in a goroutine so we can be interrupted
 	var plan *terraform.Plan
-	var planErr error
+	var planDiags tfdiags.Diagnostics
 	doneCh := make(chan struct{})
 	go func() {
 		defer close(doneCh)
 		log.Printf("[INFO] backend/local: plan calling Plan")
-		plan, planErr = tfCtx.Plan()
+		plan, planDiags = tfCtx.Plan()
 	}()
 
 	if b.opWait(doneCh, stopCtx, cancelCtx, tfCtx, opState) {
 		return
 	}
 
-	if planErr != nil {
-		diags = diags.Append(planErr)
+	diags = diags.Append(planDiags)
+	if planDiags.HasErrors() {
 		b.ReportResult(runningOp, diags)
 		return
 	}

backend/local/backend_refresh.go

@@ -60,11 +60,11 @@ func (b *Local) opRefresh(
 
 	// Perform the refresh in a goroutine so we can be interrupted
 	var newState *terraform.State
-	var refreshErr error
+	var refreshDiags tfdiags.Diagnostics
 	doneCh := make(chan struct{})
 	go func() {
 		defer close(doneCh)
-		newState, refreshErr = tfCtx.Refresh()
+		newState, refreshDiags = tfCtx.Refresh()
 		log.Printf("[INFO] backend/local: refresh calling Refresh")
 	}()
 
@@ -74,8 +74,8 @@ func (b *Local) opRefresh(
 
 	// write the resulting state to the running op
 	runningOp.State = newState
-	if refreshErr != nil {
-		diags = diags.Append(refreshErr)
+	diags = diags.Append(refreshDiags)
+	if refreshDiags.HasErrors() {
 		b.ReportResult(runningOp, diags)
 		return
 	}

backend/unparsed_value.go

@@ -0,0 +1,84 @@
+package backend
+
+import (
+	"fmt"
+
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/terraform"
+	"github.com/hashicorp/terraform/tfdiags"
+)
+
+// UnparsedVariableValue represents a variable value provided by the caller
+// whose parsing must be deferred until configuration is available.
+//
+// This exists to allow processing of variable-setting arguments (e.g. in the
+// command package) to be separated from parsing (in the backend package).
+type UnparsedVariableValue interface {
+	// ParseVariableValue information in the provided variable configuration
+	// to parse (if necessary) and return the variable value encapsulated in
+	// the receiver.
+	//
+	// If error diagnostics are returned, the resulting value may be invalid
+	// or incomplete.
+	ParseVariableValue(mode configs.VariableParsingMode) (*terraform.InputValue, tfdiags.Diagnostics)
+}
+
+func ParseVariableValues(vv map[string]UnparsedVariableValue, decls map[string]*configs.Variable) (terraform.InputValues, tfdiags.Diagnostics) {
+	var diags tfdiags.Diagnostics
+	ret := make(terraform.InputValues, len(vv))
+
+	for name, rv := range vv {
+		var mode configs.VariableParsingMode
+		config, declared := decls[name]
+		if declared {
+			mode = config.ParsingMode
+		} else {
+			mode = configs.VariableParseLiteral
+		}
+
+		val, valDiags := rv.ParseVariableValue(mode)
+		diags = diags.Append(valDiags)
+		if valDiags.HasErrors() {
+			continue
+		}
+
+		if !declared {
+			switch val.SourceType {
+			case terraform.ValueFromConfig, terraform.ValueFromFile:
+				// These source types have source ranges, so we can produce
+				// a nice error message with good context.
+				diags = diags.Append(&hcl.Diagnostic{
+					Severity: hcl.DiagError,
+					Summary:  "Value for undeclared variable",
+					Detail:   fmt.Sprintf("The root module does not declare a variable named %q. To use this value, add a \"variable\" block to the configuration.", name),
+					Subject:  val.SourceRange.ToHCL().Ptr(),
+				})
+			case terraform.ValueFromEnvVar:
+				// We allow and ignore undeclared names for environment
+				// variables, because users will often set these globally
+				// when they are used across many (but not necessarily all)
+				// configurations.
+			case terraform.ValueFromCLIArg:
+				diags = diags.Append(tfdiags.Sourceless(
+					tfdiags.Error,
+					"Value for undeclared variable",
+					fmt.Sprintf("A variable named %q was assigned on the command line, but the root module does not declare a variable of that name. To use this value, add a \"variable\" block to the configuration.", name),
+				))
+			default:
+				// For all other source types we are more vague, but other situations
+				// don't generally crop up at this layer in practice.
+				diags = diags.Append(tfdiags.Sourceless(
+					tfdiags.Error,
+					"Value for undeclared variable",
+					fmt.Sprintf("A variable named %q was assigned a value, but the root module does not declare a variable of that name. To use this value, add a \"variable\" block to the configuration.", name),
+				))
+			}
+			continue
+		}
+
+		ret[name] = val
+	}
+
+	return ret, diags
+}

command/apply.go

@@ -7,14 +7,14 @@ import (
 	"sort"
 	"strings"
 
-	"github.com/hashicorp/terraform/configs"
-
-	"github.com/hashicorp/terraform/tfdiags"
-
 	"github.com/hashicorp/go-getter"
+
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/backend"
 	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/terraform"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // ApplyCommand is a Command implementation that applies a Terraform
@@ -314,7 +314,7 @@ Options:
 	return strings.TrimSpace(helpText)
 }
 
-func outputsAsString(state *terraform.State, modPath []string, schema []*config.Output, includeHeader bool) string {
+func outputsAsString(state *terraform.State, modPath addrs.ModuleInstance, schema []*config.Output, includeHeader bool) string {
 	if state == nil {
 		return ""
 	}

command/flag_kv.go

@@ -3,6 +3,11 @@ package command
 import (
 	"fmt"
 	"strings"
+
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/hcl2/hcl/hclsyntax"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // FlagStringKV is a flag.Value implementation for parsing user variables
@@ -41,3 +46,34 @@ func (v *FlagStringSlice) Set(raw string) error {
 
 	return nil
 }
+
+// FlagTargetSlice is a flag.Value implementation for parsing target addresses
+// from the command line, such as -target=aws_instance.foo -target=aws_vpc.bar .
+type FlagTargetSlice []addrs.Targetable
+
+func (v *FlagTargetSlice) String() string {
+	return ""
+}
+
+func (v *FlagTargetSlice) Set(raw string) error {
+	// FIXME: This is not an ideal way to deal with this because it requires
+	// us to do parsing in a context where we can't nicely return errors
+	// to the user.
+
+	var diags tfdiags.Diagnostics
+	synthFilename := fmt.Sprintf("-target=%q", raw)
+	traversal, syntaxDiags := hclsyntax.ParseTraversalAbs([]byte(raw), synthFilename, hcl.Pos{Line: 1, Column: 1})
+	diags = diags.Append(syntaxDiags)
+	if syntaxDiags.HasErrors() {
+		return diags.Err()
+	}
+
+	target, targetDiags := addrs.ParseTarget(traversal)
+	diags = diags.Append(targetDiags)
+	if targetDiags.HasErrors() {
+		return diags.Err()
+	}
+
+	*v = append(*v, target.Subject)
+	return nil
+}

command/graph.go

@@ -127,12 +127,13 @@ func (c *GraphCommand) Run(args []string) int {
 
 	// Skip validation during graph generation - we want to see the graph even if
 	// it is invalid for some reason.
-	g, err := ctx.Graph(graphType, &terraform.ContextGraphOpts{
+	g, graphDiags := ctx.Graph(graphType, &terraform.ContextGraphOpts{
 		Verbose:  verbose,
 		Validate: false,
 	})
-	if err != nil {
-		c.Ui.Error(fmt.Sprintf("Error creating graph: %s", err))
+	diags = diags.Append(graphDiags)
+	if graphDiags.HasErrors() {
+		c.showDiagnostics(diags)
 		return 1
 	}
 

command/import.go

@@ -1,15 +1,19 @@
 package command
 
 import (
+	"errors"
 	"fmt"
 	"log"
 	"os"
 	"strings"
 
+	"github.com/hashicorp/terraform/addrs"
+
+	"github.com/hashicorp/hcl2/hcl/hclsyntax"
+
 	"github.com/hashicorp/hcl2/hcl"
 
 	"github.com/hashicorp/terraform/backend"
-	"github.com/hashicorp/terraform/config"
 	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/terraform"
 	"github.com/hashicorp/terraform/tfdiags"
@@ -57,24 +61,29 @@ func (c *ImportCommand) Run(args []string) int {
 		return 1
 	}
 
-	// Validate the provided resource address for syntax
-	addr, err := terraform.ParseResourceAddress(args[0])
-	if err != nil {
-		c.Ui.Error(fmt.Sprintf(importCommandInvalidAddressFmt, err))
+	var diags tfdiags.Diagnostics
+
+	// Parse the provided resource address.
+	traversal, travDiags := hclsyntax.ParseTraversalAbs([]byte(args[0]), "<import-address>", hcl.Pos{Line: 1, Column: 1})
+	diags = diags.Append(travDiags)
+	if travDiags.HasErrors() {
+		c.showDiagnostics(diags)
+		c.Ui.Info(importCommandInvalidAddressReference)
 		return 1
 	}
-	if !addr.HasResourceSpec() {
-		// module.foo target isn't allowed for import
-		c.Ui.Error(importCommandMissingResourceSpecMsg)
-		return 1
-	}
-	if addr.Mode != config.ManagedResourceMode {
-		// can't import to a data resource address
-		c.Ui.Error(importCommandResourceModeMsg)
+	addr, addrDiags := addrs.ParseAbsResourceInstance(traversal)
+	diags = diags.Append(addrDiags)
+	if addrDiags.HasErrors() {
+		c.showDiagnostics(diags)
+		c.Ui.Info(importCommandInvalidAddressReference)
 		return 1
 	}
 
-	var diags tfdiags.Diagnostics
+	if addr.Resource.Resource.Mode != addrs.ManagedResourceMode {
+		diags = diags.Append(errors.New("A managed resource address is required. Importing into a data resource is not allowed."))
+		c.showDiagnostics(diags)
+		return 1
+	}
 
 	if !c.dirIsConfigPath(configPath) {
 		diags = diags.Append(&hcl.Diagnostic{
@@ -102,9 +111,9 @@ func (c *ImportCommand) Run(args []string) int {
 	// This is to reduce the risk that a typo in the resource address will
 	// import something that Terraform will want to immediately destroy on
 	// the next plan, and generally acts as a reassurance of user intent.
-	targetConfig := config.Descendent(addr.Path)
+	targetConfig := config.DescendentForInstance(addr.Module)
 	if targetConfig == nil {
-		modulePath := addr.WholeModuleAddress().String()
+		modulePath := addr.Module.String()
 		diags = diags.Append(&hcl.Diagnostic{
 			Severity: hcl.DiagError,
 			Summary:  "Import to non-existent module",
@@ -118,15 +127,16 @@ func (c *ImportCommand) Run(args []string) int {
 	}
 	targetMod := targetConfig.Module
 	rcs := targetMod.ManagedResources
-	var rc *configs.ManagedResource
+	var rc *configs.Resource
+	resourceRelAddr := addr.Resource.Resource
 	for _, thisRc := range rcs {
-		if addr.MatchesManagedResourceConfig(addr.Path, thisRc) {
+		if resourceRelAddr.Type == thisRc.Type && resourceRelAddr.Name == thisRc.Name {
 			rc = thisRc
 			break
 		}
 	}
 	if !c.Meta.allowMissingConfig && rc == nil {
-		modulePath := addr.WholeModuleAddress().String()
+		modulePath := addr.Module.String()
 		if modulePath == "" {
 			modulePath = "the root module"
 		}
@@ -140,11 +150,33 @@ func (c *ImportCommand) Run(args []string) int {
 		// message.
 		c.Ui.Error(fmt.Sprintf(
 			importCommandMissingResourceFmt,
-			addr, modulePath, addr.Type, addr.Name,
+			addr, modulePath, resourceRelAddr.Type, resourceRelAddr.Name,
 		))
 		return 1
 	}
 
+	// Also parse the user-provided provider address, if any.
+	var providerAddr addrs.AbsProviderConfig
+	if c.Meta.provider != "" {
+		traversal, travDiags := hclsyntax.ParseTraversalAbs([]byte(c.Meta.provider), `-provider=...`, hcl.Pos{Line: 1, Column: 1})
+		diags = diags.Append(travDiags)
+		if travDiags.HasErrors() {
+			c.showDiagnostics(diags)
+			c.Ui.Info(importCommandInvalidAddressReference)
+			return 1
+		}
+		relAddr, addrDiags := addrs.ParseProviderConfigCompact(traversal)
+		diags = diags.Append(addrDiags)
+		if addrDiags.HasErrors() {
+			c.showDiagnostics(diags)
+			return 1
+		}
+		providerAddr = relAddr.Absolute(addrs.RootModuleInstance)
+	} else {
+		// Use a default address inferred from the resource type.
+		providerAddr = resourceRelAddr.DefaultProviderConfig().Absolute(addrs.RootModuleInstance)
+	}
+
 	// Check for user-supplied plugin path
 	if c.pluginPath, err = c.loadPluginPath(); err != nil {
 		c.Ui.Error(fmt.Sprintf("Error loading plugin path: %s", err))
@@ -200,17 +232,17 @@ func (c *ImportCommand) Run(args []string) int {
 	// Perform the import. Note that as you can see it is possible for this
 	// API to import more than one resource at once. For now, we only allow
 	// one while we stabilize this feature.
-	newState, err := ctx.Import(&terraform.ImportOpts{
+	newState, importDiags := ctx.Import(&terraform.ImportOpts{
 		Targets: []*terraform.ImportTarget{
 			&terraform.ImportTarget{
-				Addr:     args[0],
-				ID:       args[1],
-				Provider: c.Meta.provider,
+				Addr:         addr,
+				ID:           args[1],
+				ProviderAddr: providerAddr,
 			},
 		},
 	})
-	if err != nil {
-		diags = diags.Append(err)
+	diags = diags.Append(importDiags)
+	if diags.HasErrors() {
 		c.showDiagnostics(diags)
 		return 1
 	}
@@ -318,22 +350,8 @@ func (c *ImportCommand) Synopsis() string {
 	return "Import existing infrastructure into Terraform"
 }
 
-const importCommandInvalidAddressFmt = `Error: %s
-
-For information on valid syntax, see:
-https://www.terraform.io/docs/internals/resource-addressing.html
-`
-
-const importCommandMissingResourceSpecMsg = `Error: resource address must include a full resource spec
-
-For information on valid syntax, see:
-https://www.terraform.io/docs/internals/resource-addressing.html
-`
-
-const importCommandResourceModeMsg = `Error: resource address must refer to a managed resource.
-
-Data resources cannot be imported.
-`
+const importCommandInvalidAddressReference = `For information on valid syntax, see:
+https://www.terraform.io/docs/internals/resource-addressing.html`
 
 const importCommandMissingResourceFmt = `[reset][bold][red]Error:[reset][bold] resource address %q does not exist in the configuration.[reset]
 

command/init.go

@@ -396,20 +396,11 @@ func (c *InitCommand) getProviders(path string, state *terraform.State, upgrade
 		return diags
 	}
 
-	if err := terraform.CheckStateVersion(state); err != nil {
+	if err := terraform.CheckStateVersion(state, false); err != nil {
 		diags = diags.Append(err)
 		return diags
 	}
 
-	// FIXME: Restore this once terraform.CheckRequiredVersion is updated to
-	// work with a configs.Config instead of a legacy module.Tree.
-	/*
-		if err := terraform.CheckRequiredVersion(mod); err != nil {
-			diags = diags.Append(err)
-			return diags
-		}
-	*/
-
 	var available discovery.PluginMetaSet
 	if upgrade {
 		// If we're in upgrade mode, we ignore any auto-installed plugins

command/meta.go

@@ -12,19 +12,17 @@ import (
 	"log"
 	"os"
 	"path/filepath"
-	"sort"
 	"strconv"
 	"strings"
 	"time"
 
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/backend"
 	"github.com/hashicorp/terraform/backend/local"
 	"github.com/hashicorp/terraform/command/format"
-	"github.com/hashicorp/terraform/config"
 	"github.com/hashicorp/terraform/config/module"
 	"github.com/hashicorp/terraform/configs/configload"
 	"github.com/hashicorp/terraform/helper/experiment"
-	"github.com/hashicorp/terraform/helper/variables"
 	"github.com/hashicorp/terraform/helper/wrappedstreams"
 	"github.com/hashicorp/terraform/svchost/disco"
 	"github.com/hashicorp/terraform/terraform"
@@ -108,13 +106,11 @@ type Meta struct {
 	backendState *terraform.BackendState
 
 	// Variables for the context (private)
-	autoKey       string
-	autoVariables map[string]interface{}
-	input         bool
-	variables     map[string]interface{}
+	variableArgs rawFlags
+	input        bool
 
 	// Targets for this context (private)
-	targets []string
+	targets []addrs.Targetable
 
 	// Internal fields
 	color bool
@@ -325,18 +321,6 @@ func (m *Meta) contextOpts() *terraform.ContextOpts {
 	opts.Hooks = []terraform.Hook{m.uiHook(), &terraform.DebugHook{}}
 	opts.Hooks = append(opts.Hooks, m.ExtraHooks...)
 
-	vs := make(map[string]interface{})
-	for k, v := range opts.Variables {
-		vs[k] = v
-	}
-	for k, v := range m.autoVariables {
-		vs[k] = v
-	}
-	for k, v := range m.variables {
-		vs[k] = v
-	}
-	opts.Variables = vs
-
 	opts.Targets = m.targets
 	opts.UIInput = m.UIInput()
 	opts.Parallelism = m.parallelism
@@ -369,13 +353,15 @@ func (m *Meta) contextOpts() *terraform.ContextOpts {
 func (m *Meta) flagSet(n string) *flag.FlagSet {
 	f := flag.NewFlagSet(n, flag.ContinueOnError)
 	f.BoolVar(&m.input, "input", true, "input")
-	f.Var((*variables.Flag)(&m.variables), "var", "variables")
-	f.Var((*variables.FlagFile)(&m.variables), "var-file", "variable file")
-	f.Var((*FlagStringSlice)(&m.targets), "target", "resource to target")
+	f.Var((*FlagTargetSlice)(&m.targets), "target", "resource to target")
 
-	if m.autoKey != "" {
-		f.Var((*variables.FlagFile)(&m.autoVariables), m.autoKey, "variable file")
+	if m.variableArgs.items == nil {
+		m.variableArgs = newRawFlags("-var")
 	}
+	varValues := m.variableArgs.Alias("-var")
+	varFiles := m.variableArgs.Alias("-var-file")
+	f.Var(varValues, "var", "variables")
+	f.Var(varFiles, "var-file", "variable file")
 
 	// Advanced (don't need documentation, or unlikely to be set)
 	f.BoolVar(&m.shadow, "shadow", true, "shadow graph")
@@ -456,51 +442,6 @@ func (m *Meta) process(args []string, vars bool) ([]string, error) {
 		},
 	}
 
-	// If we support vars and the default var file exists, add it to
-	// the args...
-	m.autoKey = ""
-	if vars {
-		var preArgs []string
-
-		if _, err := os.Stat(DefaultVarsFilename); err == nil {
-			m.autoKey = "var-file-default"
-			preArgs = append(preArgs, "-"+m.autoKey, DefaultVarsFilename)
-		}
-
-		if _, err := os.Stat(DefaultVarsFilename + ".json"); err == nil {
-			m.autoKey = "var-file-default"
-			preArgs = append(preArgs, "-"+m.autoKey, DefaultVarsFilename+".json")
-		}
-
-		wd, err := os.Getwd()
-		if err != nil {
-			return nil, err
-		}
-
-		fis, err := ioutil.ReadDir(wd)
-		if err != nil {
-			return nil, err
-		}
-
-		// make sure we add the files in order
-		sort.Slice(fis, func(i, j int) bool {
-			return fis[i].Name() < fis[j].Name()
-		})
-
-		for _, fi := range fis {
-			name := fi.Name()
-			// Ignore directories, non-var-files, and ignored files
-			if fi.IsDir() || !isAutoVarFile(name) || config.IsIgnoredFile(name) {
-				continue
-			}
-
-			m.autoKey = "var-file-default"
-			preArgs = append(preArgs, "-"+m.autoKey, name)
-		}
-
-		args = append(preArgs, args...)
-	}
-
 	return args, nil
 }
 

command/meta_config.go

@@ -379,8 +379,10 @@ type rawFlags struct {
 }
 
 func newRawFlags(flagName string) rawFlags {
+	var items []rawFlag
 	return rawFlags{
 		flagName: flagName,
+		items:    &items,
 	}
 }
 

command/meta_new.go

@@ -167,7 +167,7 @@ func (m *Meta) Plan(path string) (*terraform.Plan, error) {
 	// We do a validation here that seems odd but if any plan is given,
 	// we must not have set any extra variables. The plan itself contains
 	// the variables and those aren't overwritten.
-	if len(m.variables) > 0 {
+	if len(m.variableArgs.AllItems()) > 0 {
 		return nil, fmt.Errorf(
 			"You can't set variables with the '-var' or '-var-file' flag\n" +
 				"when you're applying a plan file. The variables used when\n" +

command/output.go

@@ -8,6 +8,8 @@ import (
 	"sort"
 	"strings"
 
+	"github.com/hashicorp/terraform/addrs"
+
 	"github.com/hashicorp/terraform/tfdiags"
 )
 
@@ -72,14 +74,10 @@ func (c *OutputCommand) Run(args []string) int {
 		return 1
 	}
 
-	if module == "" {
-		module = "root"
-	} else {
-		module = "root." + module
-	}
-
-	// Get the proper module we want to get outputs for
-	modPath := strings.Split(module, ".")
+	// This command uses a legacy shorthand syntax for the module path that
+	// can't deal with keyed instances, so we'll just shim it for now and
+	// make the breaking change for this interface later.
+	modPath := addrs.Module(strings.Split(module, ".")).UnkeyedInstanceShim()
 
 	state := stateStore.State()
 	mod := state.ModuleByPath(modPath)

command/taint.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"strings"
 
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/command/clistate"
 	"github.com/hashicorp/terraform/terraform"
 )
@@ -107,8 +108,10 @@ func (c *TaintCommand) Run(args []string) int {
 		return 1
 	}
 
-	// Get the proper module we want to taint
-	modPath := strings.Split(module, ".")
+	// Get the ModuleState where we will taint. This is provided in a legacy
+	// string form that doesn't support module instance keys, so we'll shim
+	// it here.
+	modPath := addrs.Module(strings.Split(module, ".")).UnkeyedInstanceShim()
 	mod := s.ModuleByPath(modPath)
 	if mod == nil {
 		if allowMissing {

command/untaint.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"strings"
 
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/command/clistate"
 )
 
@@ -95,8 +96,10 @@ func (c *UntaintCommand) Run(args []string) int {
 		return 1
 	}
 
-	// Get the proper module holding the resource we want to untaint
-	modPath := strings.Split(module, ".")
+	// Get the ModuleState where we will untaint. This is provided in a legacy
+	// string form that doesn't support module instance keys, so we'll shim
+	// it here.
+	modPath := addrs.Module(strings.Split(module, ".")).UnkeyedInstanceShim()
 	mod := s.ModuleByPath(modPath)
 	if mod == nil {
 		if allowMissing {

command/validate.go

@@ -6,6 +6,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/hashicorp/terraform/terraform"
 	"github.com/hashicorp/terraform/tfdiags"
 )
 
@@ -111,36 +112,24 @@ Options:
 func (c *ValidateCommand) validate(dir string) tfdiags.Diagnostics {
 	var diags tfdiags.Diagnostics
 
-	_, cfgDiags := c.loadConfig(dir)
+	cfg, cfgDiags := c.loadConfig(dir)
 	diags = diags.Append(cfgDiags)
 
 	if diags.HasErrors() {
 		return diags
 	}
 
-	// TODO: run a validation walk once terraform.NewContext is updated
-	// to support new-style configuration.
-	/* old implementation of validation....
-	mod, modDiags := c.Module(dir)
-	diags = diags.Append(modDiags)
-	if modDiags.HasErrors() {
-		c.showDiagnostics(diags)
-		return 1
-	}
-
 	opts := c.contextOpts()
-	opts.Module = mod
+	opts.Config = cfg
 
-	tfCtx, err := terraform.NewContext(opts)
-	if err != nil {
-		diags = diags.Append(err)
-		c.showDiagnostics(diags)
-		return 1
+	tfCtx, ctxDiags := terraform.NewContext(opts)
+	diags = diags.Append(ctxDiags)
+	if ctxDiags.HasErrors() {
+		return diags
 	}
 
-	diags = diags.Append(tfCtx.Validate())
-	*/
-
+	validateDiags := tfCtx.Validate()
+	diags = diags.Append(validateDiags)
 	return diags
 }
 

dag/walk.go

@@ -388,10 +388,10 @@ func (w *Walker) walkVertex(v Vertex, info *walkerVertex) {
 	var diags tfdiags.Diagnostics
 	var upstreamFailed bool
 	if depsSuccess {
-		log.Printf("[TRACE] dag/walk: walking %q", VertexName(v))
+		log.Printf("[TRACE] dag/walk: visiting %q", VertexName(v))
 		diags = w.Callback(v)
 	} else {
-		log.Printf("[TRACE] dag/walk: upstream errored, not walking %q", VertexName(v))
+		log.Printf("[TRACE] dag/walk: upstream of %q errored, so skipping", VertexName(v))
 		// This won't be displayed to the user because we'll set upstreamFailed,
 		// but we need to ensure there's at least one error in here so that
 		// the failures will cascade downstream.
@@ -437,7 +437,7 @@ func (w *Walker) waitDeps(
 				return
 
 			case <-time.After(time.Second * 5):
-				log.Printf("[TRACE] dag/walk: vertex %q, waiting for: %q",
+				log.Printf("[TRACE] dag/walk: vertex %q is waiting for %q",
 					VertexName(v), VertexName(dep))
 			}
 		}

helper/resource/testing.go

@@ -14,11 +14,15 @@ import (
 	"syscall"
 	"testing"
 
+	"github.com/hashicorp/terraform/addrs"
+
+	"github.com/hashicorp/terraform/configs/configload"
+
 	"github.com/davecgh/go-spew/spew"
 	"github.com/hashicorp/errwrap"
 	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/logutils"
-	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/helper/logging"
 	"github.com/hashicorp/terraform/terraform"
 )
@@ -686,17 +690,17 @@ func testIDOnlyRefresh(c TestCase, opts terraform.ContextOpts, step TestStep, r
 	// doesn't have access to it and we may need things like provider
 	// configurations. The initial implementation of id-only checks used
 	// an empty config module, but that caused the aforementioned problems.
-	mod, err := testModule(opts, step)
+	cfg, err := testConfig(opts, step)
 	if err != nil {
 		return err
 	}
 
 	// Initialize the context
-	opts.Module = mod
+	opts.Config = cfg
 	opts.State = state
-	ctx, err := terraform.NewContext(&opts)
-	if err != nil {
-		return err
+	ctx, ctxDiags := terraform.NewContext(&opts)
+	if ctxDiags.HasErrors() {
+		return ctxDiags.Err()
 	}
 	if diags := ctx.Validate(); len(diags) > 0 {
 		if diags.HasErrors() {
@@ -707,9 +711,9 @@ func testIDOnlyRefresh(c TestCase, opts terraform.ContextOpts, step TestStep, r
 	}
 
 	// Refresh!
-	state, err = ctx.Refresh()
-	if err != nil {
-		return fmt.Errorf("Error refreshing: %s", err)
+	state, refreshDiags := ctx.Refresh()
+	if refreshDiags.HasErrors() {
+		return refreshDiags.Err()
 	}
 
 	// Verify attribute equivalence.
@@ -756,15 +760,14 @@ func testIDOnlyRefresh(c TestCase, opts terraform.ContextOpts, step TestStep, r
 	return nil
 }
 
-func testModule(opts terraform.ContextOpts, step TestStep) (*module.Tree, error) {
+func testConfig(opts terraform.ContextOpts, step TestStep) (*configs.Config, error) {
 	if step.PreConfig != nil {
 		step.PreConfig()
 	}
 
 	cfgPath, err := ioutil.TempDir("", "tf-test")
 	if err != nil {
-		return nil, fmt.Errorf(
-			"Error creating temporary directory for config: %s", err)
+		return nil, fmt.Errorf("Error creating temporary directory for config: %s", err)
 	}
 
 	if step.PreventDiskCleanup {
@@ -773,38 +776,37 @@ func testModule(opts terraform.ContextOpts, step TestStep) (*module.Tree, error)
 		defer os.RemoveAll(cfgPath)
 	}
 
-	// Write the configuration
-	cfgF, err := os.Create(filepath.Join(cfgPath, "main.tf"))
+	// Write the main configuration file
+	err = ioutil.WriteFile(filepath.Join(cfgPath, "main.tf"), []byte(step.Config), os.ModePerm)
 	if err != nil {
-		return nil, fmt.Errorf(
-			"Error creating temporary file for config: %s", err)
+		return nil, fmt.Errorf("Error creating temporary file for config: %s", err)
 	}
 
-	_, err = io.Copy(cfgF, strings.NewReader(step.Config))
-	cfgF.Close()
+	// Create directory for our child modules, if any.
+	modulesDir := filepath.Join(cfgPath, ".modules")
+	err = os.Mkdir(modulesDir, os.ModePerm)
 	if err != nil {
-		return nil, fmt.Errorf(
-			"Error creating temporary file for config: %s", err)
+		return nil, fmt.Errorf("Error creating child modules directory: %s", err)
 	}
 
-	// Parse the configuration
-	mod, err := module.NewTreeModule("", cfgPath)
+	loader, err := configload.NewLoader(&configload.Config{
+		ModulesDir: modulesDir,
+	})
 	if err != nil {
-		return nil, fmt.Errorf(
-			"Error loading configuration: %s", err)
+		return nil, fmt.Errorf("failed to create config loader: %s", err)
 	}
 
-	// Load the modules
-	modStorage := &module.Storage{
-		StorageDir: filepath.Join(cfgPath, ".tfmodules"),
-		Mode:       module.GetModeGet,
-	}
-	err = mod.Load(modStorage)
-	if err != nil {
-		return nil, fmt.Errorf("Error downloading modules: %s", err)
+	installDiags := loader.InstallModules(cfgPath, true, configload.InstallHooksImpl{})
+	if installDiags.HasErrors() {
+		return nil, installDiags
 	}
 
-	return mod, nil
+	config, configDiags := loader.LoadConfig(cfgPath)
+	if configDiags.HasErrors() {
+		return nil, configDiags
+	}
+
+	return config, nil
 }
 
 func testResource(c TestStep, state *terraform.State) (*terraform.ResourceState, error) {
@@ -881,8 +883,9 @@ func TestCheckResourceAttrSet(name, key string) TestCheckFunc {
 // TestCheckModuleResourceAttrSet - as per TestCheckResourceAttrSet but with
 // support for non-root modules
 func TestCheckModuleResourceAttrSet(mp []string, name string, key string) TestCheckFunc {
+	mpt := addrs.Module(mp).UnkeyedInstanceShim()
 	return func(s *terraform.State) error {
-		is, err := modulePathPrimaryInstanceState(s, mp, name)
+		is, err := modulePathPrimaryInstanceState(s, mpt, name)
 		if err != nil {
 			return err
 		}
@@ -915,8 +918,9 @@ func TestCheckResourceAttr(name, key, value string) TestCheckFunc {
 // TestCheckModuleResourceAttr - as per TestCheckResourceAttr but with
 // support for non-root modules
 func TestCheckModuleResourceAttr(mp []string, name string, key string, value string) TestCheckFunc {
+	mpt := addrs.Module(mp).UnkeyedInstanceShim()
 	return func(s *terraform.State) error {
-		is, err := modulePathPrimaryInstanceState(s, mp, name)
+		is, err := modulePathPrimaryInstanceState(s, mpt, name)
 		if err != nil {
 			return err
 		}
@@ -957,8 +961,9 @@ func TestCheckNoResourceAttr(name, key string) TestCheckFunc {
 // TestCheckModuleNoResourceAttr - as per TestCheckNoResourceAttr but with
 // support for non-root modules
 func TestCheckModuleNoResourceAttr(mp []string, name string, key string) TestCheckFunc {
+	mpt := addrs.Module(mp).UnkeyedInstanceShim()
 	return func(s *terraform.State) error {
-		is, err := modulePathPrimaryInstanceState(s, mp, name)
+		is, err := modulePathPrimaryInstanceState(s, mpt, name)
 		if err != nil {
 			return err
 		}
@@ -991,8 +996,9 @@ func TestMatchResourceAttr(name, key string, r *regexp.Regexp) TestCheckFunc {
 // TestModuleMatchResourceAttr - as per TestMatchResourceAttr but with
 // support for non-root modules
 func TestModuleMatchResourceAttr(mp []string, name string, key string, r *regexp.Regexp) TestCheckFunc {
+	mpt := addrs.Module(mp).UnkeyedInstanceShim()
 	return func(s *terraform.State) error {
-		is, err := modulePathPrimaryInstanceState(s, mp, name)
+		is, err := modulePathPrimaryInstanceState(s, mpt, name)
 		if err != nil {
 			return err
 		}
@@ -1052,13 +1058,15 @@ func TestCheckResourceAttrPair(nameFirst, keyFirst, nameSecond, keySecond string
 // TestCheckModuleResourceAttrPair - as per TestCheckResourceAttrPair but with
 // support for non-root modules
 func TestCheckModuleResourceAttrPair(mpFirst []string, nameFirst string, keyFirst string, mpSecond []string, nameSecond string, keySecond string) TestCheckFunc {
+	mptFirst := addrs.Module(mpFirst).UnkeyedInstanceShim()
+	mptSecond := addrs.Module(mpSecond).UnkeyedInstanceShim()
 	return func(s *terraform.State) error {
-		isFirst, err := modulePathPrimaryInstanceState(s, mpFirst, nameFirst)
+		isFirst, err := modulePathPrimaryInstanceState(s, mptFirst, nameFirst)
 		if err != nil {
 			return err
 		}
 
-		isSecond, err := modulePathPrimaryInstanceState(s, mpSecond, nameSecond)
+		isSecond, err := modulePathPrimaryInstanceState(s, mptSecond, nameSecond)
 		if err != nil {
 			return err
 		}
@@ -1163,7 +1171,7 @@ func modulePrimaryInstanceState(s *terraform.State, ms *terraform.ModuleState, n
 
 // modulePathPrimaryInstanceState returns the primary instance state for the
 // given resource name in a given module path.
-func modulePathPrimaryInstanceState(s *terraform.State, mp []string, name string) (*terraform.InstanceState, error) {
+func modulePathPrimaryInstanceState(s *terraform.State, mp addrs.ModuleInstance, name string) (*terraform.InstanceState, error) {
 	ms := s.ModuleByPath(mp)
 	if ms == nil {
 		return nil, fmt.Errorf("No module found at: %s", mp)

helper/resource/testing_config.go

@@ -6,6 +6,8 @@ import (
 	"log"
 	"strings"
 
+	"github.com/hashicorp/terraform/tfdiags"
+
 	"github.com/hashicorp/errwrap"
 	"github.com/hashicorp/terraform/terraform"
 )
@@ -30,41 +32,41 @@ func testStep(
 		}
 	}
 
-	mod, err := testModule(opts, step)
+	cfg, err := testConfig(opts, step)
 	if err != nil {
 		return state, err
 	}
 
+	var stepDiags tfdiags.Diagnostics
+
 	// Build the context
-	opts.Module = mod
+	opts.Config = cfg
 	opts.State = state
 	opts.Destroy = step.Destroy
-	ctx, err := terraform.NewContext(&opts)
-	if err != nil {
-		return state, fmt.Errorf("Error initializing context: %s", err)
+	ctx, stepDiags := terraform.NewContext(&opts)
+	if stepDiags.HasErrors() {
+		return state, fmt.Errorf("Error initializing context: %s", stepDiags.Err())
 	}
-	if diags := ctx.Validate(); len(diags) > 0 {
-		if diags.HasErrors() {
-			return nil, errwrap.Wrapf("config is invalid: {{err}}", diags.Err())
+	if stepDiags := ctx.Validate(); len(stepDiags) > 0 {
+		if stepDiags.HasErrors() {
+			return nil, errwrap.Wrapf("config is invalid: {{err}}", stepDiags.Err())
 		}
 
-		log.Printf("[WARN] Config warnings:\n%s", diags)
+		log.Printf("[WARN] Config warnings:\n%s", stepDiags)
 	}
 
 	// Refresh!
-	state, err = ctx.Refresh()
-	if err != nil {
-		return state, fmt.Errorf(
-			"Error refreshing: %s", err)
+	state, stepDiags = ctx.Refresh()
+	if stepDiags.HasErrors() {
+		return state, fmt.Errorf("Error refreshing: %s", stepDiags.Err())
 	}
 
 	// If this step is a PlanOnly step, skip over this first Plan and subsequent
 	// Apply, and use the follow up Plan that checks for perpetual diffs
 	if !step.PlanOnly {
 		// Plan!
-		if p, err := ctx.Plan(); err != nil {
-			return state, fmt.Errorf(
-				"Error planning: %s", err)
+		if p, stepDiags := ctx.Plan(); stepDiags.HasErrors() {
+			return state, fmt.Errorf("Error planning: %s", stepDiags.Err())
 		} else {
 			log.Printf("[WARN] Test: Step plan: %s", p)
 		}
@@ -74,13 +76,13 @@ func testStep(
 		// function
 		stateBeforeApplication := state.DeepCopy()
 
-		// Apply!
-		state, err = ctx.Apply()
-		if err != nil {
-			return state, fmt.Errorf("Error applying: %s", err)
+		// Apply the diff, creating real resources.
+		state, stepDiags = ctx.Apply()
+		if stepDiags.HasErrors() {
+			return state, fmt.Errorf("Error applying: %s", stepDiags.Err())
 		}
 
-		// Check! Excitement!
+		// Run any configured checks
 		if step.Check != nil {
 			if step.Destroy {
 				if err := step.Check(stateBeforeApplication); err != nil {
@@ -97,8 +99,8 @@ func testStep(
 	// Now, verify that Plan is now empty and we don't have a perpetual diff issue
 	// We do this with TWO plans. One without a refresh.
 	var p *terraform.Plan
-	if p, err = ctx.Plan(); err != nil {
-		return state, fmt.Errorf("Error on follow-up plan: %s", err)
+	if p, stepDiags = ctx.Plan(); stepDiags.HasErrors() {
+		return state, fmt.Errorf("Error on follow-up plan: %s", stepDiags.Err())
 	}
 	if p.Diff != nil && !p.Diff.Empty() {
 		if step.ExpectNonEmptyPlan {
@@ -111,14 +113,13 @@ func testStep(
 
 	// And another after a Refresh.
 	if !step.Destroy || (step.Destroy && !step.PreventPostDestroyRefresh) {
-		state, err = ctx.Refresh()
-		if err != nil {
-			return state, fmt.Errorf(
-				"Error on follow-up refresh: %s", err)
+		state, stepDiags = ctx.Refresh()
+		if stepDiags.HasErrors() {
+			return state, fmt.Errorf("Error on follow-up refresh: %s", stepDiags.Err())
 		}
 	}
-	if p, err = ctx.Plan(); err != nil {
-		return state, fmt.Errorf("Error on second follow-up plan: %s", err)
+	if p, stepDiags = ctx.Plan(); stepDiags.HasErrors() {
+		return state, fmt.Errorf("Error on second follow-up plan: %s", stepDiags.Err())
 	}
 	empty := p.Diff == nil || p.Diff.Empty()
 

helper/resource/testing_import_state.go

@@ -6,6 +6,11 @@ import (
 	"reflect"
 	"strings"
 
+	"github.com/hashicorp/terraform/addrs"
+
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/hcl2/hcl/hclsyntax"
+
 	"github.com/davecgh/go-spew/spew"
 	"github.com/hashicorp/terraform/terraform"
 )
@@ -41,33 +46,45 @@ func testStepImportState(
 
 	// Setup the context. We initialize with an empty state. We use the
 	// full config for provider configurations.
-	mod, err := testModule(opts, step)
+	cfg, err := testConfig(opts, step)
 	if err != nil {
 		return state, err
 	}
 
-	opts.Module = mod
+	opts.Config = cfg
 	opts.State = terraform.NewState()
-	ctx, err := terraform.NewContext(&opts)
-	if err != nil {
-		return state, err
+	ctx, stepDiags := terraform.NewContext(&opts)
+	if stepDiags.HasErrors() {
+		return state, stepDiags.Err()
 	}
 
-	// Do the import!
-	newState, err := ctx.Import(&terraform.ImportOpts{
+	// The test step provides the resource address as a string, so we need
+	// to parse it to get an addrs.AbsResourceAddress to pass in to the
+	// import method.
+	traversal, hclDiags := hclsyntax.ParseTraversalAbs([]byte(step.ResourceName), "", hcl.Pos{})
+	if hclDiags.HasErrors() {
+		return nil, hclDiags
+	}
+	importAddr, stepDiags := addrs.ParseAbsResourceInstance(traversal)
+	if stepDiags.HasErrors() {
+		return nil, stepDiags.Err()
+	}
+
+	// Do the import
+	newState, stepDiags := ctx.Import(&terraform.ImportOpts{
 		// Set the module so that any provider config is loaded
-		Module: mod,
+		Config: cfg,
 
 		Targets: []*terraform.ImportTarget{
 			&terraform.ImportTarget{
-				Addr: step.ResourceName,
+				Addr: importAddr,
 				ID:   importId,
 			},
 		},
 	})
-	if err != nil {
-		log.Printf("[ERROR] Test: ImportState failure: %s", err)
-		return state, err
+	if stepDiags.HasErrors() {
+		log.Printf("[ERROR] Test: ImportState failure: %s", stepDiags.Err())
+		return state, stepDiags.Err()
 	}
 
 	// Go through the new state and verify

helper/schema/provisioner.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/config/configschema"
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -121,6 +122,11 @@ func (p *Provisioner) Stop() error {
 	return nil
 }
 
+// GetConfigSchema implementation of terraform.ResourceProvisioner interface.
+func (p *Provisioner) GetConfigSchema() (*configschema.Block, error) {
+	return schemaMap(p.Schema).CoreConfigSchema(), nil
+}
+
 // Apply implementation of terraform.ResourceProvisioner interface.
 func (p *Provisioner) Apply(
 	o terraform.UIOutput,

lang/data.go

@@ -26,7 +26,6 @@ type Data interface {
 	GetModuleInstance(addrs.ModuleCallInstance, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics)
 	GetModuleInstanceOutput(addrs.ModuleCallOutput, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics)
 	GetPathAttr(addrs.PathAttr, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics)
-	GetSelf(tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics)
 	GetTerraformAttr(addrs.TerraformAttr, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics)
 	GetInputVariable(addrs.InputVariable, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics)
 }

lang/data_test.go

@@ -12,7 +12,6 @@ type dataForTests struct {
 	LocalValues       map[string]cty.Value
 	Modules           map[string]cty.Value
 	PathAttrs         map[string]cty.Value
-	Self              cty.Value
 	TerraformAttrs    map[string]cty.Value
 	InputVariables    map[string]cty.Value
 }
@@ -49,10 +48,6 @@ func (d *dataForTests) GetPathAttr(addr addrs.PathAttr, rng tfdiags.SourceRange)
 	return d.PathAttrs[addr.Name], nil
 }
 
-func (d *dataForTests) GetSelf(rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
-	return d.Self, nil
-}
-
 func (d *dataForTests) GetTerraformAttr(addr addrs.TerraformAttr, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
 	return d.TerraformAttrs[addr.Name], nil
 }

lang/eval.go

@@ -93,6 +93,44 @@ func (s *Scope) EvalExpr(expr hcl.Expression, wantType cty.Type) (cty.Value, tfd
 	return val, diags
 }
 
+// EvalReference evaluates the given reference in the receiving scope and
+// returns the resulting value. The value will be converted to the given type before
+// it is returned if possible, or else an error diagnostic will be produced
+// describing the conversion error.
+//
+// Pass an expected type of cty.DynamicPseudoType to skip automatic conversion
+// and just obtain the returned value directly.
+//
+// If the returned diagnostics contains errors then the result may be
+// incomplete, but will always be of the requested type.
+func (s *Scope) EvalReference(ref *addrs.Reference, wantType cty.Type) (cty.Value, tfdiags.Diagnostics) {
+	var diags tfdiags.Diagnostics
+
+	// We cheat a bit here and just build an EvalContext for our requested
+	// reference with the "self" address overridden, and then pull the "self"
+	// result out of it to return.
+	ctx, ctxDiags := s.evalContext([]*addrs.Reference{ref}, ref.Subject)
+	diags = diags.Append(ctxDiags)
+	val := ctx.Variables["self"]
+	if val == cty.NilVal {
+		val = cty.DynamicVal
+	}
+
+	var convErr error
+	val, convErr = convert.Convert(val, wantType)
+	if convErr != nil {
+		val = cty.UnknownVal(wantType)
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Incorrect value type",
+			Detail:   fmt.Sprintf("Invalid expression value: %s.", tfdiags.FormatError(convErr)),
+			Subject:  ref.SourceRange.ToHCL().Ptr(),
+		})
+	}
+
+	return val, diags
+}
+
 // EvalContext constructs a HCL expression evaluation context whose variable
 // scope contains sufficient values to satisfy the given set of references.
 //
@@ -100,6 +138,10 @@ func (s *Scope) EvalExpr(expr hcl.Expression, wantType cty.Type) (cty.Value, tfd
 // this type offers, but this is here for less common situations where the
 // caller will handle the evaluation calls itself.
 func (s *Scope) EvalContext(refs []*addrs.Reference) (*hcl.EvalContext, tfdiags.Diagnostics) {
+	return s.evalContext(refs, s.SelfAddr)
+}
+
+func (s *Scope) evalContext(refs []*addrs.Reference, selfAddr addrs.Referenceable) (*hcl.EvalContext, tfdiags.Diagnostics) {
 	var diags tfdiags.Diagnostics
 	vals := make(map[string]cty.Value)
 	funcs := s.Functions()
@@ -134,17 +176,37 @@ func (s *Scope) EvalContext(refs []*addrs.Reference) (*hcl.EvalContext, tfdiags.
 
 	for _, ref := range refs {
 		rng := ref.SourceRange
+		isSelf := false
 
-		if ref.Subject == addrs.Self {
-			val, valDiags := normalizeRefValue(s.Data.GetSelf(ref.SourceRange))
-			diags = diags.Append(valDiags)
-			self = val
-			continue
+		rawSubj := ref.Subject
+		if rawSubj == addrs.Self {
+			if selfAddr == nil {
+				diags = diags.Append(&hcl.Diagnostic{
+					Severity: hcl.DiagError,
+					Summary:  `Invalid "self" reference`,
+					// This detail message mentions some current practice that
+					// this codepath doesn't really "know about". If the "self"
+					// object starts being supported in more contexts later then
+					// we'll need to adjust this message.
+					Detail:  `The "self" object is not available in this context. This object can be used only in resource provisioner and connection blocks.`,
+					Subject: ref.SourceRange.ToHCL().Ptr(),
+				})
+				continue
+			}
+
+			// Treat "self" as an alias for the configured self address.
+			rawSubj = selfAddr
+			isSelf = true
+
+			if rawSubj == addrs.Self {
+				// Programming error: the self address cannot alias itself.
+				panic("scope SelfAddr attempting to alias itself")
+			}
 		}
 
 		// This type switch must cover all of the "Referenceable" implementations
 		// in package addrs.
-		switch subj := ref.Subject.(type) {
+		switch subj := rawSubj.(type) {
 
 		case addrs.ResourceInstance:
 			var into map[string]map[string]map[addrs.InstanceKey]cty.Value
@@ -168,6 +230,9 @@ func (s *Scope) EvalContext(refs []*addrs.Reference) (*hcl.EvalContext, tfdiags.
 				into[r.Type][r.Name] = make(map[addrs.InstanceKey]cty.Value)
 			}
 			into[r.Type][r.Name][subj.Key] = val
+			if isSelf {
+				self = val
+			}
 
 		case addrs.ModuleCallInstance:
 			val, valDiags := normalizeRefValue(s.Data.GetModuleInstance(subj, rng))
@@ -177,6 +242,9 @@ func (s *Scope) EvalContext(refs []*addrs.Reference) (*hcl.EvalContext, tfdiags.
 				wholeModules[subj.Call.Name] = make(map[addrs.InstanceKey]cty.Value)
 			}
 			wholeModules[subj.Call.Name][subj.Key] = val
+			if isSelf {
+				self = val
+			}
 
 		case addrs.ModuleCallOutput:
 			val, valDiags := normalizeRefValue(s.Data.GetModuleInstanceOutput(subj, rng))
@@ -191,35 +259,53 @@ func (s *Scope) EvalContext(refs []*addrs.Reference) (*hcl.EvalContext, tfdiags.
 				moduleOutputs[callName][callKey] = make(map[string]cty.Value)
 			}
 			moduleOutputs[callName][callKey][subj.Name] = val
+			if isSelf {
+				self = val
+			}
 
 		case addrs.InputVariable:
 			val, valDiags := normalizeRefValue(s.Data.GetInputVariable(subj, rng))
 			diags = diags.Append(valDiags)
 			inputVariables[subj.Name] = val
+			if isSelf {
+				self = val
+			}
 
 		case addrs.LocalValue:
 			val, valDiags := normalizeRefValue(s.Data.GetLocalValue(subj, rng))
 			diags = diags.Append(valDiags)
 			localValues[subj.Name] = val
+			if isSelf {
+				self = val
+			}
 
 		case addrs.PathAttr:
 			val, valDiags := normalizeRefValue(s.Data.GetPathAttr(subj, rng))
 			diags = diags.Append(valDiags)
 			pathAttrs[subj.Name] = val
+			if isSelf {
+				self = val
+			}
 
 		case addrs.TerraformAttr:
 			val, valDiags := normalizeRefValue(s.Data.GetTerraformAttr(subj, rng))
 			diags = diags.Append(valDiags)
 			terraformAttrs[subj.Name] = val
+			if isSelf {
+				self = val
+			}
 
 		case addrs.CountAttr:
 			val, valDiags := normalizeRefValue(s.Data.GetCountAttr(subj, rng))
 			diags = diags.Append(valDiags)
 			countAttrs[subj.Name] = val
+			if isSelf {
+				self = val
+			}
 
 		default:
 			// Should never happen
-			panic(fmt.Errorf("Scope.buildEvalContext cannot handle address type %T", ref.Subject))
+			panic(fmt.Errorf("Scope.buildEvalContext cannot handle address type %T", rawSubj))
 		}
 	}
 

lang/eval_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"testing"
 
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/config/configschema"
 
 	"github.com/hashicorp/hcl2/hcl"
@@ -50,9 +51,6 @@ func TestScopeEvalContext(t *testing.T) {
 		PathAttrs: map[string]cty.Value{
 			"module": cty.StringVal("foo/bar"),
 		},
-		Self: cty.ObjectVal(map[string]cty.Value{
-			"is_self": cty.True,
-		}),
 		TerraformAttrs: map[string]cty.Value{
 			"workspace": cty.StringVal("default"),
 		},
@@ -192,8 +190,19 @@ func TestScopeEvalContext(t *testing.T) {
 		{
 			`self.baz`,
 			map[string]cty.Value{
+				// In the test function below we set "SelfAddr" to be
+				// one of the resources in our dataset, causing it to get
+				// expanded here and then copied into "self".
+				"null_resource": cty.ObjectVal(map[string]cty.Value{
+					"multi": cty.TupleVal([]cty.Value{
+						cty.DynamicVal,
+						cty.ObjectVal(map[string]cty.Value{
+							"attr": cty.StringVal("multi1"),
+						}),
+					}),
+				}),
 				"self": cty.ObjectVal(map[string]cty.Value{
-					"is_self": cty.True,
+					"attr": cty.StringVal("multi1"),
 				}),
 			},
 		},
@@ -233,6 +242,17 @@ func TestScopeEvalContext(t *testing.T) {
 
 			scope := &Scope{
 				Data: data,
+
+				// "self" will just be an arbitrary one of the several resource
+				// instances we have in our test dataset.
+				SelfAddr: addrs.ResourceInstance{
+					Resource: addrs.Resource{
+						Mode: addrs.ManagedResourceMode,
+						Type: "null_resource",
+						Name: "multi",
+					},
+					Key: addrs.IntKey(1),
+				},
 			}
 			ctx, ctxDiags := scope.EvalContext(refs)
 			if ctxDiags.HasErrors() {

lang/references.go

@@ -48,6 +48,9 @@ func References(traversals []hcl.Traversal) ([]*addrs.Reference, tfdiags.Diagnos
 // A block schema must be provided so that this function can determine where in
 // the body variables are expected.
 func ReferencesInBlock(body hcl.Body, schema *configschema.Block) ([]*addrs.Reference, tfdiags.Diagnostics) {
+	if body == nil {
+		return nil, nil
+	}
 	spec := schema.DecoderSpec()
 	traversals := hcldec.Variables(body, spec)
 	return References(traversals)
@@ -57,6 +60,9 @@ func ReferencesInBlock(body hcl.Body, schema *configschema.Block) ([]*addrs.Refe
 // the given expression for traversals, before converting those traversals
 // to references.
 func ReferencesInExpr(expr hcl.Expression) ([]*addrs.Reference, tfdiags.Diagnostics) {
+	if expr == nil {
+		return nil, nil
+	}
 	traversals := expr.Variables()
 	return References(traversals)
 }

lang/scope.go

@@ -4,6 +4,8 @@ import (
 	"sync"
 
 	"github.com/zclconf/go-cty/cty/function"
+
+	"github.com/hashicorp/terraform/addrs"
 )
 
 // Scope is the main type in this package, allowing dynamic evaluation of
@@ -13,6 +15,10 @@ type Scope struct {
 	// Data is used to resolve references in expressions.
 	Data Data
 
+	// SelfAddr is the address that the "self" object should be an alias of,
+	// or nil if the "self" object should not be available at all.
+	SelfAddr addrs.Referenceable
+
 	// BaseDir is the base directory used by any interpolation functions that
 	// accept filesystem paths as arguments.
 	BaseDir string

terraform/context.go

@@ -8,12 +8,14 @@ import (
 	"strings"
 	"sync"
 
-	"github.com/hashicorp/terraform/tfdiags"
+	"github.com/hashicorp/terraform/addrs"
+
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/tfdiags"
+	"github.com/zclconf/go-cty/cty"
 
-	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/hcl"
 	"github.com/hashicorp/terraform/config"
-	"github.com/hashicorp/terraform/config/module"
 	"github.com/hashicorp/terraform/version"
 )
 
@@ -55,15 +57,15 @@ type ContextOpts struct {
 	Destroy            bool
 	Diff               *Diff
 	Hooks              []Hook
-	Module             *module.Tree
+	Config             *configs.Config
 	Parallelism        int
 	State              *State
 	StateFutureAllowed bool
 	ProviderResolver   ResourceProviderResolver
 	Provisioners       map[string]ResourceProvisionerFactory
 	Shadow             bool
-	Targets            []string
-	Variables          map[string]interface{}
+	Targets            []addrs.Targetable
+	Variables          InputValues
 
 	// If non-nil, will apply as additional constraints on the provider
 	// plugins that will be requested from the provider resolver.
@@ -97,18 +99,18 @@ type Context struct {
 	diffLock   sync.RWMutex
 	hooks      []Hook
 	meta       *ContextMeta
-	module     *module.Tree
+	config     *configs.Config
 	sh         *stopHook
 	shadow     bool
 	state      *State
 	stateLock  sync.RWMutex
-	targets    []string
+	targets    []addrs.Targetable
 	uiInput    UIInput
-	variables  map[string]interface{}
+	variables  InputValues
 
 	l                   sync.Mutex // Lock acquired during any task
 	parallelSem         Semaphore
-	providerInputConfig map[string]map[string]interface{}
+	providerInputConfig map[string]map[string]cty.Value
 	providerSHA256s     map[string][]byte
 	runLock             sync.Mutex
 	runCond             *sync.Cond
@@ -119,15 +121,18 @@ type Context struct {
 
 // NewContext creates a new Context structure.
 //
-// Once a Context is creator, the pointer values within ContextOpts
-// should not be mutated in any way, since the pointers are copied, not
-// the values themselves.
-func NewContext(opts *ContextOpts) (*Context, error) {
-	// Validate the version requirement if it is given
-	if opts.Module != nil {
-		if err := CheckRequiredVersion(opts.Module); err != nil {
-			return nil, err
-		}
+// Once a Context is created, the caller should not access or mutate any of
+// the objects referenced (directly or indirectly) by the ContextOpts fields.
+//
+// If the returned diagnostics contains errors then the resulting context is
+// invalid and must not be used.
+func NewContext(opts *ContextOpts) (*Context, tfdiags.Diagnostics) {
+	diags := CheckCoreVersionRequirements(opts.Config)
+	// If version constraints are not met then we'll bail early since otherwise
+	// we're likely to just see a bunch of other errors related to
+	// incompatibilities, which could be overwhelming for the user.
+	if diags.HasErrors() {
+		return nil, diags
 	}
 
 	// Copy all the hooks and add our stop hook. We don't append directly
@@ -145,8 +150,9 @@ func NewContext(opts *ContextOpts) (*Context, error) {
 
 	// If our state is from the future, then error. Callers can avoid
 	// this error by explicitly setting `StateFutureAllowed`.
-	if err := CheckStateVersion(state); err != nil && !opts.StateFutureAllowed {
-		return nil, err
+	if stateDiags := CheckStateVersion(state, opts.StateFutureAllowed); stateDiags.HasErrors() {
+		diags = diags.Append(stateDiags)
+		return nil, diags
 	}
 
 	// Explicitly reset our state version to our current version so that
@@ -168,27 +174,28 @@ func NewContext(opts *ContextOpts) (*Context, error) {
 	//    2 - Take values specified in -var flags, overriding values
 	//        set by environment variables if necessary. This includes
 	//        values taken from -var-file in addition.
-	variables := make(map[string]interface{})
-	if opts.Module != nil {
-		var err error
-		variables, err = Variables(opts.Module, opts.Variables)
-		if err != nil {
-			return nil, err
-		}
+	var variables InputValues
+	if opts.Config != nil {
+		// Default variables from the configuration seed our map.
+		variables = DefaultVariableValues(opts.Config.Module.Variables)
 	}
+	// Variables provided by the caller (from CLI, environment, etc) can
+	// override the defaults.
+	variables = variables.Override(opts.Variables)
 
 	// Bind available provider plugins to the constraints in config
 	var providers map[string]ResourceProviderFactory
 	if opts.ProviderResolver != nil {
 		var err error
-		deps := ModuleTreeDependencies(opts.Module, state)
+		deps := ConfigTreeDependencies(opts.Config, state)
 		reqd := deps.AllPluginRequirements()
 		if opts.ProviderSHA256s != nil && !opts.SkipProviderVerify {
 			reqd.LockExecutables(opts.ProviderSHA256s)
 		}
 		providers, err = resourceProviderFactories(opts.ProviderResolver, reqd)
 		if err != nil {
-			return nil, err
+			diags = diags.Append(err)
+			return nil, diags
 		}
 	} else {
 		providers = make(map[string]ResourceProviderFactory)
@@ -208,7 +215,7 @@ func NewContext(opts *ContextOpts) (*Context, error) {
 		diff:      diff,
 		hooks:     hooks,
 		meta:      opts.Meta,
-		module:    opts.Module,
+		config:    opts.Config,
 		shadow:    opts.Shadow,
 		state:     state,
 		targets:   opts.Targets,
@@ -216,7 +223,7 @@ func NewContext(opts *ContextOpts) (*Context, error) {
 		variables: variables,
 
 		parallelSem:         NewSemaphore(par),
-		providerInputConfig: make(map[string]map[string]interface{}),
+		providerInputConfig: make(map[string]map[string]cty.Value),
 		providerSHA256s:     opts.ProviderSHA256s,
 		sh:                  sh,
 	}, nil
@@ -233,7 +240,7 @@ type ContextGraphOpts struct {
 // Graph returns the graph used for the given operation type.
 //
 // The most extensive or complex graph type is GraphTypePlan.
-func (c *Context) Graph(typ GraphType, opts *ContextGraphOpts) (*Graph, error) {
+func (c *Context) Graph(typ GraphType, opts *ContextGraphOpts) (*Graph, tfdiags.Diagnostics) {
 	if opts == nil {
 		opts = &ContextGraphOpts{Validate: true}
 	}
@@ -242,7 +249,7 @@ func (c *Context) Graph(typ GraphType, opts *ContextGraphOpts) (*Graph, error) {
 	switch typ {
 	case GraphTypeApply:
 		return (&ApplyGraphBuilder{
-			Module:       c.module,
+			Config:       c.config,
 			Diff:         c.diff,
 			State:        c.state,
 			Providers:    c.components.ResourceProviders(),
@@ -250,7 +257,7 @@ func (c *Context) Graph(typ GraphType, opts *ContextGraphOpts) (*Graph, error) {
 			Targets:      c.targets,
 			Destroy:      c.destroy,
 			Validate:     opts.Validate,
-		}).Build(RootModulePath)
+		}).Build(addrs.RootModuleInstance)
 
 	case GraphTypeInput:
 		// The input graph is just a slightly modified plan graph
@@ -261,7 +268,7 @@ func (c *Context) Graph(typ GraphType, opts *ContextGraphOpts) (*Graph, error) {
 	case GraphTypePlan:
 		// Create the plan graph builder
 		p := &PlanGraphBuilder{
-			Module:    c.module,
+			Config:    c.config,
 			State:     c.state,
 			Providers: c.components.ResourceProviders(),
 			Targets:   c.targets,
@@ -280,27 +287,29 @@ func (c *Context) Graph(typ GraphType, opts *ContextGraphOpts) (*Graph, error) {
 			b = ValidateGraphBuilder(p)
 		}
 
-		return b.Build(RootModulePath)
+		return b.Build(addrs.RootModuleInstance)
 
 	case GraphTypePlanDestroy:
 		return (&DestroyPlanGraphBuilder{
-			Module:   c.module,
+			Config:   c.config,
 			State:    c.state,
 			Targets:  c.targets,
 			Validate: opts.Validate,
-		}).Build(RootModulePath)
+		}).Build(addrs.RootModuleInstance)
 
 	case GraphTypeRefresh:
 		return (&RefreshGraphBuilder{
-			Module:    c.module,
+			Config:    c.config,
 			State:     c.state,
 			Providers: c.components.ResourceProviders(),
 			Targets:   c.targets,
 			Validate:  opts.Validate,
-		}).Build(RootModulePath)
-	}
+		}).Build(addrs.RootModuleInstance)
 
-	return nil, fmt.Errorf("unknown graph type: %s", typ)
+	default:
+		// Should never happen, because the above is exhaustive for all graph types.
+		panic(fmt.Errorf("unsupported graph type %s", typ))
+	}
 }
 
 // ShadowError returns any errors caught during a shadow operation.
@@ -337,99 +346,91 @@ func (c *Context) State() *State {
 	return c.state.DeepCopy()
 }
 
-// Interpolater returns an Interpolater built on a copy of the state
-// that can be used to test interpolation values.
-func (c *Context) Interpolater() *Interpolater {
-	var varLock sync.Mutex
-	var stateLock sync.RWMutex
-	return &Interpolater{
+// Evaluator returns an Evaluator that references this context's state, and
+// that can be used to obtain data for expression evaluation within the
+// receiving context.
+func (c *Context) Evaluator() *Evaluator {
+	return &Evaluator{
 		Operation:          walkApply,
 		Meta:               c.meta,
-		Module:             c.module,
-		State:              c.state.DeepCopy(),
-		StateLock:          &stateLock,
-		VariableValues:     c.variables,
-		VariableValuesLock: &varLock,
+		Config:             c.config,
+		State:              c.state,
+		StateLock:          &c.stateLock,
+		RootVariableValues: c.variables,
 	}
 }
 
+// Interpolater is no longer used. Use Evaluator instead.
+//
+// The interpolator returned from this function will return an error on any use.
+func (c *Context) Interpolater() *Interpolater {
+	// FIXME: Remove this once all callers are updated to no longer use it.
+	return &Interpolater{}
+}
+
 // Input asks for input to fill variables and provider configurations.
 // This modifies the configuration in-place, so asking for Input twice
 // may result in different UI output showing different current values.
-func (c *Context) Input(mode InputMode) error {
+func (c *Context) Input(mode InputMode) tfdiags.Diagnostics {
+	var diags tfdiags.Diagnostics
 	defer c.acquireRun("input")()
 
 	if mode&InputModeVar != 0 {
 		// Walk the variables first for the root module. We walk them in
 		// alphabetical order for UX reasons.
-		rootConf := c.module.Config()
-		names := make([]string, len(rootConf.Variables))
-		m := make(map[string]*config.Variable)
-		for i, v := range rootConf.Variables {
-			names[i] = v.Name
-			m[v.Name] = v
+		configs := c.config.Module.Variables
+		names := make([]string, 0, len(configs))
+		for name := range configs {
+			names = append(names, name)
 		}
 		sort.Strings(names)
+	Variables:
 		for _, n := range names {
-			// If we only care about unset variables, then if the variable
-			// is set, continue on.
+			v := configs[n]
+
+			// If we only care about unset variables, then we should set any
+			// variable that is already set.
 			if mode&InputModeVarUnset != 0 {
-				if _, ok := c.variables[n]; ok {
-					continue
-				}
-			}
-
-			var valueType config.VariableType
-
-			v := m[n]
-			switch valueType = v.Type(); valueType {
-			case config.VariableTypeUnknown:
-				continue
-			case config.VariableTypeMap:
-				// OK
-			case config.VariableTypeList:
-				// OK
-			case config.VariableTypeString:
-				// OK
-			default:
-				panic(fmt.Sprintf("Unknown variable type: %#v", v.Type()))
-			}
-
-			// If the variable is not already set, and the variable defines a
-			// default, use that for the value.
-			if _, ok := c.variables[n]; !ok {
-				if v.Default != nil {
-					c.variables[n] = v.Default.(string)
+				if _, isSet := c.variables[n]; isSet {
 					continue
 				}
 			}
 
 			// this should only happen during tests
 			if c.uiInput == nil {
-				log.Println("[WARN] Content.uiInput is nil")
+				log.Println("[WARN] Context.uiInput is nil during input walk")
 				continue
 			}
 
 			// Ask the user for a value for this variable
-			var value string
+			var rawValue string
 			retry := 0
 			for {
 				var err error
-				value, err = c.uiInput.Input(&InputOpts{
+				rawValue, err = c.uiInput.Input(&InputOpts{
 					Id:          fmt.Sprintf("var.%s", n),
 					Query:       fmt.Sprintf("var.%s", n),
 					Description: v.Description,
 				})
 				if err != nil {
-					return fmt.Errorf(
-						"Error asking for %s: %s", n, err)
+					diags = diags.Append(tfdiags.Sourceless(
+						tfdiags.Error,
+						"Failed to request interactive input",
+						fmt.Sprintf("Terraform attempted to request a value for var.%s interactively, but encountered an error: %s.", n, err),
+					))
+					return diags
 				}
 
-				if value == "" && v.Required() {
+				if rawValue == "" && v.Default == cty.NilVal {
 					// Redo if it is required, but abort if we keep getting
 					// blank entries
 					if retry > 2 {
-						return fmt.Errorf("missing required value for %q", n)
+						diags = diags.Append(tfdiags.Sourceless(
+							tfdiags.Error,
+							"Required variable not assigned",
+							fmt.Sprintf("The variable %q is required, so Terraform cannot proceed without a defined value for it.", n),
+						))
+						continue Variables
 					}
 					retry++
 					continue
@@ -438,18 +439,15 @@ func (c *Context) Input(mode InputMode) error {
 				break
 			}
 
-			// no value provided, so don't set the variable at all
-			if value == "" {
+			val, valDiags := v.ParsingMode.Parse(n, rawValue)
+			diags = diags.Append(valDiags)
+			if diags.HasErrors() {
 				continue
 			}
 
-			decoded, err := parseVariableAsHCL(n, value, valueType)
-			if err != nil {
-				return err
-			}
-
-			if decoded != nil {
-				c.variables[n] = decoded
+			c.variables[n] = &InputValue{
+				Value:      val,
+				SourceType: ValueFromInput,
 			}
 		}
 	}
@@ -458,16 +456,18 @@ func (c *Context) Input(mode InputMode) error {
 		// Build the graph
 		graph, err := c.Graph(GraphTypeInput, nil)
 		if err != nil {
-			return err
+			diags = diags.Append(err)
+			return diags
 		}
 
 		// Do the walk
 		if _, err := c.walk(graph, walkInput); err != nil {
-			return err
+			diags = diags.Append(err)
+			return diags
 		}
 	}
 
-	return nil
+	return diags
 }
 
 // Apply applies the changes represented by this context and returns
@@ -484,23 +484,16 @@ func (c *Context) Input(mode InputMode) error {
 //       State() method. Currently the helper/resource testing framework relies
 //       on the absence of a returned state to determine if Destroy can be
 //       called, so that will need to be refactored before this can be changed.
-func (c *Context) Apply() (*State, error) {
+func (c *Context) Apply() (*State, tfdiags.Diagnostics) {
 	defer c.acquireRun("apply")()
 
-	// Check there are no empty target parameter values
-	for _, target := range c.targets {
-		if target == "" {
-			return nil, fmt.Errorf("Target parameter must not have empty value")
-		}
-	}
-
 	// Copy our own state
 	c.state = c.state.DeepCopy()
 
 	// Build the graph.
-	graph, err := c.Graph(GraphTypeApply, nil)
-	if err != nil {
-		return nil, err
+	graph, diags := c.Graph(GraphTypeApply, nil)
+	if diags.HasErrors() {
+		return nil, diags
 	}
 
 	// Determine the operation
@@ -510,15 +503,14 @@ func (c *Context) Apply() (*State, error) {
 	}
 
 	// Walk the graph
-	walker, err := c.walk(graph, operation)
-	if len(walker.ValidationErrors) > 0 {
-		err = multierror.Append(err, walker.ValidationErrors...)
-	}
+	walker, walkDiags := c.walk(graph, operation)
+	diags = diags.Append(walker.NonFatalDiagnostics)
+	diags = diags.Append(walkDiags)
 
 	// Clean out any unused things
 	c.state.prune()
 
-	return c.state, err
+	return c.state, diags
 }
 
 // Plan generates an execution plan for the given context.
@@ -528,21 +520,22 @@ func (c *Context) Apply() (*State, error) {
 //
 // Plan also updates the diff of this context to be the diff generated
 // by the plan, so Apply can be called after.
-func (c *Context) Plan() (*Plan, error) {
+func (c *Context) Plan() (*Plan, tfdiags.Diagnostics) {
 	defer c.acquireRun("plan")()
 
-	// Check there are no empty target parameter values
-	for _, target := range c.targets {
-		if target == "" {
-			return nil, fmt.Errorf("Target parameter must not have empty value")
-		}
+	// The Plan struct wants the legacy-style of targets as a simple []string,
+	// so we must shim that here.
+	legacyTargets := make([]string, len(c.targets))
+	for i, addr := range c.targets {
+		legacyTargets[i] = addr.String()
 	}
 
+	var diags tfdiags.Diagnostics
 	p := &Plan{
-		Module:  c.module,
-		Vars:    c.variables,
+		Config:  c.config,
+		Vars:    c.variables.JustValues(),
 		State:   c.state,
-		Targets: c.targets,
+		Targets: legacyTargets,
 
 		TerraformVersion: version.String(),
 		ProviderSHA256s:  c.providerSHA256s,
@@ -581,15 +574,18 @@ func (c *Context) Plan() (*Plan, error) {
 	if c.destroy {
 		graphType = GraphTypePlanDestroy
 	}
-	graph, err := c.Graph(graphType, nil)
-	if err != nil {
-		return nil, err
+	graph, graphDiags := c.Graph(graphType, nil)
+	diags = diags.Append(graphDiags)
+	if graphDiags.HasErrors() {
+		return nil, diags
 	}
 
 	// Do the walk
-	walker, err := c.walk(graph, operation)
-	if err != nil {
-		return nil, err
+	walker, walkDiags := c.walk(graph, operation)
+	diags = diags.Append(walker.NonFatalDiagnostics)
+	diags = diags.Append(walkDiags)
+	if walkDiags.HasErrors() {
+		return nil, diags
 	}
 	p.Diff = c.diff
 
@@ -604,23 +600,7 @@ func (c *Context) Plan() (*Plan, error) {
 		p.Diff.DeepCopy()
 	}
 
-	/*
-		// We don't do the reverification during the new destroy plan because
-		// it will use a different apply process.
-		if X_legacyGraph {
-			// Now that we have a diff, we can build the exact graph that Apply will use
-			// and catch any possible cycles during the Plan phase.
-			if _, err := c.Graph(GraphTypeLegacy, nil); err != nil {
-				return nil, err
-			}
-		}
-	*/
-
-	var errs error
-	if len(walker.ValidationErrors) > 0 {
-		errs = multierror.Append(errs, walker.ValidationErrors...)
-	}
-	return p, errs
+	return p, diags
 }
 
 // Refresh goes through all the resources in the state and refreshes them
@@ -629,27 +609,29 @@ func (c *Context) Plan() (*Plan, error) {
 //
 // Even in the case an error is returned, the state may be returned and
 // will potentially be partially updated.
-func (c *Context) Refresh() (*State, error) {
+func (c *Context) Refresh() (*State, tfdiags.Diagnostics) {
 	defer c.acquireRun("refresh")()
 
 	// Copy our own state
 	c.state = c.state.DeepCopy()
 
 	// Build the graph.
-	graph, err := c.Graph(GraphTypeRefresh, nil)
-	if err != nil {
-		return nil, err
+	graph, diags := c.Graph(GraphTypeRefresh, nil)
+	if diags.HasErrors() {
+		return nil, diags
 	}
 
 	// Do the walk
-	if _, err := c.walk(graph, walkRefresh); err != nil {
-		return nil, err
+	_, walkDiags := c.walk(graph, walkRefresh)
+	diags = diags.Append(walkDiags)
+	if walkDiags.HasErrors() {
+		return nil, diags
 	}
 
 	// Clean out any unused things
 	c.state.prune()
 
-	return c.state, nil
+	return c.state, diags
 }
 
 // Stop stops the running task.
@@ -681,26 +663,26 @@ func (c *Context) Stop() {
 	log.Printf("[WARN] terraform: stop complete")
 }
 
-// Validate validates the configuration and returns any warnings or errors.
+// Validate performs semantic validation of the configuration, and returning
+// any warnings or errors.
+//
+// Syntax and structural checks are performed by the configuration loader,
+// and so are not repeated here.
 func (c *Context) Validate() tfdiags.Diagnostics {
 	defer c.acquireRun("validate")()
 
 	var diags tfdiags.Diagnostics
 
-	// Validate the configuration itself
-	diags = diags.Append(c.module.Validate())
-
-	// This only needs to be done for the root module, since inter-module
-	// variables are validated in the module tree.
-	if config := c.module.Config(); config != nil {
-		// Validate the user variables
-		for _, err := range smcUserVariables(config, c.variables) {
-			diags = diags.Append(err)
-		}
+	// Validate input variables. We do this only for the values supplied
+	// by the root module, since child module calls are validated when we
+	// visit their graph nodes.
+	if c.config != nil {
+		varDiags := checkInputVariables(c.config.Module.Variables, c.variables)
+		diags = diags.Append(varDiags)
 	}
 
-	// If we have errors at this point, the graphing has no chance,
-	// so just bail early.
+	// If we have errors at this point then we probably won't be able to
+	// construct a graph without producing redundant errors, so we'll halt early.
 	if diags.HasErrors() {
 		return diags
 	}
@@ -709,48 +691,41 @@ func (c *Context) Validate() tfdiags.Diagnostics {
 	// We also validate the graph generated here, but this graph doesn't
 	// necessarily match the graph that Plan will generate, so we'll validate the
 	// graph again later after Planning.
-	graph, err := c.Graph(GraphTypeValidate, nil)
-	if err != nil {
-		diags = diags.Append(err)
+	graph, graphDiags := c.Graph(GraphTypeValidate, nil)
+	diags = diags.Append(graphDiags)
+	if graphDiags.HasErrors() {
 		return diags
 	}
 
 	// Walk
-	walker, err := c.walk(graph, walkValidate)
-	if err != nil {
-		diags = diags.Append(err)
-	}
-
-	sort.Strings(walker.ValidationWarnings)
-	sort.Slice(walker.ValidationErrors, func(i, j int) bool {
-		return walker.ValidationErrors[i].Error() < walker.ValidationErrors[j].Error()
-	})
-
-	for _, warn := range walker.ValidationWarnings {
-		diags = diags.Append(tfdiags.SimpleWarning(warn))
-	}
-	for _, err := range walker.ValidationErrors {
-		diags = diags.Append(err)
+	walker, walkDiags := c.walk(graph, walkValidate)
+	diags = diags.Append(walker.NonFatalDiagnostics)
+	diags = diags.Append(walkDiags)
+	if walkDiags.HasErrors() {
+		return diags
 	}
 
 	return diags
 }
 
-// Module returns the module tree associated with this context.
-func (c *Context) Module() *module.Tree {
-	return c.module
+// Config returns the configuration tree associated with this context.
+func (c *Context) Config() *configs.Config {
+	return c.config
 }
 
 // Variables will return the mapping of variables that were defined
 // for this Context. If Input was called, this mapping may be different
 // than what was given.
-func (c *Context) Variables() map[string]interface{} {
+func (c *Context) Variables() InputValues {
 	return c.variables
 }
 
 // SetVariable sets a variable after a context has already been built.
-func (c *Context) SetVariable(k string, v interface{}) {
-	c.variables[k] = v
+func (c *Context) SetVariable(k string, v cty.Value) {
+	c.variables[k] = &InputValue{
+		Value:      v,
+		SourceType: ValueFromCaller,
+	}
 }
 
 func (c *Context) acquireRun(phase string) func() {
@@ -807,7 +782,7 @@ func (c *Context) releaseRun() {
 	c.runContext = nil
 }
 
-func (c *Context) walk(graph *Graph, operation walkOperation) (*ContextGraphWalker, error) {
+func (c *Context) walk(graph *Graph, operation walkOperation) (*ContextGraphWalker, tfdiags.Diagnostics) {
 	// Keep track of the "real" context which is the context that does
 	// the real work: talking to real providers, modifying real state, etc.
 	realCtx := c
@@ -824,13 +799,13 @@ func (c *Context) walk(graph *Graph, operation walkOperation) (*ContextGraphWalk
 	watchStop, watchWait := c.watchStop(walker)
 
 	// Walk the real graph, this will block until it completes
-	realErr := graph.Walk(walker)
+	diags := graph.Walk(walker)
 
 	// Close the channel so the watcher stops, and wait for it to return.
 	close(watchStop)
 	<-watchWait
 
-	return walker, realErr
+	return walker, diags
 }
 
 // watchStop immediately returns a `stop` and a `wait` chan after dispatching

terraform/context_import.go

@@ -1,7 +1,9 @@
 package terraform
 
 import (
-	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // ImportOpts are used as the configuration for Import.
@@ -9,23 +11,23 @@ type ImportOpts struct {
 	// Targets are the targets to import
 	Targets []*ImportTarget
 
-	// Module is optional, and specifies a config module that is loaded
-	// into the graph and evaluated. The use case for this is to provide
-	// provider configuration.
-	Module *module.Tree
+	// Config is optional, and specifies a config tree that will be loaded
+	// into the graph and evaluated. This is the source for provider
+	// configurations.
+	Config *configs.Config
 }
 
 // ImportTarget is a single resource to import.
 type ImportTarget struct {
-	// Addr is the full resource address of the resource to import.
-	// Example: "module.foo.aws_instance.bar"
-	Addr string
+	// Addr is the address for the resource instance that the new object should
+	// be imported into.
+	Addr addrs.AbsResourceInstance
 
 	// ID is the ID of the resource to import. This is resource-specific.
 	ID string
 
-	// Provider string
-	Provider string
+	// ProviderAddr is the address of the provider that should handle the import.
+	ProviderAddr addrs.AbsProviderConfig
 }
 
 // Import takes already-created external resources and brings them
@@ -38,7 +40,9 @@ type ImportTarget struct {
 // Further, this operation also gracefully handles partial state. If during
 // an import there is a failure, all previously imported resources remain
 // imported.
-func (c *Context) Import(opts *ImportOpts) (*State, error) {
+func (c *Context) Import(opts *ImportOpts) (*State, tfdiags.Diagnostics) {
+	var diags tfdiags.Diagnostics
+
 	// Hold a lock since we can modify our own state here
 	defer c.acquireRun("import")()
 
@@ -47,31 +51,34 @@ func (c *Context) Import(opts *ImportOpts) (*State, error) {
 
 	// If no module is given, default to the module configured with
 	// the Context.
-	module := opts.Module
-	if module == nil {
-		module = c.module
+	config := opts.Config
+	if config == nil {
+		config = c.config
 	}
 
 	// Initialize our graph builder
 	builder := &ImportGraphBuilder{
 		ImportTargets: opts.Targets,
-		Module:        module,
+		Config:        config,
 		Providers:     c.components.ResourceProviders(),
 	}
 
 	// Build the graph!
-	graph, err := builder.Build(RootModulePath)
-	if err != nil {
-		return c.state, err
+	graph, graphDiags := builder.Build(addrs.RootModuleInstance)
+	diags = diags.Append(graphDiags)
+	if graphDiags.HasErrors() {
+		return c.state, diags
 	}
 
 	// Walk it
-	if _, err := c.walk(graph, walkImport); err != nil {
-		return c.state, err
+	_, walkDiags := c.walk(graph, walkImport)
+	diags = diags.Append(walkDiags)
+	if walkDiags.HasErrors() {
+		return c.state, diags
 	}
 
 	// Clean the state
 	c.state.prune()
 
-	return c.state, nil
+	return c.state, diags
 }

terraform/diff.go

@@ -10,6 +10,8 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/hashicorp/terraform/addrs"
+
 	"github.com/mitchellh/copystructure"
 )
 
@@ -69,8 +71,24 @@ func (d *Diff) Prune() {
 //
 // This should be the preferred method to add module diffs since it
 // allows us to optimize lookups later as well as control sorting.
-func (d *Diff) AddModule(path []string) *ModuleDiff {
-	m := &ModuleDiff{Path: path}
+func (d *Diff) AddModule(path addrs.ModuleInstance) *ModuleDiff {
+	// Lower the new-style address into a legacy-style address.
+	// This requires that none of the steps have instance keys, which is
+	// true for all addresses at the time of implementing this because
+	// "count" and "for_each" are not yet implemented for modules.
+	legacyPath := make([]string, len(path))
+	for i, step := range path {
+		if step.InstanceKey != addrs.NoKey {
+			// FIXME: Once the rest of Terraform is ready to use count and
+			// for_each, remove all of this and just write the addrs.ModuleInstance
+			// value itself into the ModuleState.
+			panic("diff cannot represent modules with count or for_each keys")
+		}
+
+		legacyPath[i] = step.Name
+	}
+
+	m := &ModuleDiff{Path: legacyPath}
 	m.init()
 	d.Modules = append(d.Modules, m)
 	return m
@@ -79,7 +97,7 @@ func (d *Diff) AddModule(path []string) *ModuleDiff {
 // ModuleByPath is used to lookup the module diff for the given path.
 // This should be the preferred lookup mechanism as it allows for future
 // lookup optimizations.
-func (d *Diff) ModuleByPath(path []string) *ModuleDiff {
+func (d *Diff) ModuleByPath(path addrs.ModuleInstance) *ModuleDiff {
 	if d == nil {
 		return nil
 	}
@@ -87,7 +105,8 @@ func (d *Diff) ModuleByPath(path []string) *ModuleDiff {
 		if mod.Path == nil {
 			panic("missing module path")
 		}
-		if reflect.DeepEqual(mod.Path, path) {
+		modPath := normalizeModulePath(mod.Path)
+		if modPath.String() == path.String() {
 			return mod
 		}
 	}
@@ -96,7 +115,7 @@ func (d *Diff) ModuleByPath(path []string) *ModuleDiff {
 
 // RootModule returns the ModuleState for the root module
 func (d *Diff) RootModule() *ModuleDiff {
-	root := d.ModuleByPath(rootModulePath)
+	root := d.ModuleByPath(addrs.RootModuleInstance)
 	if root == nil {
 		panic("missing root module")
 	}

terraform/eval.go

@@ -2,7 +2,6 @@ package terraform
 
 import (
 	"log"
-	"strings"
 )
 
 // EvalNode is the interface that must be implemented by graph nodes to
@@ -46,7 +45,10 @@ func Eval(n EvalNode, ctx EvalContext) (interface{}, error) {
 func EvalRaw(n EvalNode, ctx EvalContext) (interface{}, error) {
 	path := "unknown"
 	if ctx != nil {
-		path = strings.Join(ctx.Path(), ".")
+		path = ctx.Path().String()
+	}
+	if path == "" {
+		path = "<root>"
 	}
 
 	log.Printf("[TRACE] %s: eval: %T", path, n)

terraform/eval_apply.go

@@ -3,16 +3,20 @@ package terraform
 import (
 	"fmt"
 	"log"
-	"strconv"
 
 	"github.com/hashicorp/go-multierror"
+	"github.com/zclconf/go-cty/cty/gocty"
+
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // EvalApply is an EvalNode implementation that writes the diff to
 // the full diff.
 type EvalApply struct {
-	Info      *InstanceInfo
+	Addr      addrs.ResourceInstance
 	State     **InstanceState
 	Diff      **InstanceDiff
 	Provider  *ResourceProvider
@@ -27,10 +31,11 @@ func (n *EvalApply) Eval(ctx EvalContext) (interface{}, error) {
 	provider := *n.Provider
 	state := *n.State
 
-	// If we have no diff, we have nothing to do!
+	// The provider API still expects our legacy InstanceInfo type, so we must shim it.
+	legacyInfo := NewInstanceInfo(n.Addr.Absolute(ctx.Path()).ContainingResource())
+
 	if diff.Empty() {
-		log.Printf(
-			"[DEBUG] apply: %s: diff is empty, doing nothing.", n.Info.Id)
+		log.Printf("[DEBUG] apply %s: diff is empty, so skipping.", n.Addr)
 		return nil, nil
 	}
 
@@ -53,8 +58,8 @@ func (n *EvalApply) Eval(ctx EvalContext) (interface{}, error) {
 	}
 
 	// With the completed diff, apply!
-	log.Printf("[DEBUG] apply: %s: executing Apply", n.Info.Id)
-	state, err := provider.Apply(n.Info, state, diff)
+	log.Printf("[DEBUG] apply %s: executing Apply", n.Addr)
+	state, err := provider.Apply(legacyInfo, state, diff)
 	if state == nil {
 		state = new(InstanceState)
 	}
@@ -84,7 +89,7 @@ func (n *EvalApply) Eval(ctx EvalContext) (interface{}, error) {
 	// if we have one, otherwise we just output it.
 	if err != nil {
 		if n.Error != nil {
-			helpfulErr := fmt.Errorf("%s: %s", n.Info.Id, err.Error())
+			helpfulErr := fmt.Errorf("%s: %s", n.Addr, err.Error())
 			*n.Error = multierror.Append(*n.Error, helpfulErr)
 		} else {
 			return nil, err
@@ -96,7 +101,7 @@ func (n *EvalApply) Eval(ctx EvalContext) (interface{}, error) {
 
 // EvalApplyPre is an EvalNode implementation that does the pre-Apply work
 type EvalApplyPre struct {
-	Info  *InstanceInfo
+	Addr  addrs.ResourceInstance
 	State **InstanceState
 	Diff  **InstanceDiff
 }
@@ -106,16 +111,20 @@ func (n *EvalApplyPre) Eval(ctx EvalContext) (interface{}, error) {
 	state := *n.State
 	diff := *n.Diff
 
+	// The hook API still uses our legacy InstanceInfo type, so we must
+	// shim it.
+	legacyInfo := NewInstanceInfo(n.Addr.ContainingResource().Absolute(ctx.Path()))
+
 	// If the state is nil, make it non-nil
 	if state == nil {
 		state = new(InstanceState)
 	}
 	state.init()
 
-	if resourceHasUserVisibleApply(n.Info) {
+	if resourceHasUserVisibleApply(legacyInfo) {
 		// Call post-apply hook
 		err := ctx.Hook(func(h Hook) (HookAction, error) {
-			return h.PreApply(n.Info, state, diff)
+			return h.PreApply(legacyInfo, state, diff)
 		})
 		if err != nil {
 			return nil, err
@@ -127,7 +136,7 @@ func (n *EvalApplyPre) Eval(ctx EvalContext) (interface{}, error) {
 
 // EvalApplyPost is an EvalNode implementation that does the post-Apply work
 type EvalApplyPost struct {
-	Info  *InstanceInfo
+	Addr  addrs.ResourceInstance
 	State **InstanceState
 	Error *error
 }
@@ -136,10 +145,14 @@ type EvalApplyPost struct {
 func (n *EvalApplyPost) Eval(ctx EvalContext) (interface{}, error) {
 	state := *n.State
 
-	if resourceHasUserVisibleApply(n.Info) {
+	// The hook API still uses our legacy InstanceInfo type, so we must
+	// shim it.
+	legacyInfo := NewInstanceInfo(n.Addr.ContainingResource().Absolute(ctx.Path()))
+
+	if resourceHasUserVisibleApply(legacyInfo) {
 		// Call post-apply hook
 		err := ctx.Hook(func(h Hook) (HookAction, error) {
-			return h.PostApply(n.Info, state, *n.Error)
+			return h.PostApply(legacyInfo, state, *n.Error)
 		})
 		if err != nil {
 			return nil, err
@@ -171,21 +184,23 @@ func resourceHasUserVisibleApply(info *InstanceInfo) bool {
 // TODO(mitchellh): This should probably be split up into a more fine-grained
 // ApplyProvisioner (single) that is looped over.
 type EvalApplyProvisioners struct {
-	Info           *InstanceInfo
+	Addr           addrs.ResourceInstance
 	State          **InstanceState
-	Resource       *config.Resource
-	InterpResource *Resource
+	ResourceConfig *configs.Resource
 	CreateNew      *bool
 	Error          *error
 
 	// When is the type of provisioner to run at this point
-	When config.ProvisionerWhen
+	When configs.ProvisionerWhen
 }
 
 // TODO: test
 func (n *EvalApplyProvisioners) Eval(ctx EvalContext) (interface{}, error) {
 	state := *n.State
 
+	// The hook API still uses the legacy InstanceInfo type, so we need to shim it.
+	legacyInfo := NewInstanceInfo(n.Addr.Resource.Absolute(ctx.Path()))
+
 	if n.CreateNew != nil && !*n.CreateNew {
 		// If we're not creating a new resource, then don't run provisioners
 		return nil, nil
@@ -198,7 +213,7 @@ func (n *EvalApplyProvisioners) Eval(ctx EvalContext) (interface{}, error) {
 	}
 
 	// taint tells us whether to enable tainting.
-	taint := n.When == config.ProvisionerWhenCreate
+	taint := n.When == configs.ProvisionerWhenCreate
 
 	if n.Error != nil && *n.Error != nil {
 		if taint {
@@ -212,7 +227,7 @@ func (n *EvalApplyProvisioners) Eval(ctx EvalContext) (interface{}, error) {
 	{
 		// Call pre hook
 		err := ctx.Hook(func(h Hook) (HookAction, error) {
-			return h.PreProvisionResource(n.Info, state)
+			return h.PreProvisionResource(legacyInfo, state)
 		})
 		if err != nil {
 			return nil, err
@@ -234,7 +249,7 @@ func (n *EvalApplyProvisioners) Eval(ctx EvalContext) (interface{}, error) {
 	{
 		// Call post hook
 		err := ctx.Hook(func(h Hook) (HookAction, error) {
-			return h.PostProvisionResource(n.Info, state)
+			return h.PostProvisionResource(legacyInfo, state)
 		})
 		if err != nil {
 			return nil, err
@@ -246,18 +261,18 @@ func (n *EvalApplyProvisioners) Eval(ctx EvalContext) (interface{}, error) {
 
 // filterProvisioners filters the provisioners on the resource to only
 // the provisioners specified by the "when" option.
-func (n *EvalApplyProvisioners) filterProvisioners() []*config.Provisioner {
+func (n *EvalApplyProvisioners) filterProvisioners() []*configs.Provisioner {
 	// Fast path the zero case
-	if n.Resource == nil {
+	if n.ResourceConfig == nil || n.ResourceConfig.Managed == nil {
 		return nil
 	}
 
-	if len(n.Resource.Provisioners) == 0 {
+	if len(n.ResourceConfig.Managed.Provisioners) == 0 {
 		return nil
 	}
 
-	result := make([]*config.Provisioner, 0, len(n.Resource.Provisioners))
-	for _, p := range n.Resource.Provisioners {
+	result := make([]*configs.Provisioner, 0, len(n.ResourceConfig.Managed.Provisioners))
+	for _, p := range n.ResourceConfig.Managed.Provisioners {
 		if p.When == n.When {
 			result = append(result, p)
 		}
@@ -266,64 +281,68 @@ func (n *EvalApplyProvisioners) filterProvisioners() []*config.Provisioner {
 	return result
 }
 
-func (n *EvalApplyProvisioners) apply(ctx EvalContext, provs []*config.Provisioner) error {
+func (n *EvalApplyProvisioners) apply(ctx EvalContext, provs []*configs.Provisioner) error {
+	instanceAddr := n.Addr
 	state := *n.State
 
+	// The hook API still uses the legacy InstanceInfo type, so we need to shim it.
+	legacyInfo := NewInstanceInfo(n.Addr.Resource.Absolute(ctx.Path()))
+
 	// Store the original connection info, restore later
 	origConnInfo := state.Ephemeral.ConnInfo
 	defer func() {
 		state.Ephemeral.ConnInfo = origConnInfo
 	}()
 
+	var diags tfdiags.Diagnostics
+
 	for _, prov := range provs {
 		// Get the provisioner
 		provisioner := ctx.Provisioner(prov.Type)
+		schema := ctx.ProvisionerSchema(prov.Type)
 
-		// Interpolate the provisioner config
-		provConfig, err := ctx.Interpolate(prov.RawConfig.Copy(), n.InterpResource)
-		if err != nil {
-			return err
+		// Evaluate the main provisioner configuration.
+		config, _, configDiags := ctx.EvaluateBlock(prov.Config, schema, instanceAddr)
+		diags = diags.Append(configDiags)
+
+		connInfo, _, connInfoDiags := ctx.EvaluateBlock(prov.Config, connectionBlockSupersetSchema, instanceAddr)
+		diags = diags.Append(connInfoDiags)
+
+		if configDiags.HasErrors() || connInfoDiags.HasErrors() {
+			continue
 		}
 
-		// Interpolate the conn info, since it may contain variables
-		connInfo, err := ctx.Interpolate(prov.ConnInfo.Copy(), n.InterpResource)
-		if err != nil {
-			return err
-		}
-
-		// Merge the connection information
+		// Merge the connection information, and also lower everything to strings
+		// for compatibility with the communicator API.
 		overlay := make(map[string]string)
 		if origConnInfo != nil {
 			for k, v := range origConnInfo {
 				overlay[k] = v
 			}
 		}
-		for k, v := range connInfo.Config {
-			switch vt := v.(type) {
-			case string:
-				overlay[k] = vt
-			case int64:
-				overlay[k] = strconv.FormatInt(vt, 10)
-			case int32:
-				overlay[k] = strconv.FormatInt(int64(vt), 10)
-			case int:
-				overlay[k] = strconv.FormatInt(int64(vt), 10)
-			case float32:
-				overlay[k] = strconv.FormatFloat(float64(vt), 'f', 3, 32)
-			case float64:
-				overlay[k] = strconv.FormatFloat(vt, 'f', 3, 64)
-			case bool:
-				overlay[k] = strconv.FormatBool(vt)
-			default:
-				overlay[k] = fmt.Sprintf("%v", vt)
+		for it := connInfo.ElementIterator(); it.Next(); {
+			kv, vv := it.Element()
+			var k, v string
+
+			err := gocty.FromCtyValue(kv, &k)
+			if err != nil {
+				// Should never happen, because connectionBlockSupersetSchema requires all primitives
+				panic(err)
 			}
+			err = gocty.FromCtyValue(vv, &v)
+			if err != nil {
+				// Should never happen, because connectionBlockSupersetSchema requires all primitives
+				panic(err)
+			}
+
+			overlay[k] = v
 		}
 		state.Ephemeral.ConnInfo = overlay
 
 		{
 			// Call pre hook
 			err := ctx.Hook(func(h Hook) (HookAction, error) {
-				return h.PreProvision(n.Info, prov.Type)
+				return h.PreProvision(legacyInfo, prov.Type)
 			})
 			if err != nil {
 				return err
@@ -333,30 +352,31 @@ func (n *EvalApplyProvisioners) apply(ctx EvalContext, provs []*config.Provision
 		// The output function
 		outputFn := func(msg string) {
 			ctx.Hook(func(h Hook) (HookAction, error) {
-				h.ProvisionOutput(n.Info, prov.Type, msg)
+				h.ProvisionOutput(legacyInfo, prov.Type, msg)
 				return HookActionContinue, nil
 			})
 		}
 
+		// The provisioner API still uses our legacy ResourceConfig type, so
+		// we need to shim it.
+		legacyRC := NewResourceConfigShimmed(config, schema)
+
 		// Invoke the Provisioner
 		output := CallbackUIOutput{OutputFn: outputFn}
-		applyErr := provisioner.Apply(&output, state, provConfig)
+		applyErr := provisioner.Apply(&output, state, legacyRC)
 
 		// Call post hook
 		hookErr := ctx.Hook(func(h Hook) (HookAction, error) {
-			return h.PostProvision(n.Info, prov.Type, applyErr)
+			return h.PostProvision(legacyInfo, prov.Type, applyErr)
 		})
 
 		// Handle the error before we deal with the hook
 		if applyErr != nil {
 			// Determine failure behavior
 			switch prov.OnFailure {
-			case config.ProvisionerOnFailureContinue:
-				log.Printf(
-					"[INFO] apply: %s [%s]: error during provision, continue requested",
-					n.Info.Id, prov.Type)
-
-			case config.ProvisionerOnFailureFail:
+			case configs.ProvisionerOnFailureContinue:
+				log.Printf("[INFO] apply %s [%s]: error during provision, but continuing as requested in configuration", n.Addr, prov.Type)
+			case configs.ProvisionerOnFailureFail:
 				return applyErr
 			}
 		}
@@ -367,6 +387,5 @@ func (n *EvalApplyProvisioners) apply(ctx EvalContext, provs []*config.Provision
 		}
 	}
 
-	return nil
-
+	return diags.ErrWithWarnings()
 }

terraform/eval_check_prevent_destroy.go

@@ -3,33 +3,42 @@ package terraform
 import (
 	"fmt"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/hcl2/hcl"
+
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // EvalPreventDestroy is an EvalNode implementation that returns an
 // error if a resource has PreventDestroy configured and the diff
 // would destroy the resource.
 type EvalCheckPreventDestroy struct {
-	Resource   *config.Resource
-	ResourceId string
-	Diff       **InstanceDiff
+	Addr   addrs.ResourceInstance
+	Config *configs.Resource
+	Diff   **InstanceDiff
 }
 
 func (n *EvalCheckPreventDestroy) Eval(ctx EvalContext) (interface{}, error) {
-	if n.Diff == nil || *n.Diff == nil || n.Resource == nil {
+	if n.Diff == nil || *n.Diff == nil || n.Config == nil || n.Config.Managed == nil {
 		return nil, nil
 	}
 
 	diff := *n.Diff
-	preventDestroy := n.Resource.Lifecycle.PreventDestroy
+	preventDestroy := n.Config.Managed.PreventDestroy
 
 	if diff.GetDestroy() && preventDestroy {
-		resourceId := n.ResourceId
-		if resourceId == "" {
-			resourceId = n.Resource.Id()
-		}
-
-		return nil, fmt.Errorf(preventDestroyErrStr, resourceId)
+		var diags tfdiags.Diagnostics
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Instance cannot be destroyed",
+			Detail: fmt.Sprintf(
+				"Resource %s has lifecycle.prevent_destroy set, but the plan calls for this resource to be destroyed. To avoid this error and continue with the plan, either disable lifecycle.prevent_destroy or reduce the scope of the plan using the -target flag.",
+				n.Addr.Absolute(ctx.Path()).String(),
+			),
+			Subject: &n.Config.DeclRange,
+		})
+		return nil, diags.Err()
 	}
 
 	return nil, nil

terraform/eval_context.go

@@ -3,7 +3,11 @@ package terraform
 import (
 	"sync"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/config/configschema"
+	"github.com/hashicorp/terraform/tfdiags"
+	"github.com/zclconf/go-cty/cty"
 )
 
 // EvalContext is the interface that is given to eval nodes to execute.
@@ -13,7 +17,7 @@ type EvalContext interface {
 	Stopped() <-chan struct{}
 
 	// Path is the current module path.
-	Path() []string
+	Path() addrs.ModuleInstance
 
 	// Hook is used to call hook methods. The callback is called for each
 	// hook and should return the hook action to take and the error.
@@ -22,33 +26,41 @@ type EvalContext interface {
 	// Input is the UIInput object for interacting with the UI.
 	Input() UIInput
 
-	// InitProvider initializes the provider with the given type and name, and
+	// InitProvider initializes the provider with the given type and address, and
 	// returns the implementation of the resource provider or an error.
 	//
 	// It is an error to initialize the same provider more than once.
-	InitProvider(typ string, name string) (ResourceProvider, error)
+	InitProvider(typ string, addr addrs.ProviderConfig) (ResourceProvider, error)
 
-	// Provider gets the provider instance with the given name (already
+	// Provider gets the provider instance with the given address (already
 	// initialized) or returns nil if the provider isn't initialized.
-	Provider(string) ResourceProvider
+	//
+	// This method expects an _absolute_ provider configuration address, since
+	// resources in one module are able to use providers from other modules.
+	// InitProvider must've been called on the EvalContext of the module
+	// that owns the given provider before calling this method.
+	Provider(addrs.AbsProviderConfig) ResourceProvider
 
 	// ProviderSchema retrieves the schema for a particular provider, which
-	// must have already be initialized with InitProvider.
-	ProviderSchema(string) *ProviderSchema
+	// must have already been initialized with InitProvider.
+	//
+	// This method expects an _absolute_ provider configuration address, since
+	// resources in one module are able to use providers from other modules.
+	ProviderSchema(addrs.AbsProviderConfig) *ProviderSchema
 
 	// CloseProvider closes provider connections that aren't needed anymore.
-	CloseProvider(string) error
+	CloseProvider(addrs.ProviderConfig) error
 
 	// ConfigureProvider configures the provider with the given
 	// configuration. This is a separate context call because this call
 	// is used to store the provider configuration for inheritance lookups
 	// with ParentProviderConfig().
-	ConfigureProvider(string, *ResourceConfig) error
+	ConfigureProvider(addrs.ProviderConfig, cty.Value) tfdiags.Diagnostics
 
 	// ProviderInput and SetProviderInput are used to configure providers
 	// from user input.
-	ProviderInput(string) map[string]interface{}
-	SetProviderInput(string, map[string]interface{})
+	ProviderInput(addrs.ProviderConfig) map[string]cty.Value
+	SetProviderInput(addrs.ProviderConfig, map[string]cty.Value)
 
 	// InitProvisioner initializes the provisioner with the given name and
 	// returns the implementation of the resource provisioner or an error.
@@ -60,28 +72,43 @@ type EvalContext interface {
 	// initialized) or returns nil if the provisioner isn't initialized.
 	Provisioner(string) ResourceProvisioner
 
+	// ProvisionerSchema retrieves the main configuration schema for a
+	// particular provisioner, which must have already been initialized with
+	// InitProvisioner.
+	ProvisionerSchema(string) *configschema.Block
+
 	// CloseProvisioner closes provisioner connections that aren't needed
 	// anymore.
 	CloseProvisioner(string) error
 
-	// Interpolate takes the given raw configuration and completes
-	// the interpolations, returning the processed ResourceConfig.
+	// EvaluateBlock takes the given raw configuration block and associated
+	// schema and evaluates it to produce a value of an object type that
+	// conforms to the implied type of the schema.
 	//
-	// The resource argument is optional. If given, it is the resource
-	// that is currently being acted upon.
-	Interpolate(*config.RawConfig, *Resource) (*ResourceConfig, error)
+	// The "self" argument is optional. If given, it is the referenceable
+	// address that the name "self" should behave as an alias for when
+	// evaluating. Set this to nil if the "self" object should not be available.
+	//
+	// The returned body is an expanded version of the given body, with any
+	// "dynamic" blocks replaced with zero or more static blocks. This can be
+	// used to extract correct source location information about attributes of
+	// the returned object value.
+	EvaluateBlock(body hcl.Body, schema *configschema.Block, self addrs.Referenceable) (cty.Value, hcl.Body, tfdiags.Diagnostics)
 
-	// InterpolateProvider takes a ProviderConfig and interpolates it with the
-	// stored interpolation scope. Since provider configurations can be
-	// inherited, the interpolation scope may be different from the current
-	// context path. Interplation is otherwise executed the same as in the
-	// Interpolation method.
-	InterpolateProvider(*config.ProviderConfig, *Resource) (*ResourceConfig, error)
+	// EvaluateExpr takes the given HCL expression and evaluates it to produce
+	// a value.
+	//
+	// The "self" argument is optional. If given, it is the referenceable
+	// address that the name "self" should behave as an alias for when
+	// evaluating. Set this to nil if the "self" object should not be available.
+	EvaluateExpr(expr hcl.Expression, wantType cty.Type, self addrs.Referenceable) (cty.Value, tfdiags.Diagnostics)
 
-	// SetVariables sets the variables for the module within
-	// this context with the name n. This function call is additive:
-	// the second parameter is merged with any previous call.
-	SetVariables(string, map[string]interface{})
+	// SetModuleCallArguments defines values for the variables of a particular
+	// child module call.
+	//
+	// Calling this function multiple times has merging behavior, keeping any
+	// previously-set keys that are not present in the new map.
+	SetModuleCallArguments(addrs.ModuleCallInstance, map[string]cty.Value)
 
 	// Diff returns the global diff as well as the lock that should
 	// be used to modify that diff.

terraform/eval_context_builtin.go

@@ -6,7 +6,12 @@ import (
 	"log"
 	"sync"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/config/configschema"
+	"github.com/hashicorp/terraform/tfdiags"
+
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/zclconf/go-cty/cty"
 )
 
 // BuiltinEvalContext is an EvalContext implementation that is used by
@@ -16,27 +21,24 @@ type BuiltinEvalContext struct {
 	StopContext context.Context
 
 	// PathValue is the Path that this context is operating within.
-	PathValue []string
+	PathValue addrs.ModuleInstance
 
-	// Interpolater setting below affect the interpolation of variables.
-	//
-	// The InterpolaterVars are the exact value for ${var.foo} values.
-	// The map is shared between all contexts and is a mapping of
-	// PATH to KEY to VALUE. Because it is shared by all contexts as well
-	// as the Interpolater itself, it is protected by InterpolaterVarLock
-	// which must be locked during any access to the map.
-	Interpolater        *Interpolater
-	InterpolaterVars    map[string]map[string]interface{}
-	InterpolaterVarLock *sync.Mutex
+	// Evaluator is used for evaluating expressions within the scope of this
+	// eval context.
+	Evaluator *Evaluator
+
+	ChildModuleCallArgs  map[string]map[string]cty.Value
+	ChildModuleCallsLock *sync.Mutex
 
 	Components          contextComponentFactory
 	Hooks               []Hook
 	InputValue          UIInput
 	ProviderCache       map[string]ResourceProvider
 	ProviderSchemas     map[string]*ProviderSchema
-	ProviderInputConfig map[string]map[string]interface{}
+	ProviderInputConfig map[string]map[string]cty.Value
 	ProviderLock        *sync.Mutex
 	ProvisionerCache    map[string]ResourceProvisioner
+	ProvisionerSchemas  map[string]*configschema.Block
 	ProvisionerLock     *sync.Mutex
 	DiffValue           *Diff
 	DiffLock            *sync.RWMutex
@@ -46,6 +48,9 @@ type BuiltinEvalContext struct {
 	once sync.Once
 }
 
+// BuiltinEvalContext implements EvalContext
+var _ EvalContext = (*BuiltinEvalContext)(nil)
+
 func (ctx *BuiltinEvalContext) Stopped() <-chan struct{} {
 	// This can happen during tests. During tests, we just block forever.
 	if ctx.StopContext == nil {
@@ -79,12 +84,13 @@ func (ctx *BuiltinEvalContext) Input() UIInput {
 	return ctx.InputValue
 }
 
-func (ctx *BuiltinEvalContext) InitProvider(typeName, name string) (ResourceProvider, error) {
+func (ctx *BuiltinEvalContext) InitProvider(typeName string, addr addrs.ProviderConfig) (ResourceProvider, error) {
 	ctx.once.Do(ctx.init)
+	absAddr := addr.Absolute(ctx.Path())
 
 	// If we already initialized, it is an error
-	if p := ctx.Provider(name); p != nil {
-		return nil, fmt.Errorf("Provider '%s' already initialized", name)
+	if p := ctx.Provider(absAddr); p != nil {
+		return nil, fmt.Errorf("%s is already initialized", addr)
 	}
 
 	// Warning: make sure to acquire these locks AFTER the call to Provider
@@ -92,12 +98,14 @@ func (ctx *BuiltinEvalContext) InitProvider(typeName, name string) (ResourceProv
 	ctx.ProviderLock.Lock()
 	defer ctx.ProviderLock.Unlock()
 
-	p, err := ctx.Components.ResourceProvider(typeName, name)
+	key := addr.String()
+
+	p, err := ctx.Components.ResourceProvider(typeName, key)
 	if err != nil {
 		return nil, err
 	}
 
-	ctx.ProviderCache[name] = p
+	ctx.ProviderCache[key] = p
 
 	// Also fetch and cache the provider's schema.
 	// FIXME: This is using a non-ideal provider API that requires us to
@@ -120,45 +128,46 @@ func (ctx *BuiltinEvalContext) InitProvider(typeName, name string) (ResourceProv
 		ResourceTypes: resourceTypeNames,
 	})
 	if err != nil {
-		return nil, fmt.Errorf("error fetching schema for %s: %s", name, err)
+		return nil, fmt.Errorf("error fetching schema for %s: %s", key, err)
 	}
 	if ctx.ProviderSchemas == nil {
 		ctx.ProviderSchemas = make(map[string]*ProviderSchema)
 	}
-	ctx.ProviderSchemas[name] = schema
+	ctx.ProviderSchemas[key] = schema
 
 	return p, nil
 }
 
-func (ctx *BuiltinEvalContext) Provider(n string) ResourceProvider {
+func (ctx *BuiltinEvalContext) Provider(addr addrs.AbsProviderConfig) ResourceProvider {
 	ctx.once.Do(ctx.init)
 
 	ctx.ProviderLock.Lock()
 	defer ctx.ProviderLock.Unlock()
 
-	return ctx.ProviderCache[n]
+	return ctx.ProviderCache[addr.String()]
 }
 
-func (ctx *BuiltinEvalContext) ProviderSchema(n string) *ProviderSchema {
+func (ctx *BuiltinEvalContext) ProviderSchema(addr addrs.AbsProviderConfig) *ProviderSchema {
 	ctx.once.Do(ctx.init)
 
 	ctx.ProviderLock.Lock()
 	defer ctx.ProviderLock.Unlock()
 
-	return ctx.ProviderSchemas[n]
+	return ctx.ProviderSchemas[addr.String()]
 }
 
-func (ctx *BuiltinEvalContext) CloseProvider(n string) error {
+func (ctx *BuiltinEvalContext) CloseProvider(addr addrs.ProviderConfig) error {
 	ctx.once.Do(ctx.init)
 
 	ctx.ProviderLock.Lock()
 	defer ctx.ProviderLock.Unlock()
 
+	key := addr.String()
 	var provider interface{}
-	provider = ctx.ProviderCache[n]
+	provider = ctx.ProviderCache[key]
 	if provider != nil {
 		if p, ok := provider.(ResourceProviderCloser); ok {
-			delete(ctx.ProviderCache, n)
+			delete(ctx.ProviderCache, key)
 			return p.Close()
 		}
 	}
@@ -166,28 +175,32 @@ func (ctx *BuiltinEvalContext) CloseProvider(n string) error {
 	return nil
 }
 
-func (ctx *BuiltinEvalContext) ConfigureProvider(
-	n string, cfg *ResourceConfig) error {
-	p := ctx.Provider(n)
+func (ctx *BuiltinEvalContext) ConfigureProvider(addr addrs.ProviderConfig, cfg cty.Value) tfdiags.Diagnostics {
+	var diags tfdiags.Diagnostics
+	absAddr := addr.Absolute(ctx.Path())
+	p := ctx.Provider(absAddr)
 	if p == nil {
-		return fmt.Errorf("Provider '%s' not initialized", n)
+		diags = diags.Append(fmt.Errorf("%s not initialized", addr))
+		return diags
 	}
-	return p.Configure(cfg)
+	// FIXME: The provider API isn't yet updated to take a cty.Value directly.
+	rc := NewResourceConfigShimmed(cfg, ctx.ProviderSchema(absAddr).Provider)
+	err := p.Configure(rc)
+	if err != nil {
+		diags = diags.Append(err)
+	}
+	return diags
 }
 
-func (ctx *BuiltinEvalContext) ProviderInput(n string) map[string]interface{} {
+func (ctx *BuiltinEvalContext) ProviderInput(pc addrs.ProviderConfig) map[string]cty.Value {
 	ctx.ProviderLock.Lock()
 	defer ctx.ProviderLock.Unlock()
 
-	// Make a copy of the path so we can safely edit it
+	// Go up the module tree, looking for input results for the given provider
+	// configuration.
 	path := ctx.Path()
-	pathCopy := make([]string, len(path)+1)
-	copy(pathCopy, path)
-
-	// Go up the tree.
-	for i := len(path) - 1; i >= 0; i-- {
-		pathCopy[i+1] = n
-		k := PathCacheKey(pathCopy[:i+2])
+	for i := len(path); i >= 0; i-- {
+		k := pc.Absolute(path[:i]).String()
 		if v, ok := ctx.ProviderInputConfig[k]; ok {
 			return v
 		}
@@ -196,19 +209,16 @@ func (ctx *BuiltinEvalContext) ProviderInput(n string) map[string]interface{} {
 	return nil
 }
 
-func (ctx *BuiltinEvalContext) SetProviderInput(n string, c map[string]interface{}) {
-	providerPath := make([]string, len(ctx.Path())+1)
-	copy(providerPath, ctx.Path())
-	providerPath[len(providerPath)-1] = n
+func (ctx *BuiltinEvalContext) SetProviderInput(pc addrs.ProviderConfig, c map[string]cty.Value) {
+	absProvider := pc.Absolute(ctx.Path())
 
 	// Save the configuration
 	ctx.ProviderLock.Lock()
-	ctx.ProviderInputConfig[PathCacheKey(providerPath)] = c
+	ctx.ProviderInputConfig[absProvider.String()] = c
 	ctx.ProviderLock.Unlock()
 }
 
-func (ctx *BuiltinEvalContext) InitProvisioner(
-	n string) (ResourceProvisioner, error) {
+func (ctx *BuiltinEvalContext) InitProvisioner(n string) (ResourceProvisioner, error) {
 	ctx.once.Do(ctx.init)
 
 	// If we already initialized, it is an error
@@ -221,10 +231,7 @@ func (ctx *BuiltinEvalContext) InitProvisioner(
 	ctx.ProvisionerLock.Lock()
 	defer ctx.ProvisionerLock.Unlock()
 
-	provPath := make([]string, len(ctx.Path())+1)
-	copy(provPath, ctx.Path())
-	provPath[len(provPath)-1] = n
-	key := PathCacheKey(provPath)
+	key := PathObjectCacheKey(ctx.Path(), n)
 
 	p, err := ctx.Components.ResourceProvisioner(n, key)
 	if err != nil {
@@ -232,6 +239,17 @@ func (ctx *BuiltinEvalContext) InitProvisioner(
 	}
 
 	ctx.ProvisionerCache[key] = p
+
+	// Also fetch the provisioner's schema
+	schema, err := p.GetConfigSchema()
+	if err != nil {
+		return nil, fmt.Errorf("error getting schema for provisioner %q: %s", n, err)
+	}
+	if ctx.ProvisionerSchemas == nil {
+		ctx.ProvisionerSchemas = make(map[string]*configschema.Block)
+	}
+	ctx.ProvisionerSchemas[n] = schema
+
 	return p, nil
 }
 
@@ -241,11 +259,17 @@ func (ctx *BuiltinEvalContext) Provisioner(n string) ResourceProvisioner {
 	ctx.ProvisionerLock.Lock()
 	defer ctx.ProvisionerLock.Unlock()
 
-	provPath := make([]string, len(ctx.Path())+1)
-	copy(provPath, ctx.Path())
-	provPath[len(provPath)-1] = n
+	key := PathObjectCacheKey(ctx.Path(), n)
+	return ctx.ProvisionerCache[key]
+}
 
-	return ctx.ProvisionerCache[PathCacheKey(provPath)]
+func (ctx *BuiltinEvalContext) ProvisionerSchema(n string) *configschema.Block {
+	ctx.once.Do(ctx.init)
+
+	ctx.ProviderLock.Lock()
+	defer ctx.ProviderLock.Unlock()
+
+	return ctx.ProvisionerSchemas[n]
 }
 
 func (ctx *BuiltinEvalContext) CloseProvisioner(n string) error {
@@ -254,15 +278,13 @@ func (ctx *BuiltinEvalContext) CloseProvisioner(n string) error {
 	ctx.ProvisionerLock.Lock()
 	defer ctx.ProvisionerLock.Unlock()
 
-	provPath := make([]string, len(ctx.Path())+1)
-	copy(provPath, ctx.Path())
-	provPath[len(provPath)-1] = n
+	key := PathObjectCacheKey(ctx.Path(), n)
 
 	var prov interface{}
-	prov = ctx.ProvisionerCache[PathCacheKey(provPath)]
+	prov = ctx.ProvisionerCache[key]
 	if prov != nil {
 		if p, ok := prov.(ResourceProvisionerCloser); ok {
-			delete(ctx.ProvisionerCache, PathCacheKey(provPath))
+			delete(ctx.ProvisionerCache, key)
 			return p.Close()
 		}
 	}
@@ -270,81 +292,40 @@ func (ctx *BuiltinEvalContext) CloseProvisioner(n string) error {
 	return nil
 }
 
-func (ctx *BuiltinEvalContext) Interpolate(
-	cfg *config.RawConfig, r *Resource) (*ResourceConfig, error) {
-
-	if cfg != nil {
-		scope := &InterpolationScope{
-			Path:     ctx.Path(),
-			Resource: r,
-		}
-
-		vs, err := ctx.Interpolater.Values(scope, cfg.Variables)
-		if err != nil {
-			return nil, err
-		}
-
-		// Do the interpolation
-		if err := cfg.Interpolate(vs); err != nil {
-			return nil, err
-		}
-	}
-
-	result := NewResourceConfig(cfg)
-	result.interpolateForce()
-	return result, nil
+func (ctx *BuiltinEvalContext) EvaluateBlock(body hcl.Body, schema *configschema.Block, self addrs.Referenceable) (cty.Value, hcl.Body, tfdiags.Diagnostics) {
+	var diags tfdiags.Diagnostics
+	scope := ctx.Evaluator.Scope(ctx.PathValue, self)
+	body, evalDiags := scope.ExpandBlock(body, schema)
+	diags = diags.Append(evalDiags)
+	val, evalDiags := scope.EvalBlock(body, schema)
+	diags = diags.Append(evalDiags)
+	return val, body, diags
 }
 
-func (ctx *BuiltinEvalContext) InterpolateProvider(
-	pc *config.ProviderConfig, r *Resource) (*ResourceConfig, error) {
-
-	var cfg *config.RawConfig
-
-	if pc != nil && pc.RawConfig != nil {
-		scope := &InterpolationScope{
-			Path:     ctx.Path(),
-			Resource: r,
-		}
-
-		cfg = pc.RawConfig
-
-		vs, err := ctx.Interpolater.Values(scope, cfg.Variables)
-		if err != nil {
-			return nil, err
-		}
-
-		// Do the interpolation
-		if err := cfg.Interpolate(vs); err != nil {
-			return nil, err
-		}
-	}
-
-	result := NewResourceConfig(cfg)
-	result.interpolateForce()
-	return result, nil
+func (ctx *BuiltinEvalContext) EvaluateExpr(expr hcl.Expression, wantType cty.Type, self addrs.Referenceable) (cty.Value, tfdiags.Diagnostics) {
+	scope := ctx.Evaluator.Scope(ctx.PathValue, self)
+	return scope.EvalExpr(expr, wantType)
 }
 
-func (ctx *BuiltinEvalContext) Path() []string {
+func (ctx *BuiltinEvalContext) Path() addrs.ModuleInstance {
 	return ctx.PathValue
 }
 
-func (ctx *BuiltinEvalContext) SetVariables(n string, vs map[string]interface{}) {
-	ctx.InterpolaterVarLock.Lock()
-	defer ctx.InterpolaterVarLock.Unlock()
+func (ctx *BuiltinEvalContext) SetModuleCallArguments(n addrs.ModuleCallInstance, vals map[string]cty.Value) {
+	ctx.ChildModuleCallsLock.Lock()
+	defer ctx.ChildModuleCallsLock.Unlock()
 
-	path := make([]string, len(ctx.Path())+1)
-	copy(path, ctx.Path())
-	path[len(path)-1] = n
-	key := PathCacheKey(path)
+	childPath := ctx.Path().Child(n.Call.Name, n.Key)
+	key := childPath.String()
 
-	vars := ctx.InterpolaterVars[key]
-	if vars == nil {
-		vars = make(map[string]interface{})
-		ctx.InterpolaterVars[key] = vars
+	args := ctx.ChildModuleCallArgs[key]
+	if args == nil {
+		args = make(map[string]cty.Value)
+		ctx.ChildModuleCallArgs[key] = args
 	}
 
-	for k, v := range vs {
-		vars[k] = v
+	for k, v := range vals {
+		args[k] = v
 	}
 }
 

terraform/eval_context_mock.go

@@ -3,6 +3,13 @@ package terraform
 import (
 	"sync"
 
+	"github.com/hashicorp/terraform/addrs"
+
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/config/configschema"
+	"github.com/hashicorp/terraform/tfdiags"
+	"github.com/zclconf/go-cty/cty"
+
 	"github.com/hashicorp/terraform/config"
 )
 
@@ -20,34 +27,35 @@ type MockEvalContext struct {
 	InputInput  UIInput
 
 	InitProviderCalled   bool
-	InitProviderName     string
+	InitProviderType     string
+	InitProviderAddr     addrs.ProviderConfig
 	InitProviderProvider ResourceProvider
 	InitProviderError    error
 
 	ProviderCalled   bool
-	ProviderName     string
+	ProviderAddr     addrs.AbsProviderConfig
 	ProviderProvider ResourceProvider
 
 	ProviderSchemaCalled bool
-	ProviderSchemaName   string
+	ProviderSchemaAddr   addrs.AbsProviderConfig
 	ProviderSchemaSchema *ProviderSchema
 
 	CloseProviderCalled   bool
-	CloseProviderName     string
+	CloseProviderAddr     addrs.ProviderConfig
 	CloseProviderProvider ResourceProvider
 
 	ProviderInputCalled bool
-	ProviderInputName   string
-	ProviderInputConfig map[string]interface{}
+	ProviderInputAddr   addrs.ProviderConfig
+	ProviderInputValues map[string]cty.Value
 
 	SetProviderInputCalled bool
-	SetProviderInputName   string
-	SetProviderInputConfig map[string]interface{}
+	SetProviderInputAddr   addrs.ProviderConfig
+	SetProviderInputValues map[string]cty.Value
 
 	ConfigureProviderCalled bool
-	ConfigureProviderName   string
-	ConfigureProviderConfig *ResourceConfig
-	ConfigureProviderError  error
+	ConfigureProviderAddr   addrs.ProviderConfig
+	ConfigureProviderConfig cty.Value
+	ConfigureProviderDiags  tfdiags.Diagnostics
 
 	InitProvisionerCalled      bool
 	InitProvisionerName        string
@@ -58,10 +66,29 @@ type MockEvalContext struct {
 	ProvisionerName        string
 	ProvisionerProvisioner ResourceProvisioner
 
+	ProvisionerSchemaCalled bool
+	ProvisionerSchemaName   string
+	ProvisionerSchemaSchema *configschema.Block
+
 	CloseProvisionerCalled      bool
 	CloseProvisionerName        string
 	CloseProvisionerProvisioner ResourceProvisioner
 
+	EvaluateBlockCalled       bool
+	EvaluateBlockBody         hcl.Body
+	EvaluateBlockSchema       *configschema.Block
+	EvaluateBlockSelf         addrs.Referenceable
+	EvaluateBlockResult       cty.Value
+	EvaluateBlockExpandedBody hcl.Body
+	EvaluateBlockDiags        tfdiags.Diagnostics
+
+	EvaluateExprCalled   bool
+	EvaluateExprExpr     hcl.Expression
+	EvaluateExprWantType cty.Type
+	EvaluateExprSelf     addrs.Referenceable
+	EvaluateExprResult   cty.Value
+	EvaluateExprDiags    tfdiags.Diagnostics
+
 	InterpolateCalled       bool
 	InterpolateConfig       *config.RawConfig
 	InterpolateResource     *Resource
@@ -75,11 +102,11 @@ type MockEvalContext struct {
 	InterpolateProviderError        error
 
 	PathCalled bool
-	PathPath   []string
+	PathPath   addrs.ModuleInstance
 
-	SetVariablesCalled    bool
-	SetVariablesModule    string
-	SetVariablesVariables map[string]interface{}
+	SetModuleCallArgumentsCalled bool
+	SetModuleCallArgumentsModule addrs.ModuleCallInstance
+	SetModuleCallArgumentsValues map[string]cty.Value
 
 	DiffCalled bool
 	DiffDiff   *Diff
@@ -90,6 +117,9 @@ type MockEvalContext struct {
 	StateLock   *sync.RWMutex
 }
 
+// MockEvalContext implements EvalContext
+var _ EvalContext = (*MockEvalContext)(nil)
+
 func (c *MockEvalContext) Stopped() <-chan struct{} {
 	c.StoppedCalled = true
 	return c.StoppedValue
@@ -111,47 +141,48 @@ func (c *MockEvalContext) Input() UIInput {
 	return c.InputInput
 }
 
-func (c *MockEvalContext) InitProvider(t, n string) (ResourceProvider, error) {
+func (c *MockEvalContext) InitProvider(t string, addr addrs.ProviderConfig) (ResourceProvider, error) {
 	c.InitProviderCalled = true
-	c.InitProviderName = n
+	c.InitProviderType = t
+	c.InitProviderAddr = addr
 	return c.InitProviderProvider, c.InitProviderError
 }
 
-func (c *MockEvalContext) Provider(n string) ResourceProvider {
+func (c *MockEvalContext) Provider(addr addrs.AbsProviderConfig) ResourceProvider {
 	c.ProviderCalled = true
-	c.ProviderName = n
+	c.ProviderAddr = addr
 	return c.ProviderProvider
 }
 
-func (c *MockEvalContext) ProviderSchema(n string) *ProviderSchema {
+func (c *MockEvalContext) ProviderSchema(addr addrs.AbsProviderConfig) *ProviderSchema {
 	c.ProviderSchemaCalled = true
-	c.ProviderSchemaName = n
+	c.ProviderSchemaAddr = addr
 	return c.ProviderSchemaSchema
 }
 
-func (c *MockEvalContext) CloseProvider(n string) error {
+func (c *MockEvalContext) CloseProvider(addr addrs.ProviderConfig) error {
 	c.CloseProviderCalled = true
-	c.CloseProviderName = n
+	c.CloseProviderAddr = addr
 	return nil
 }
 
-func (c *MockEvalContext) ConfigureProvider(n string, cfg *ResourceConfig) error {
+func (c *MockEvalContext) ConfigureProvider(addr addrs.ProviderConfig, cfg cty.Value) tfdiags.Diagnostics {
 	c.ConfigureProviderCalled = true
-	c.ConfigureProviderName = n
+	c.ConfigureProviderAddr = addr
 	c.ConfigureProviderConfig = cfg
-	return c.ConfigureProviderError
+	return c.ConfigureProviderDiags
 }
 
-func (c *MockEvalContext) ProviderInput(n string) map[string]interface{} {
+func (c *MockEvalContext) ProviderInput(addr addrs.ProviderConfig) map[string]cty.Value {
 	c.ProviderInputCalled = true
-	c.ProviderInputName = n
-	return c.ProviderInputConfig
+	c.ProviderInputAddr = addr
+	return c.ProviderInputValues
 }
 
-func (c *MockEvalContext) SetProviderInput(n string, cfg map[string]interface{}) {
+func (c *MockEvalContext) SetProviderInput(addr addrs.ProviderConfig, vals map[string]cty.Value) {
 	c.SetProviderInputCalled = true
-	c.SetProviderInputName = n
-	c.SetProviderInputConfig = cfg
+	c.SetProviderInputAddr = addr
+	c.SetProviderInputValues = vals
 }
 
 func (c *MockEvalContext) InitProvisioner(n string) (ResourceProvisioner, error) {
@@ -166,12 +197,34 @@ func (c *MockEvalContext) Provisioner(n string) ResourceProvisioner {
 	return c.ProvisionerProvisioner
 }
 
+func (c *MockEvalContext) ProvisionerSchema(n string) *configschema.Block {
+	c.ProvisionerSchemaCalled = true
+	c.ProvisionerSchemaName = n
+	return c.ProvisionerSchemaSchema
+}
+
 func (c *MockEvalContext) CloseProvisioner(n string) error {
 	c.CloseProvisionerCalled = true
 	c.CloseProvisionerName = n
 	return nil
 }
 
+func (c *MockEvalContext) EvaluateBlock(body hcl.Body, schema *configschema.Block, self addrs.Referenceable) (cty.Value, hcl.Body, tfdiags.Diagnostics) {
+	c.EvaluateBlockCalled = true
+	c.EvaluateBlockBody = body
+	c.EvaluateBlockSchema = schema
+	c.EvaluateBlockSelf = self
+	return c.EvaluateBlockResult, c.EvaluateBlockExpandedBody, c.EvaluateBlockDiags
+}
+
+func (c *MockEvalContext) EvaluateExpr(expr hcl.Expression, wantType cty.Type, self addrs.Referenceable) (cty.Value, tfdiags.Diagnostics) {
+	c.EvaluateExprCalled = true
+	c.EvaluateExprExpr = expr
+	c.EvaluateExprWantType = wantType
+	c.EvaluateExprSelf = self
+	return c.EvaluateExprResult, c.EvaluateExprDiags
+}
+
 func (c *MockEvalContext) Interpolate(
 	config *config.RawConfig, resource *Resource) (*ResourceConfig, error) {
 	c.InterpolateCalled = true
@@ -188,15 +241,15 @@ func (c *MockEvalContext) InterpolateProvider(
 	return c.InterpolateProviderConfigResult, c.InterpolateError
 }
 
-func (c *MockEvalContext) Path() []string {
+func (c *MockEvalContext) Path() addrs.ModuleInstance {
 	c.PathCalled = true
 	return c.PathPath
 }
 
-func (c *MockEvalContext) SetVariables(n string, vs map[string]interface{}) {
-	c.SetVariablesCalled = true
-	c.SetVariablesModule = n
-	c.SetVariablesVariables = vs
+func (c *MockEvalContext) SetModuleCallArguments(n addrs.ModuleCallInstance, values map[string]cty.Value) {
+	c.SetModuleCallArgumentsCalled = true
+	c.SetModuleCallArgumentsModule = n
+	c.SetModuleCallArgumentsValues = values
 }
 
 func (c *MockEvalContext) Diff() (*Diff, *sync.RWMutex) {

terraform/eval_count.go

@@ -1,58 +1,142 @@
 package terraform
 
 import (
-	"github.com/hashicorp/terraform/config"
+	"fmt"
+	"log"
+
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/tfdiags"
+	"github.com/zclconf/go-cty/cty"
+	"github.com/zclconf/go-cty/cty/gocty"
 )
 
-// EvalCountFixZeroOneBoundary is an EvalNode that fixes up the state
-// when there is a resource count with zero/one boundary, i.e. fixing
-// a resource named "aws_instance.foo" to "aws_instance.foo.0" and vice-versa.
-type EvalCountFixZeroOneBoundary struct {
-	Resource *config.Resource
+// evaluateResourceCountExpression is our standard mechanism for interpreting an
+// expression given for a "count" argument on a resource. This should be called
+// from the DynamicExpand of a node representing a resource in order to
+// determine the final count value.
+//
+// If the result is zero or positive and no error diagnostics are returned, then
+// the result is the literal count value to use.
+//
+// If the result is -1, this indicates that the given expression is nil and so
+// the "count" behavior should not be enabled for this resource at all.
+//
+// If error diagnostics are returned then the result is undefined and must
+// not be used.
+func evaluateResourceCountExpression(expr hcl.Expression, ctx EvalContext) (int, tfdiags.Diagnostics) {
+	if expr == nil {
+		return -1, nil
+	}
+
+	var diags tfdiags.Diagnostics
+	var count int
+
+	countVal, countDiags := ctx.EvaluateExpr(expr, cty.Number, nil)
+	diags = diags.Append(countDiags)
+	if diags.HasErrors() {
+		return -1, diags
+	}
+
+	switch {
+	case countVal.IsNull():
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Invalid count argument",
+			Detail:   `The given "count" argument value is null. An integer is required.`,
+			Subject:  expr.Range().Ptr(),
+		})
+		return -1, diags
+	case !countVal.IsKnown():
+		// Currently this is a rather bad outcome from a UX standpoint, since we have
+		// no real mechanism to deal with this situation and all we can do is produce
+		// an error message.
+		// FIXME: In future, implement a built-in mechanism for deferring changes that
+		// can't yet be predicted, and use it to guide the user through several
+		// plan/apply steps until the desired configuration is eventually reached.
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Invalid count argument",
+			Detail:   `The "count" value depends on resource attributes that cannot be determined until apply, so Terraform cannot predict how many instances will be created. To work around this, use the -target argument to first apply only the resources that the count depends on.`,
+			Subject:  expr.Range().Ptr(),
+		})
+		return -1, diags
+	}
+
+	err := gocty.FromCtyValue(countVal, &count)
+	if err != nil {
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Invalid count argument",
+			Detail:   fmt.Sprintf(`The given "count" argument value is unsuitable: %s.`, err),
+			Subject:  expr.Range().Ptr(),
+		})
+		return -1, diags
+	}
+	if count < 0 {
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Invalid count argument",
+			Detail:   `The given "count" argument value is unsuitable: negative numbers are not supported.`,
+			Subject:  expr.Range().Ptr(),
+		})
+		return -1, diags
+	}
+
+	return count, diags
 }
 
-// TODO: test
-func (n *EvalCountFixZeroOneBoundary) Eval(ctx EvalContext) (interface{}, error) {
-	// Get the count, important for knowing whether we're supposed to
-	// be adding the zero, or trimming it.
-	count, err := n.Resource.Count()
-	if err != nil {
-		return nil, err
+// fixResourceCountSetTransition is a helper function to fix up the state when a
+// resource transitions its "count" from being set to unset or vice-versa,
+// treating a 0-key and a no-key instance as aliases for one another across
+// the transition.
+//
+// The correct time to call this function is in the DynamicExpand method for
+// a node representing a resource, just after evaluating the count with
+// evaluateResourceCountExpression, and before any other analysis of the
+// state such as orphan detection.
+//
+// This function calls methods on the given EvalContext to update the current
+// state in-place, if necessary. It is a no-op if there is no count transition
+// taking place.
+//
+// Since the state is modified in-place, this function must take a writer lock
+// on the state. The caller must therefore not also be holding a state lock,
+// or this function will block forever awaiting the lock.
+func fixResourceCountSetTransition(ctx EvalContext, addr addrs.Resource, countEnabled bool) {
+	huntAddr := addr.Instance(addrs.NoKey)
+	replaceAddr := addr.Instance(addrs.IntKey(0))
+	if !countEnabled {
+		huntAddr, replaceAddr = replaceAddr, huntAddr
 	}
 
-	// Figure what to look for and what to replace it with
-	hunt := n.Resource.Id()
-	replace := hunt + ".0"
-	if count < 2 {
-		hunt, replace = replace, hunt
-	}
+	path := ctx.Path()
+
+	// The state still uses our legacy internal address string format, so we
+	// need to shim here.
+	huntKey := NewLegacyResourceInstanceAddress(huntAddr.Absolute(path)).stateId()
+	replaceKey := NewLegacyResourceInstanceAddress(replaceAddr.Absolute(path)).stateId()
 
 	state, lock := ctx.State()
-
-	// Get a lock so we can access this instance and potentially make
-	// changes to it.
 	lock.Lock()
 	defer lock.Unlock()
 
-	// Look for the module state. If we don't have one, then it doesn't matter.
-	mod := state.ModuleByPath(ctx.Path())
+	mod := state.ModuleByPath(path)
 	if mod == nil {
-		return nil, nil
+		return
 	}
 
-	// Look for the resource state. If we don't have one, then it is okay.
-	rs, ok := mod.Resources[hunt]
+	rs, ok := mod.Resources[huntKey]
 	if !ok {
-		return nil, nil
+		return
 	}
 
-	// If the replacement key exists, we just keep both
-	if _, ok := mod.Resources[replace]; ok {
-		return nil, nil
+	// If the replacement key also exists then we do nothing and keep both.
+	if _, ok := mod.Resources[replaceKey]; ok {
+		return
 	}
 
-	mod.Resources[replace] = rs
-	delete(mod.Resources, hunt)
-
-	return nil, nil
+	mod.Resources[replaceKey] = rs
+	delete(mod.Resources, huntKey)
+	log.Printf("[TRACE] renamed %s to %s in transient state due to count argument change", huntKey, replaceKey)
 }

terraform/eval_diff.go

@@ -1,18 +1,24 @@
 package terraform
 
 import (
+	"bytes"
 	"fmt"
 	"log"
 	"strings"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/zclconf/go-cty/cty"
+
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/tfdiags"
 	"github.com/hashicorp/terraform/version"
 )
 
 // EvalCompareDiff is an EvalNode implementation that compares two diffs
 // and errors if the diffs are not equal.
 type EvalCompareDiff struct {
-	Info     *InstanceInfo
+	Addr     addrs.ResourceInstance
 	One, Two **InstanceDiff
 }
 
@@ -43,10 +49,10 @@ func (n *EvalCompareDiff) Eval(ctx EvalContext) (interface{}, error) {
 	}()
 
 	if same, reason := one.Same(two); !same {
-		log.Printf("[ERROR] %s: diffs didn't match", n.Info.Id)
-		log.Printf("[ERROR] %s: reason: %s", n.Info.Id, reason)
-		log.Printf("[ERROR] %s: diff one: %#v", n.Info.Id, one)
-		log.Printf("[ERROR] %s: diff two: %#v", n.Info.Id, two)
+		log.Printf("[ERROR] %s: diffs didn't match", n.Addr)
+		log.Printf("[ERROR] %s: reason: %s", n.Addr, reason)
+		log.Printf("[ERROR] %s: diff one: %#v", n.Addr, one)
+		log.Printf("[ERROR] %s: diff two: %#v", n.Addr, two)
 		return nil, fmt.Errorf(
 			"%s: diffs didn't match during apply. This is a bug with "+
 				"Terraform and should be reported as a GitHub Issue.\n"+
@@ -61,7 +67,7 @@ func (n *EvalCompareDiff) Eval(ctx EvalContext) (interface{}, error) {
 				"\n"+
 				"Also include as much context as you can about your config, state, "+
 				"and the steps you performed to trigger this error.\n",
-			n.Info.Id, version.Version, n.Info.Id, reason, one, two)
+			n.Addr, version.Version, n.Addr, reason, one, two)
 	}
 
 	return nil, nil
@@ -70,23 +76,17 @@ func (n *EvalCompareDiff) Eval(ctx EvalContext) (interface{}, error) {
 // EvalDiff is an EvalNode implementation that does a refresh for
 // a resource.
 type EvalDiff struct {
-	Name        string
-	Info        *InstanceInfo
-	Config      **ResourceConfig
-	Provider    *ResourceProvider
-	Diff        **InstanceDiff
-	State       **InstanceState
+	Addr           addrs.ResourceInstance
+	Config         *configs.Resource
+	Provider       *ResourceProvider
+	ProviderSchema **ProviderSchema
+	State          **InstanceState
+	PreviousDiff   **InstanceDiff
+
 	OutputDiff  **InstanceDiff
+	OutputValue *cty.Value
 	OutputState **InstanceState
 
-	// Resource is needed to fetch the ignore_changes list so we can
-	// filter user-requested ignored attributes from the diff.
-	Resource *config.Resource
-
-	// Stub is used to flag the generated InstanceDiff as a stub. This is used to
-	// ensure that the node exists to perform interpolations and generate
-	// computed paths off of, but not as an actual diff where resouces should be
-	// counted, and not as a diff that should be acted on.
 	Stub bool
 }
 
@@ -95,11 +95,21 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 	state := *n.State
 	config := *n.Config
 	provider := *n.Provider
+	providerSchema := *n.ProviderSchema
+
+	var diags tfdiags.Diagnostics
+
+	// The provider and hook APIs still expect our legacy InstanceInfo type.
+	legacyInfo := NewInstanceInfo(n.Addr.Absolute(ctx.Path()).ContainingResource())
+
+	// State still uses legacy-style internal ids, so we need to shim to get
+	// a suitable key to use.
+	stateId := NewLegacyResourceInstanceAddress(n.Addr.Absolute(ctx.Path())).stateId()
 
 	// Call pre-diff hook
 	if !n.Stub {
 		err := ctx.Hook(func(h Hook) (HookAction, error) {
-			return h.PreDiff(n.Info, state)
+			return h.PreDiff(legacyInfo, state)
 		})
 		if err != nil {
 			return nil, err
@@ -113,8 +123,23 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 	}
 	diffState.init()
 
+	// Evaluate the configuration
+	schema := providerSchema.ResourceTypes[n.Addr.Resource.Type]
+	if schema == nil {
+		// Should be caught during validation, so we don't bother with a pretty error here
+		return nil, fmt.Errorf("provider does not support resource type %q", n.Addr.Resource.Type)
+	}
+	configVal, _, configDiags := ctx.EvaluateBlock(config.Config, schema, nil)
+	diags = diags.Append(configDiags)
+	if configDiags.HasErrors() {
+		return nil, diags.Err()
+	}
+
+	// The provider API still expects our legacy ResourceConfig type.
+	legacyRC := NewResourceConfigShimmed(configVal, schema)
+
 	// Diff!
-	diff, err := provider.Diff(n.Info, diffState, config)
+	diff, err := provider.Diff(legacyInfo, diffState, legacyRC)
 	if err != nil {
 		return nil, err
 	}
@@ -123,7 +148,7 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 	}
 
 	// Set DestroyDeposed if we have deposed instances
-	_, err = readInstanceFromState(ctx, n.Name, nil, func(rs *ResourceState) (*InstanceState, error) {
+	_, err = readInstanceFromState(ctx, stateId, nil, func(rs *ResourceState) (*InstanceState, error) {
 		if len(rs.Deposed) > 0 {
 			diff.DestroyDeposed = true
 		}
@@ -135,8 +160,8 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 	}
 
 	// Preserve the DestroyTainted flag
-	if n.Diff != nil {
-		diff.SetTainted((*n.Diff).GetDestroyTainted())
+	if n.PreviousDiff != nil {
+		diff.SetTainted((*n.PreviousDiff).GetDestroyTainted())
 	}
 
 	// Require a destroy if there is an ID and it requires new.
@@ -161,7 +186,7 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 		})
 	}
 
-	// filter out ignored resources
+	// filter out ignored attributes
 	if err := n.processIgnoreChanges(diff); err != nil {
 		return nil, err
 	}
@@ -169,7 +194,7 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 	// Call post-refresh hook
 	if !n.Stub {
 		err = ctx.Hook(func(h Hook) (HookAction, error) {
-			return h.PostDiff(n.Info, diff)
+			return h.PostDiff(legacyInfo, diff)
 		})
 		if err != nil {
 			return nil, err
@@ -181,6 +206,10 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 		*n.OutputDiff = diff
 	}
 
+	if n.OutputValue != nil {
+		*n.OutputValue = configVal
+	}
+
 	// Update the state if we care
 	if n.OutputState != nil {
 		*n.OutputState = state
@@ -195,12 +224,13 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 }
 
 func (n *EvalDiff) processIgnoreChanges(diff *InstanceDiff) error {
-	if diff == nil || n.Resource == nil || n.Resource.Id() == "" {
+	if diff == nil || n.Config == nil || n.Config.Managed == nil {
 		return nil
 	}
-	ignoreChanges := n.Resource.Lifecycle.IgnoreChanges
+	ignoreChanges := n.Config.Managed.IgnoreChanges
+	ignoreAll := n.Config.Managed.IgnoreAllChanges
 
-	if len(ignoreChanges) == 0 {
+	if len(ignoreChanges) == 0 && !ignoreAll {
 		return nil
 	}
 
@@ -220,9 +250,10 @@ func (n *EvalDiff) processIgnoreChanges(diff *InstanceDiff) error {
 
 	// get the complete set of keys we want to ignore
 	ignorableAttrKeys := make(map[string]bool)
-	for _, ignoredKey := range ignoreChanges {
+	for _, ignoredTraversal := range ignoreChanges {
+		ignoredKey := legacyFlatmapKeyForTraversal(ignoredTraversal)
 		for k := range attrs {
-			if ignoredKey == "*" || strings.HasPrefix(k, ignoredKey) {
+			if ignoreAll || strings.HasPrefix(k, ignoredKey) {
 				ignorableAttrKeys[k] = true
 			}
 		}
@@ -285,14 +316,56 @@ func (n *EvalDiff) processIgnoreChanges(diff *InstanceDiff) error {
 
 	// If we didn't hit any of our early exit conditions, we can filter the diff.
 	for k := range ignorableAttrKeys {
-		log.Printf("[DEBUG] [EvalIgnoreChanges] %s - Ignoring diff attribute: %s",
-			n.Resource.Id(), k)
+		log.Printf("[DEBUG] [EvalIgnoreChanges] %s: Ignoring diff attribute: %s", n.Addr.String(), k)
 		diff.DelAttribute(k)
 	}
 
 	return nil
 }
 
+// legacyFlagmapKeyForTraversal constructs a key string compatible with what
+// the flatmap package would generate for an attribute addressable by the given
+// traversal.
+//
+// This is used only to shim references to attributes within the diff and
+// state structures, which have not (at the time of writing) yet been updated
+// to use the newer HCL-based representations.
+func legacyFlatmapKeyForTraversal(traversal hcl.Traversal) string {
+	var buf bytes.Buffer
+	first := true
+	for _, step := range traversal {
+		if !first {
+			buf.WriteByte('.')
+		}
+		switch ts := step.(type) {
+		case hcl.TraverseRoot:
+			buf.WriteString(ts.Name)
+		case hcl.TraverseAttr:
+			buf.WriteString(ts.Name)
+		case hcl.TraverseIndex:
+			val := ts.Key
+			switch val.Type() {
+			case cty.Number:
+				bf := val.AsBigFloat()
+				buf.WriteString(bf.String())
+			case cty.String:
+				s := val.AsString()
+				buf.WriteString(s)
+			default:
+				// should never happen, since no other types appear in
+				// traversals in practice.
+				buf.WriteByte('?')
+			}
+		default:
+			// should never happen, since we've covered all of the types
+			// that show up in parsed traversals in practice.
+			buf.WriteByte('?')
+		}
+		first = false
+	}
+	return buf.String()
+}
+
 // a group of key-*ResourceAttrDiff pairs from the same flatmapped container
 type flatAttrDiff map[string]*ResourceAttrDiff
 
@@ -343,7 +416,7 @@ func groupContainers(d *InstanceDiff) map[string]flatAttrDiff {
 // EvalDiffDestroy is an EvalNode implementation that returns a plain
 // destroy diff.
 type EvalDiffDestroy struct {
-	Info   *InstanceInfo
+	Addr   addrs.ResourceInstance
 	State  **InstanceState
 	Output **InstanceDiff
 }
@@ -357,9 +430,12 @@ func (n *EvalDiffDestroy) Eval(ctx EvalContext) (interface{}, error) {
 		return nil, nil
 	}
 
+	// The provider and hook APIs still expect our legacy InstanceInfo type.
+	legacyInfo := NewInstanceInfo(n.Addr.Absolute(ctx.Path()).ContainingResource())
+
 	// Call pre-diff hook
 	err := ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PreDiff(n.Info, state)
+		return h.PreDiff(legacyInfo, state)
 	})
 	if err != nil {
 		return nil, err
@@ -370,7 +446,7 @@ func (n *EvalDiffDestroy) Eval(ctx EvalContext) (interface{}, error) {
 
 	// Call post-diff hook
 	err = ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PostDiff(n.Info, diff)
+		return h.PostDiff(legacyInfo, diff)
 	})
 	if err != nil {
 		return nil, err
@@ -385,7 +461,7 @@ func (n *EvalDiffDestroy) Eval(ctx EvalContext) (interface{}, error) {
 // EvalDiffDestroyModule is an EvalNode implementation that writes the diff to
 // the full diff.
 type EvalDiffDestroyModule struct {
-	Path []string
+	Path addrs.ModuleInstance
 }
 
 // TODO: test

terraform/eval_import_state.go

@@ -2,6 +2,8 @@ package terraform
 
 import (
 	"fmt"
+
+	"github.com/hashicorp/terraform/addrs"
 )
 
 // EvalImportState is an EvalNode implementation that performs an
@@ -55,7 +57,7 @@ func (n *EvalImportState) Eval(ctx EvalContext) (interface{}, error) {
 // EvalImportStateVerify verifies the state after ImportState and
 // after the refresh to make sure it is non-nil and valid.
 type EvalImportStateVerify struct {
-	Info  *InstanceInfo
+	Addr  addrs.ResourceInstance
 	Id    string
 	State **InstanceState
 }
@@ -68,7 +70,7 @@ func (n *EvalImportStateVerify) Eval(ctx EvalContext) (interface{}, error) {
 			"import %s (id: %s): Terraform detected a resource with this ID doesn't\n"+
 				"exist. Please verify the ID is correct. You cannot import non-existent\n"+
 				"resources using Terraform import.",
-			n.Info.HumanId(),
+			n.Addr.String(),
 			n.Id)
 	}
 

terraform/eval_interpolate.go

@@ -1,56 +0,0 @@
-package terraform
-
-import (
-	"log"
-
-	"github.com/hashicorp/terraform/config"
-)
-
-// EvalInterpolate is an EvalNode implementation that takes a raw
-// configuration and interpolates it.
-type EvalInterpolate struct {
-	Config        *config.RawConfig
-	Resource      *Resource
-	Output        **ResourceConfig
-	ContinueOnErr bool
-}
-
-func (n *EvalInterpolate) Eval(ctx EvalContext) (interface{}, error) {
-	rc, err := ctx.Interpolate(n.Config, n.Resource)
-	if err != nil {
-		if n.ContinueOnErr {
-			log.Printf("[WARN] Interpolation %q failed: %s", n.Config.Key, err)
-			return nil, EvalEarlyExitError{}
-		}
-		return nil, err
-	}
-
-	if n.Output != nil {
-		*n.Output = rc
-	}
-
-	return nil, nil
-}
-
-// EvalInterpolateProvider is an EvalNode implementation that takes a
-// ProviderConfig and interpolates it. Provider configurations are the only
-// "inherited" type of configuration we have, and the original raw config may
-// have a different interpolation scope.
-type EvalInterpolateProvider struct {
-	Config   *config.ProviderConfig
-	Resource *Resource
-	Output   **ResourceConfig
-}
-
-func (n *EvalInterpolateProvider) Eval(ctx EvalContext) (interface{}, error) {
-	rc, err := ctx.InterpolateProvider(n.Config, n.Resource)
-	if err != nil {
-		return nil, err
-	}
-
-	if n.Output != nil {
-		*n.Output = rc
-	}
-
-	return nil, nil
-}

terraform/eval_interpolate_test.go

@@ -1,37 +0,0 @@
-package terraform
-
-import (
-	"reflect"
-	"testing"
-
-	"github.com/hashicorp/terraform/config"
-)
-
-func TestEvalInterpolate_impl(t *testing.T) {
-	var _ EvalNode = new(EvalInterpolate)
-}
-
-func TestEvalInterpolate(t *testing.T) {
-	config, err := config.NewRawConfig(map[string]interface{}{})
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	var actual *ResourceConfig
-	n := &EvalInterpolate{Config: config, Output: &actual}
-	result := testResourceConfig(t, map[string]interface{}{})
-	ctx := &MockEvalContext{InterpolateConfigResult: result}
-	if _, err := n.Eval(ctx); err != nil {
-		t.Fatalf("err: %s", err)
-	}
-	if actual != result {
-		t.Fatalf("bad: %#v", actual)
-	}
-
-	if !ctx.InterpolateCalled {
-		t.Fatal("should be called")
-	}
-	if !reflect.DeepEqual(ctx.InterpolateConfig, config) {
-		t.Fatalf("bad: %#v", ctx.InterpolateConfig)
-	}
-}

terraform/eval_lang.go

@@ -0,0 +1,61 @@
+package terraform
+
+import (
+	"log"
+
+	"github.com/hashicorp/terraform/addrs"
+
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/config/configschema"
+	"github.com/zclconf/go-cty/cty"
+)
+
+// EvalConfigBlock is an EvalNode implementation that takes a raw
+// configuration block and evaluates any expressions within it.
+//
+// ExpandedConfig is populated with the result of expanding any "dynamic"
+// blocks in the given body, which can be useful for extracting correct source
+// location information for specific attributes in the result.
+type EvalConfigBlock struct {
+	Config         *hcl.Body
+	Schema         *configschema.Block
+	SelfAddr       addrs.Referenceable
+	Output         *cty.Value
+	ExpandedConfig *hcl.Body
+	ContinueOnErr  bool
+}
+
+func (n *EvalConfigBlock) Eval(ctx EvalContext) (interface{}, error) {
+	val, body, diags := ctx.EvaluateBlock(*n.Config, n.Schema, n.SelfAddr)
+	if diags.HasErrors() && n.ContinueOnErr {
+		log.Printf("[WARN] Block evaluation failed: %s", diags.Err())
+		return nil, EvalEarlyExitError{}
+	}
+
+	if n.Output != nil {
+		*n.Output = val
+	}
+	if n.ExpandedConfig != nil {
+		*n.ExpandedConfig = body
+	}
+
+	return nil, diags.ErrWithWarnings()
+}
+
+// EvalConfigExpr is an EvalNode implementation that takes a raw configuration
+// expression and evaluates it.
+type EvalConfigExpr struct {
+	Expr     hcl.Expression
+	SelfAddr addrs.Referenceable
+	Output   *cty.Value
+}
+
+func (n *EvalConfigExpr) Eval(ctx EvalContext) (interface{}, error) {
+	val, diags := ctx.EvaluateExpr(n.Expr, cty.DynamicPseudoType, n.SelfAddr)
+
+	if n.Output != nil {
+		*n.Output = val
+	}
+
+	return nil, diags.ErrWithWarnings()
+}

terraform/eval_local.go

@@ -3,21 +3,24 @@ package terraform
 import (
 	"fmt"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/config/hcl2shim"
+	"github.com/zclconf/go-cty/cty"
 )
 
 // EvalLocal is an EvalNode implementation that evaluates the
 // expression for a local value and writes it into a transient part of
 // the state.
 type EvalLocal struct {
-	Name  string
-	Value *config.RawConfig
+	Addr addrs.LocalValue
+	Expr hcl.Expression
 }
 
 func (n *EvalLocal) Eval(ctx EvalContext) (interface{}, error) {
-	cfg, err := ctx.Interpolate(n.Value, nil)
-	if err != nil {
-		return nil, fmt.Errorf("local.%s: %s", n.Name, err)
+	val, diags := ctx.EvaluateExpr(n.Expr, cty.DynamicPseudoType, nil)
+	if diags.HasErrors() {
+		return nil, diags.Err()
 	}
 
 	state, lock := ctx.State()
@@ -35,24 +38,15 @@ func (n *EvalLocal) Eval(ctx EvalContext) (interface{}, error) {
 		mod = state.AddModule(ctx.Path())
 	}
 
-	// Get the value from the config
-	var valueRaw interface{} = config.UnknownVariableValue
-	if cfg != nil {
-		var ok bool
-		valueRaw, ok = cfg.Get("value")
-		if !ok {
-			valueRaw = ""
-		}
-		if cfg.IsComputed("value") {
-			valueRaw = config.UnknownVariableValue
-		}
-	}
+	// Lower the value to the legacy form that our state structures still expect.
+	// FIXME: Update mod.Locals to be a map[string]cty.Value .
+	legacyVal := hcl2shim.ConfigValueFromHCL2(val)
 
 	if mod.Locals == nil {
 		// initialize
 		mod.Locals = map[string]interface{}{}
 	}
-	mod.Locals[n.Name] = valueRaw
+	mod.Locals[n.Addr.Name] = legacyVal
 
 	return nil, nil
 }
@@ -61,7 +55,7 @@ func (n *EvalLocal) Eval(ctx EvalContext) (interface{}, error) {
 // from the state. Locals aren't persisted, but we don't need to evaluate them
 // during destroy.
 type EvalDeleteLocal struct {
-	Name string
+	Addr addrs.LocalValue
 }
 
 func (n *EvalDeleteLocal) Eval(ctx EvalContext) (interface{}, error) {
@@ -80,7 +74,7 @@ func (n *EvalDeleteLocal) Eval(ctx EvalContext) (interface{}, error) {
 		return nil, nil
 	}
 
-	delete(mod.Locals, n.Name)
+	delete(mod.Locals, n.Addr.Name)
 
 	return nil, nil
 }

terraform/eval_output.go

@@ -4,13 +4,18 @@ import (
 	"fmt"
 	"log"
 
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/config/hcl2shim"
+	"github.com/zclconf/go-cty/cty"
+	"github.com/zclconf/go-cty/cty/gocty"
 )
 
 // EvalDeleteOutput is an EvalNode implementation that deletes an output
 // from the state.
 type EvalDeleteOutput struct {
-	Name string
+	Addr addrs.OutputValue
 }
 
 // TODO: test
@@ -30,7 +35,7 @@ func (n *EvalDeleteOutput) Eval(ctx EvalContext) (interface{}, error) {
 		return nil, nil
 	}
 
-	delete(mod.Outputs, n.Name)
+	delete(mod.Outputs, n.Addr.Name)
 
 	return nil, nil
 }
@@ -38,19 +43,19 @@ func (n *EvalDeleteOutput) Eval(ctx EvalContext) (interface{}, error) {
 // EvalWriteOutput is an EvalNode implementation that writes the output
 // for the given name to the current state.
 type EvalWriteOutput struct {
-	Name      string
+	Addr      addrs.OutputValue
 	Sensitive bool
-	Value     *config.RawConfig
+	Expr      hcl.Expression
 	// ContinueOnErr allows interpolation to fail during Input
 	ContinueOnErr bool
 }
 
 // TODO: test
 func (n *EvalWriteOutput) Eval(ctx EvalContext) (interface{}, error) {
-	// This has to run before we have a state lock, since interpolation also
+	// This has to run before we have a state lock, since evaluation also
 	// reads the state
-	cfg, err := ctx.Interpolate(n.Value, nil)
-	// handle the error after we have the module from the state
+	val, diags := ctx.EvaluateExpr(n.Expr, cty.DynamicPseudoType, nil)
+	// We'll handle errors below, after we have loaded the module.
 
 	state, lock := ctx.State()
 	if state == nil {
@@ -67,67 +72,66 @@ func (n *EvalWriteOutput) Eval(ctx EvalContext) (interface{}, error) {
 	}
 
 	// handling the interpolation error
-	if err != nil {
+	if diags.HasErrors() {
 		if n.ContinueOnErr || flagWarnOutputErrors {
-			log.Printf("[ERROR] Output interpolation %q failed: %s", n.Name, err)
+			log.Printf("[ERROR] Output interpolation %q failed: %s", n.Addr.Name, diags.Err())
 			// if we're continuing, make sure the output is included, and
 			// marked as unknown
-			mod.Outputs[n.Name] = &OutputState{
+			mod.Outputs[n.Addr.Name] = &OutputState{
 				Type:  "string",
 				Value: config.UnknownVariableValue,
 			}
 			return nil, EvalEarlyExitError{}
 		}
-		return nil, err
+		return nil, diags.Err()
 	}
 
-	// Get the value from the config
-	var valueRaw interface{} = config.UnknownVariableValue
-	if cfg != nil {
-		var ok bool
-		valueRaw, ok = cfg.Get("value")
-		if !ok {
-			valueRaw = ""
+	ty := val.Type()
+	switch {
+	case ty.IsPrimitiveType():
+		// For now we record all primitive types as strings, for compatibility
+		// with our existing state formats.
+		// FIXME: Revise the state format to support any type.
+		var valueTyped string
+		switch {
+		case !val.IsKnown():
+			// Legacy handling of unknown values as a special string.
+			valueTyped = config.UnknownVariableValue
+		case val.IsNull():
+			// State doesn't currently support null, so we'll save as empty string.
+			valueTyped = ""
+		default:
+			err := gocty.FromCtyValue(val, &valueTyped)
+			if err != nil {
+				// Should never happen, because all primitives can convert to string.
+				return nil, fmt.Errorf("cannot marshal %#v for storage in state: %s", err)
+			}
 		}
-		if cfg.IsComputed("value") {
-			valueRaw = config.UnknownVariableValue
-		}
-	}
-
-	switch valueTyped := valueRaw.(type) {
-	case string:
-		mod.Outputs[n.Name] = &OutputState{
+		mod.Outputs[n.Addr.Name] = &OutputState{
 			Type:      "string",
 			Sensitive: n.Sensitive,
 			Value:     valueTyped,
 		}
-	case []interface{}:
-		mod.Outputs[n.Name] = &OutputState{
+	case ty.IsListType() || ty.IsTupleType() || ty.IsSetType():
+		// For now we'll use our legacy storage forms for list-like types.
+		// This produces a []interface{}.
+		valueTyped := hcl2shim.ConfigValueFromHCL2(val)
+		mod.Outputs[n.Addr.Name] = &OutputState{
 			Type:      "list",
 			Sensitive: n.Sensitive,
 			Value:     valueTyped,
 		}
-	case map[string]interface{}:
-		mod.Outputs[n.Name] = &OutputState{
+	case ty.IsMapType() || ty.IsObjectType():
+		// For now we'll use our legacy storage forms for map-like types.
+		// This produces a map[string]interface{}.
+		valueTyped := hcl2shim.ConfigValueFromHCL2(val)
+		mod.Outputs[n.Addr.Name] = &OutputState{
 			Type:      "map",
 			Sensitive: n.Sensitive,
 			Value:     valueTyped,
 		}
-	case []map[string]interface{}:
-		// an HCL map is multi-valued, so if this was read out of a config the
-		// map may still be in a slice.
-		if len(valueTyped) == 1 {
-			mod.Outputs[n.Name] = &OutputState{
-				Type:      "map",
-				Sensitive: n.Sensitive,
-				Value:     valueTyped[0],
-			}
-			break
-		}
-		return nil, fmt.Errorf("output %s type (%T) with %d values not valid for type map",
-			n.Name, valueTyped, len(valueTyped))
 	default:
-		return nil, fmt.Errorf("output %s is not a valid type (%T)\n", n.Name, valueTyped)
+		return nil, fmt.Errorf("output %s is not a valid type (%s)", n.Addr.Name, ty.FriendlyName())
 	}
 
 	return nil, nil

terraform/eval_provider.go

@@ -3,49 +3,68 @@ package terraform
 import (
 	"fmt"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/zclconf/go-cty/cty"
+
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
-// EvalBuildProviderConfig outputs a *ResourceConfig that is properly
-// merged with parents and inputs on top of what is configured in the file.
-type EvalBuildProviderConfig struct {
-	Provider string
-	Config   **ResourceConfig
-	Output   **ResourceConfig
-}
-
-func (n *EvalBuildProviderConfig) Eval(ctx EvalContext) (interface{}, error) {
-	cfg := *n.Config
-
+func buildProviderConfig(ctx EvalContext, addr addrs.ProviderConfig, body hcl.Body) hcl.Body {
 	// If we have an Input configuration set, then merge that in
-	if input := ctx.ProviderInput(n.Provider); input != nil {
+	if input := ctx.ProviderInput(addr); input != nil {
 		// "input" is a map of the subset of config values that were known
 		// during the input walk, set by EvalInputProvider. Note that
 		// in particular it does *not* include attributes that had
 		// computed values at input time; those appear *only* in
 		// "cfg" here.
-		rc, err := config.NewRawConfig(input)
-		if err != nil {
-			return nil, err
-		}
 
-		merged := rc.Merge(cfg.raw)
-		cfg = NewResourceConfig(merged)
+		inputBody := configs.SynthBody("<input prompt>", input)
+		body = configs.MergeBodies(body, inputBody)
 	}
 
-	*n.Output = cfg
-	return nil, nil
+	return body
 }
 
 // EvalConfigProvider is an EvalNode implementation that configures
 // a provider that is already initialized and retrieved.
 type EvalConfigProvider struct {
-	Provider string
-	Config   **ResourceConfig
+	Addr     addrs.ProviderConfig
+	Provider *ResourceProvider
+	Config   *configs.Provider
 }
 
 func (n *EvalConfigProvider) Eval(ctx EvalContext) (interface{}, error) {
-	return nil, ctx.ConfigureProvider(n.Provider, *n.Config)
+	var diags tfdiags.Diagnostics
+	provider := *n.Provider
+	config := n.Config
+
+	if config == nil {
+		// If we have no explicit configuration, just write an empty
+		// configuration into the provider.
+		configDiags := ctx.ConfigureProvider(n.Addr, cty.EmptyObjectVal)
+		return nil, configDiags.ErrWithWarnings()
+	}
+
+	schema, err := provider.GetSchema(&ProviderSchemaRequest{})
+	if err != nil {
+		diags = diags.Append(err)
+		return nil, diags.NonFatalErr()
+	}
+
+	configSchema := schema.Provider
+	configBody := buildProviderConfig(ctx, n.Addr, config.Config)
+	configVal, configBody, evalDiags := ctx.EvaluateBlock(configBody, configSchema, nil)
+	diags = diags.Append(evalDiags)
+	if evalDiags.HasErrors() {
+		return nil, diags.NonFatalErr()
+	}
+
+	configDiags := ctx.ConfigureProvider(n.Addr, configVal)
+	configDiags = configDiags.InConfigBody(configBody)
+
+	return nil, configDiags.ErrWithWarnings()
 }
 
 // EvalInitProvider is an EvalNode implementation that initializes a provider
@@ -53,85 +72,73 @@ func (n *EvalConfigProvider) Eval(ctx EvalContext) (interface{}, error) {
 // EvalGetProvider node.
 type EvalInitProvider struct {
 	TypeName string
-	Name     string
+	Addr     addrs.ProviderConfig
 }
 
 func (n *EvalInitProvider) Eval(ctx EvalContext) (interface{}, error) {
-	return ctx.InitProvider(n.TypeName, n.Name)
+	return ctx.InitProvider(n.TypeName, n.Addr)
 }
 
 // EvalCloseProvider is an EvalNode implementation that closes provider
 // connections that aren't needed anymore.
 type EvalCloseProvider struct {
-	Name string
+	Addr addrs.ProviderConfig
 }
 
 func (n *EvalCloseProvider) Eval(ctx EvalContext) (interface{}, error) {
-	ctx.CloseProvider(n.Name)
+	ctx.CloseProvider(n.Addr)
 	return nil, nil
 }
 
 // EvalGetProvider is an EvalNode implementation that retrieves an already
 // initialized provider instance for the given name.
+//
+// Unlike most eval nodes, this takes an _absolute_ provider configuration,
+// because providers can be passed into and inherited between modules.
+// Resource nodes must therefore know the absolute path of the provider they
+// will use, which is usually accomplished by implementing
+// interface GraphNodeProviderConsumer.
 type EvalGetProvider struct {
-	Name   string
+	Addr   addrs.AbsProviderConfig
 	Output *ResourceProvider
+
+	// If non-nil, Schema will be updated after eval to refer to the
+	// schema of the provider.
+	Schema **ProviderSchema
 }
 
 func (n *EvalGetProvider) Eval(ctx EvalContext) (interface{}, error) {
-	result := ctx.Provider(n.Name)
+	result := ctx.Provider(n.Addr)
 	if result == nil {
-		return nil, fmt.Errorf("provider %s not initialized", n.Name)
+		return nil, fmt.Errorf("provider %s not initialized", n.Addr)
 	}
 
 	if n.Output != nil {
 		*n.Output = result
 	}
 
+	if n.Schema != nil {
+		*n.Schema = ctx.ProviderSchema(n.Addr)
+	}
+
 	return nil, nil
 }
 
 // EvalInputProvider is an EvalNode implementation that asks for input
 // for the given provider configurations.
 type EvalInputProvider struct {
-	Name     string
+	Addr     addrs.ProviderConfig
 	Provider *ResourceProvider
-	Config   **ResourceConfig
+	Config   *configs.Provider
 }
 
 func (n *EvalInputProvider) Eval(ctx EvalContext) (interface{}, error) {
-	rc := *n.Config
-	orig := rc.DeepCopy()
-
-	// Wrap the input into a namespace
-	input := &PrefixUIInput{
-		IdPrefix:    fmt.Sprintf("provider.%s", n.Name),
-		QueryPrefix: fmt.Sprintf("provider.%s.", n.Name),
-		UIInput:     ctx.Input(),
-	}
-
-	// Go through each provider and capture the input necessary
-	// to satisfy it.
-	config, err := (*n.Provider).Input(input, rc)
-	if err != nil {
-		return nil, fmt.Errorf(
-			"Error configuring %s: %s", n.Name, err)
-	}
-
-	// We only store values that have changed through Input.
-	// The goal is to cache cache input responses, not to provide a complete
-	// config for other providers.
-	confMap := make(map[string]interface{})
-	if config != nil && len(config.Config) > 0 {
-		// any values that weren't in the original ResourcConfig will be cached
-		for k, v := range config.Config {
-			if _, ok := orig.Config[k]; !ok {
-				confMap[k] = v
-			}
-		}
-	}
-
-	ctx.SetProviderInput(n.Name, confMap)
-
-	return nil, nil
+	// This is currently disabled. It used to interact with a provider method
+	// called Input, allowing the provider to capture input interactively
+	// itself, but once re-implemented we'll have this instead use the
+	// provider's configuration schema to automatically infer what we need
+	// to prompt for.
+	var diags tfdiags.Diagnostics
+	diags = diags.Append(tfdiags.SimpleWarning(fmt.Sprintf("%s: provider input is temporarily disabled", n.Addr)))
+	return nil, diags.ErrWithWarnings()
 }

terraform/eval_provisioner.go

@@ -2,6 +2,8 @@ package terraform
 
 import (
 	"fmt"
+
+	"github.com/hashicorp/terraform/config/configschema"
 )
 
 // EvalInitProvisioner is an EvalNode implementation that initializes a provisioner
@@ -31,6 +33,7 @@ func (n *EvalCloseProvisioner) Eval(ctx EvalContext) (interface{}, error) {
 type EvalGetProvisioner struct {
 	Name   string
 	Output *ResourceProvisioner
+	Schema **configschema.Block
 }
 
 func (n *EvalGetProvisioner) Eval(ctx EvalContext) (interface{}, error) {
@@ -43,5 +46,9 @@ func (n *EvalGetProvisioner) Eval(ctx EvalContext) (interface{}, error) {
 		*n.Output = result
 	}
 
+	if n.Schema != nil {
+		*n.Schema = ctx.ProvisionerSchema(n.Name)
+	}
+
 	return result, nil
 }

terraform/eval_read_data.go

@@ -2,16 +2,25 @@ package terraform
 
 import (
 	"fmt"
+
+	"github.com/hashicorp/terraform/tfdiags"
+
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/zclconf/go-cty/cty"
 )
 
 // EvalReadDataDiff is an EvalNode implementation that executes a data
 // resource's ReadDataDiff method to discover what attributes it exports.
 type EvalReadDataDiff struct {
-	Provider    *ResourceProvider
+	Addr           addrs.ResourceInstance
+	Config         *configs.Resource
+	Provider       *ResourceProvider
+	ProviderSchema **ProviderSchema
+
 	Output      **InstanceDiff
+	OutputValue *cty.Value
 	OutputState **InstanceState
-	Config      **ResourceConfig
-	Info        *InstanceInfo
 
 	// Set Previous when re-evaluating diff during apply, to ensure that
 	// the "Destroy" flag is preserved.
@@ -21,14 +30,20 @@ type EvalReadDataDiff struct {
 func (n *EvalReadDataDiff) Eval(ctx EvalContext) (interface{}, error) {
 	// TODO: test
 
+	var diags tfdiags.Diagnostics
+
+	// The provider and hook APIs still expect our legacy InstanceInfo type.
+	legacyInfo := NewInstanceInfo(n.Addr.Absolute(ctx.Path()).ContainingResource())
+
 	err := ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PreDiff(n.Info, nil)
+		return h.PreDiff(legacyInfo, nil)
 	})
 	if err != nil {
 		return nil, err
 	}
 
 	var diff *InstanceDiff
+	var configVal cty.Value
 
 	if n.Previous != nil && *n.Previous != nil && (*n.Previous).GetDestroy() {
 		// If we're re-diffing for a diff that was already planning to
@@ -37,11 +52,28 @@ func (n *EvalReadDataDiff) Eval(ctx EvalContext) (interface{}, error) {
 	} else {
 		provider := *n.Provider
 		config := *n.Config
+		providerSchema := *n.ProviderSchema
+		schema := providerSchema.DataSources[n.Addr.Resource.Type]
+		if schema == nil {
+			// Should be caught during validation, so we don't bother with a pretty error here
+			return nil, fmt.Errorf("provider does not support data source %q", n.Addr.Resource.Type)
+		}
+
+		var configDiags tfdiags.Diagnostics
+		configVal, _, configDiags = ctx.EvaluateBlock(config.Config, schema, nil)
+		diags = diags.Append(configDiags)
+		if configDiags.HasErrors() {
+			return nil, diags.Err()
+		}
+
+		// The provider API still expects our legacy ResourceConfig type.
+		legacyRC := NewResourceConfigShimmed(configVal, schema)
 
 		var err error
-		diff, err = provider.ReadDataDiff(n.Info, config)
+		diff, err = provider.ReadDataDiff(legacyInfo, legacyRC)
 		if err != nil {
-			return nil, err
+			diags = diags.Append(err)
+			return nil, diags.Err()
 		}
 		if diff == nil {
 			diff = new(InstanceDiff)
@@ -61,7 +93,7 @@ func (n *EvalReadDataDiff) Eval(ctx EvalContext) (interface{}, error) {
 	}
 
 	err = ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PostDiff(n.Info, diff)
+		return h.PostDiff(legacyInfo, diff)
 	})
 	if err != nil {
 		return nil, err
@@ -69,6 +101,10 @@ func (n *EvalReadDataDiff) Eval(ctx EvalContext) (interface{}, error) {
 
 	*n.Output = diff
 
+	if n.OutputValue != nil {
+		*n.OutputValue = configVal
+	}
+
 	if n.OutputState != nil {
 		state := &InstanceState{}
 		*n.OutputState = state
@@ -80,16 +116,16 @@ func (n *EvalReadDataDiff) Eval(ctx EvalContext) (interface{}, error) {
 		}
 	}
 
-	return nil, nil
+	return nil, diags.ErrWithWarnings()
 }
 
 // EvalReadDataApply is an EvalNode implementation that executes a data
 // resource's ReadDataApply method to read data from the data source.
 type EvalReadDataApply struct {
+	Addr     addrs.ResourceInstance
 	Provider *ResourceProvider
 	Output   **InstanceState
 	Diff     **InstanceDiff
-	Info     *InstanceInfo
 }
 
 func (n *EvalReadDataApply) Eval(ctx EvalContext) (interface{}, error) {
@@ -97,6 +133,9 @@ func (n *EvalReadDataApply) Eval(ctx EvalContext) (interface{}, error) {
 	provider := *n.Provider
 	diff := *n.Diff
 
+	// The provider and hook APIs still expect our legacy InstanceInfo type.
+	legacyInfo := NewInstanceInfo(n.Addr.Absolute(ctx.Path()).ContainingResource())
+
 	// If the diff is for *destroying* this resource then we'll
 	// just drop its state and move on, since data resources don't
 	// support an actual "destroy" action.
@@ -113,19 +152,19 @@ func (n *EvalReadDataApply) Eval(ctx EvalContext) (interface{}, error) {
 	err := ctx.Hook(func(h Hook) (HookAction, error) {
 		// We don't have a state yet, so we'll just give the hook an
 		// empty one to work with.
-		return h.PreRefresh(n.Info, &InstanceState{})
+		return h.PreRefresh(legacyInfo, &InstanceState{})
 	})
 	if err != nil {
 		return nil, err
 	}
 
-	state, err := provider.ReadDataApply(n.Info, diff)
+	state, err := provider.ReadDataApply(legacyInfo, diff)
 	if err != nil {
-		return nil, fmt.Errorf("%s: %s", n.Info.Id, err)
+		return nil, fmt.Errorf("%s: %s", n.Addr.Absolute(ctx.Path()).String(), err)
 	}
 
 	err = ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PostRefresh(n.Info, state)
+		return h.PostRefresh(legacyInfo, state)
 	})
 	if err != nil {
 		return nil, err

terraform/eval_refresh.go

@@ -3,14 +3,16 @@ package terraform
 import (
 	"fmt"
 	"log"
+
+	"github.com/hashicorp/terraform/addrs"
 )
 
 // EvalRefresh is an EvalNode implementation that does a refresh for
 // a resource.
 type EvalRefresh struct {
+	Addr     addrs.ResourceInstance
 	Provider *ResourceProvider
 	State    **InstanceState
-	Info     *InstanceInfo
 	Output   **InstanceState
 }
 
@@ -19,29 +21,32 @@ func (n *EvalRefresh) Eval(ctx EvalContext) (interface{}, error) {
 	provider := *n.Provider
 	state := *n.State
 
+	// The provider and hook APIs still expect our legacy InstanceInfo type.
+	legacyInfo := NewInstanceInfo(n.Addr.Absolute(ctx.Path()).ContainingResource())
+
 	// If we have no state, we don't do any refreshing
 	if state == nil {
-		log.Printf("[DEBUG] refresh: %s: no state, not refreshing", n.Info.Id)
+		log.Printf("[DEBUG] refresh: %s: no state, so not refreshing", n.Addr.Absolute(ctx.Path()))
 		return nil, nil
 	}
 
 	// Call pre-refresh hook
 	err := ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PreRefresh(n.Info, state)
+		return h.PreRefresh(legacyInfo, state)
 	})
 	if err != nil {
 		return nil, err
 	}
 
 	// Refresh!
-	state, err = provider.Refresh(n.Info, state)
+	state, err = provider.Refresh(legacyInfo, state)
 	if err != nil {
-		return nil, fmt.Errorf("%s: %s", n.Info.Id, err.Error())
+		return nil, fmt.Errorf("%s: %s", n.Addr.Absolute(ctx.Path()), err.Error())
 	}
 
 	// Call post-refresh hook
 	err = ctx.Hook(func(h Hook) (HookAction, error) {
-		return h.PostRefresh(n.Info, state)
+		return h.PostRefresh(legacyInfo, state)
 	})
 	if err != nil {
 		return nil, err

terraform/eval_resource.go

@@ -1,13 +0,0 @@
-package terraform
-
-// EvalInstanceInfo is an EvalNode implementation that fills in the
-// InstanceInfo as much as it can.
-type EvalInstanceInfo struct {
-	Info *InstanceInfo
-}
-
-// TODO: test
-func (n *EvalInstanceInfo) Eval(ctx EvalContext) (interface{}, error) {
-	n.Info.ModulePath = ctx.Path()
-	return nil, nil
-}

terraform/eval_state.go

@@ -2,6 +2,8 @@ package terraform
 
 import (
 	"fmt"
+
+	"github.com/hashicorp/terraform/addrs"
 )
 
 // EvalReadState is an EvalNode implementation that reads the
@@ -130,13 +132,13 @@ func (n *EvalUpdateStateHook) Eval(ctx EvalContext) (interface{}, error) {
 type EvalWriteState struct {
 	Name         string
 	ResourceType string
-	Provider     string
+	Provider     addrs.AbsProviderConfig
 	Dependencies []string
 	State        **InstanceState
 }
 
 func (n *EvalWriteState) Eval(ctx EvalContext) (interface{}, error) {
-	return writeInstanceToState(ctx, n.Name, n.ResourceType, n.Provider, n.Dependencies,
+	return writeInstanceToState(ctx, n.Name, n.ResourceType, n.Provider.String(), n.Dependencies,
 		func(rs *ResourceState) error {
 			rs.Primary = *n.State
 			return nil

terraform/eval_validate.go

@@ -3,125 +3,175 @@ package terraform
 import (
 	"fmt"
 
-	"github.com/hashicorp/terraform/config"
-	"github.com/mitchellh/mapstructure"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/config/configschema"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/tfdiags"
+	"github.com/zclconf/go-cty/cty"
+	"github.com/zclconf/go-cty/cty/gocty"
 )
 
-// EvalValidateError is the error structure returned if there were
-// validation errors.
-type EvalValidateError struct {
-	Warnings []string
-	Errors   []error
-}
-
-func (e *EvalValidateError) Error() string {
-	return fmt.Sprintf("Warnings: %s. Errors: %s", e.Warnings, e.Errors)
-}
-
 // EvalValidateCount is an EvalNode implementation that validates
 // the count of a resource.
 type EvalValidateCount struct {
-	Resource *config.Resource
+	Resource *configs.Resource
 }
 
 // TODO: test
 func (n *EvalValidateCount) Eval(ctx EvalContext) (interface{}, error) {
+	var diags tfdiags.Diagnostics
 	var count int
-	var errs []error
 	var err error
-	if _, err := ctx.Interpolate(n.Resource.RawCount, nil); err != nil {
-		errs = append(errs, fmt.Errorf(
-			"Failed to interpolate count: %s", err))
+
+	val, valDiags := ctx.EvaluateExpr(n.Resource.Count, cty.Number, nil)
+	diags = diags.Append(valDiags)
+	if valDiags.HasErrors() {
+		goto RETURN
+	}
+	if val.IsNull() || !val.IsKnown() {
 		goto RETURN
 	}
 
-	count, err = n.Resource.Count()
+	err = gocty.FromCtyValue(val, &count)
 	if err != nil {
-		// If we can't get the count during validation, then
-		// just replace it with the number 1.
-		c := n.Resource.RawCount.Config()
-		c[n.Resource.RawCount.Key] = "1"
-		count = 1
-	}
-	err = nil
-
-	if count < 0 {
-		errs = append(errs, fmt.Errorf(
-			"Count is less than zero: %d", count))
+		// The EvaluateExpr call above already guaranteed us a number value,
+		// so if we end up here then we have something that is out of range
+		// for an int, and the error message will include a description of
+		// the valid range.
+		rawVal := val.AsBigFloat()
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Invalid count value",
+			Detail:   fmt.Sprintf("The number %s is not a valid count value: %s.", rawVal, err),
+			Subject:  n.Resource.Count.Range().Ptr(),
+		})
+	} else if count < 0 {
+		rawVal := val.AsBigFloat()
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Invalid count value",
+			Detail:   fmt.Sprintf("The number %s is not a valid count value: count must not be negative.", rawVal),
+			Subject:  n.Resource.Count.Range().Ptr(),
+		})
 	}
 
 RETURN:
-	if len(errs) != 0 {
-		err = &EvalValidateError{
-			Errors: errs,
-		}
-	}
-	return nil, err
+	return nil, diags.NonFatalErr()
 }
 
 // EvalValidateProvider is an EvalNode implementation that validates
-// the configuration of a resource.
+// a provider configuration.
 type EvalValidateProvider struct {
+	Addr     addrs.ProviderConfig
 	Provider *ResourceProvider
-	Config   **ResourceConfig
+	Config   *configs.Provider
 }
 
 func (n *EvalValidateProvider) Eval(ctx EvalContext) (interface{}, error) {
+	var diags tfdiags.Diagnostics
 	provider := *n.Provider
-	config := *n.Config
+	config := n.Config
 
-	warns, errs := provider.Validate(config)
+	if n.Config == nil {
+		// Nothing to validate, then.
+		return nil, nil
+	}
+
+	schema, err := provider.GetSchema(&ProviderSchemaRequest{})
+	if err != nil {
+		diags = diags.Append(err)
+		return nil, diags.NonFatalErr()
+	}
+
+	configSchema := schema.Provider
+	configBody := buildProviderConfig(ctx, n.Addr, config.Config)
+	configVal, configBody, evalDiags := ctx.EvaluateBlock(configBody, configSchema, nil)
+	diags = diags.Append(evalDiags)
+	if evalDiags.HasErrors() {
+		return nil, diags.NonFatalErr()
+	}
+
+	// The provider API expects our legacy ResourceConfig type, so we'll need
+	// to shim here.
+	rc := NewResourceConfigShimmed(configVal, configSchema)
+
+	warns, errs := provider.Validate(rc)
 	if len(warns) == 0 && len(errs) == 0 {
 		return nil, nil
 	}
 
-	return nil, &EvalValidateError{
-		Warnings: warns,
-		Errors:   errs,
+	// FIXME: Once provider.Validate itself returns diagnostics, just
+	// return diags.NonFatalErr() immediately here.
+	for _, warn := range warns {
+		diags = diags.Append(tfdiags.SimpleWarning(warn))
 	}
+	for _, err := range errs {
+		diags = diags.Append(err)
+	}
+
+	return nil, diags.NonFatalErr()
 }
 
 // EvalValidateProvisioner is an EvalNode implementation that validates
-// the configuration of a resource.
+// the configuration of a provisioner belonging to a resource.
 type EvalValidateProvisioner struct {
-	Provisioner *ResourceProvisioner
-	Config      **ResourceConfig
-	ConnConfig  **ResourceConfig
+	ResourceAddr addrs.ResourceInstance
+	Provisioner  *ResourceProvisioner
+	Schema       **configschema.Block
+	Config       *configs.Provisioner
+	ConnConfig   *configs.Connection
 }
 
 func (n *EvalValidateProvisioner) Eval(ctx EvalContext) (interface{}, error) {
 	provisioner := *n.Provisioner
 	config := *n.Config
+	schema := *n.Schema
+
 	var warns []string
 	var errs []error
 
+	var diags tfdiags.Diagnostics
+
 	{
 		// Validate the provisioner's own config first
-		w, e := provisioner.Validate(config)
+
+		configVal, _, configDiags := ctx.EvaluateBlock(config.Config, schema, n.ResourceAddr)
+		diags = diags.Append(configDiags)
+		if configDiags.HasErrors() {
+			return nil, diags.Err()
+		}
+
+		// The provisioner API still uses our legacy ResourceConfig type, so
+		// we need to shim it.
+		legacyRC := NewResourceConfigShimmed(configVal, schema)
+
+		w, e := provisioner.Validate(legacyRC)
 		warns = append(warns, w...)
 		errs = append(errs, e...)
+
+		// FIXME: Once the provisioner API itself returns diagnostics, just
+		// return diags.NonFatalErr() here.
+		for _, warn := range warns {
+			diags = diags.Append(tfdiags.SimpleWarning(warn))
+		}
+		for _, err := range errs {
+			diags = diags.Append(err)
+		}
 	}
 
 	{
 		// Now validate the connection config, which might either be from
 		// the provisioner block itself or inherited from the resource's
 		// shared connection info.
-		w, e := n.validateConnConfig(*n.ConnConfig)
-		warns = append(warns, w...)
-		errs = append(errs, e...)
+		connDiags := n.validateConnConfig(ctx, n.ConnConfig, n.ResourceAddr)
+		diags = diags.Append(connDiags)
 	}
 
-	if len(warns) == 0 && len(errs) == 0 {
-		return nil, nil
-	}
-
-	return nil, &EvalValidateError{
-		Warnings: warns,
-		Errors:   errs,
-	}
+	return nil, diags.NonFatalErr()
 }
 
-func (n *EvalValidateProvisioner) validateConnConfig(connConfig *ResourceConfig) (warns []string, errs []error) {
+func (n *EvalValidateProvisioner) validateConnConfig(ctx EvalContext, config *configs.Connection, self addrs.Referenceable) tfdiags.Diagnostics {
 	// We can't comprehensively validate the connection config since its
 	// final structure is decided by the communicator and we can't instantiate
 	// that until we have a complete instance state. However, we *can* catch
@@ -129,103 +179,228 @@ func (n *EvalValidateProvisioner) validateConnConfig(connConfig *ResourceConfig)
 	// typos early rather than waiting until we actually try to run one of
 	// the resource's provisioners.
 
-	type connConfigSuperset struct {
-		// All attribute types are interface{} here because at this point we
-		// may still have unresolved interpolation expressions, which will
-		// appear as strings regardless of the final goal type.
+	var diags tfdiags.Diagnostics
 
-		Type       interface{} `mapstructure:"type"`
-		User       interface{} `mapstructure:"user"`
-		Password   interface{} `mapstructure:"password"`
-		Host       interface{} `mapstructure:"host"`
-		Port       interface{} `mapstructure:"port"`
-		Timeout    interface{} `mapstructure:"timeout"`
-		ScriptPath interface{} `mapstructure:"script_path"`
+	// We evaluate here just by evaluating the block and returning any
+	// diagnostics we get, since evaluation alone is enough to check for
+	// extraneous arguments and incorrectly-typed arguments.
+	_, _, configDiags := ctx.EvaluateBlock(config.Config, connectionBlockSupersetSchema, self)
+	diags = diags.Append(configDiags)
+
+	return diags
+}
+
+// connectionBlockSupersetSchema is a schema representing the superset of all
+// possible arguments for "connection" blocks across all supported connection
+// types.
+//
+// This currently lives here because we've not yet updated our communicator
+// subsystem to be aware of schema itself. Once that is done, we can remove
+// this and use a type-specific schema from the communicator to validate
+// exactly what is expected for a given connection type.
+var connectionBlockSupersetSchema = &configschema.Block{
+	Attributes: map[string]*configschema.Attribute{
+		"type": {
+			Type:     cty.String,
+			Required: true,
+		},
+
+		// Common attributes for both connection types
+		"user": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"password": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"host": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"port": {
+			Type:     cty.Number,
+			Required: false,
+		},
+		"timeout": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"script_path": {
+			Type:     cty.String,
+			Required: false,
+		},
 
 		// For type=ssh only (enforced in ssh communicator)
-		PrivateKey        interface{} `mapstructure:"private_key"`
-		HostKey           interface{} `mapstructure:"host_key"`
-		Agent             interface{} `mapstructure:"agent"`
-		BastionHost       interface{} `mapstructure:"bastion_host"`
-		BastionHostKey    interface{} `mapstructure:"bastion_host_key"`
-		BastionPort       interface{} `mapstructure:"bastion_port"`
-		BastionUser       interface{} `mapstructure:"bastion_user"`
-		BastionPassword   interface{} `mapstructure:"bastion_password"`
-		BastionPrivateKey interface{} `mapstructure:"bastion_private_key"`
-		AgentIdentity     interface{} `mapstructure:"agent_identity"`
+		"private_key": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"host_key": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"agent": {
+			Type:     cty.Bool,
+			Required: false,
+		},
+		"agent_identity": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"bastion_host": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"bastion_host_key": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"bastion_port": {
+			Type:     cty.Number,
+			Required: false,
+		},
+		"bastion_user": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"bastion_password": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"bastion_private_key": {
+			Type:     cty.String,
+			Required: false,
+		},
 
 		// For type=winrm only (enforced in winrm communicator)
-		HTTPS    interface{} `mapstructure:"https"`
-		Insecure interface{} `mapstructure:"insecure"`
-		NTLM     interface{} `mapstructure:"use_ntlm"`
-		CACert   interface{} `mapstructure:"cacert"`
-	}
-
-	var metadata mapstructure.Metadata
-	decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
-		Metadata: &metadata,
-		Result:   &connConfigSuperset{}, // result is disregarded; we only care about unused keys
-	})
-	if err != nil {
-		// should never happen
-		errs = append(errs, err)
-		return
-	}
-
-	if err := decoder.Decode(connConfig.Config); err != nil {
-		errs = append(errs, err)
-		return
-	}
-
-	for _, attrName := range metadata.Unused {
-		errs = append(errs, fmt.Errorf("unknown 'connection' argument %q", attrName))
-	}
-	return
+		"https": {
+			Type:     cty.Bool,
+			Required: false,
+		},
+		"insecure": {
+			Type:     cty.Bool,
+			Required: false,
+		},
+		"cacert": {
+			Type:     cty.String,
+			Required: false,
+		},
+		"use_ntlm": {
+			Type:     cty.Bool,
+			Required: false,
+		},
+	},
 }
 
 // EvalValidateResource is an EvalNode implementation that validates
 // the configuration of a resource.
 type EvalValidateResource struct {
-	Provider     *ResourceProvider
-	Config       **ResourceConfig
-	ResourceName string
-	ResourceType string
-	ResourceMode config.ResourceMode
+	Addr           addrs.ResourceInstance
+	Provider       *ResourceProvider
+	ProviderSchema **ProviderSchema
+	Config         *configs.Resource
 
 	// IgnoreWarnings means that warnings will not be passed through. This allows
 	// "just-in-time" passes of validation to continue execution through warnings.
 	IgnoreWarnings bool
+
+	// ConfigVal, if non-nil, will be updated with the value resulting from
+	// evaluating the given configuration body. Since validation is performed
+	// very early, this value is likely to contain lots of unknown values,
+	// but its type will conform to the schema of the resource type associated
+	// with the resource instance being validated.
+	ConfigVal *cty.Value
 }
 
 func (n *EvalValidateResource) Eval(ctx EvalContext) (interface{}, error) {
+	var diags tfdiags.Diagnostics
 	provider := *n.Provider
 	cfg := *n.Config
+	schema := *n.ProviderSchema
+	mode := cfg.Mode
+
 	var warns []string
 	var errs []error
+
 	// Provider entry point varies depending on resource mode, because
 	// managed resources and data resources are two distinct concepts
 	// in the provider abstraction.
-	switch n.ResourceMode {
-	case config.ManagedResourceMode:
-		warns, errs = provider.ValidateResource(n.ResourceType, cfg)
-	case config.DataResourceMode:
-		warns, errs = provider.ValidateDataSource(n.ResourceType, cfg)
+	switch mode {
+	case addrs.ManagedResourceMode:
+		schema, exists := schema.ResourceTypes[cfg.Type]
+		if !exists {
+			diags = diags.Append(&hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Summary:  "Invalid resource type",
+				Detail:   fmt.Sprintf("The provider %s does not support resource type %q.", cfg.ProviderConfigAddr(), cfg.Type),
+				Subject:  &cfg.TypeRange,
+			})
+			return nil, diags.Err()
+		}
+
+		configVal, _, valDiags := ctx.EvaluateBlock(cfg.Config, schema, nil)
+		diags = diags.Append(valDiags)
+		if valDiags.HasErrors() {
+			return nil, diags.Err()
+		}
+
+		// The provider API still expects our legacy types, so we must do some
+		// shimming here.
+		legacyCfg := NewResourceConfigShimmed(configVal, schema)
+		warns, errs = provider.ValidateResource(cfg.Type, legacyCfg)
+
+		if n.ConfigVal != nil {
+			*n.ConfigVal = configVal
+		}
+
+	case addrs.DataResourceMode:
+		schema, exists := schema.DataSources[cfg.Type]
+		if !exists {
+			diags = diags.Append(&hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Summary:  "Invalid data source",
+				Detail:   fmt.Sprintf("The provider %s does not support data source %q.", cfg.ProviderConfigAddr(), cfg.Type),
+				Subject:  &cfg.TypeRange,
+			})
+			return nil, diags.Err()
+		}
+
+		configVal, _, valDiags := ctx.EvaluateBlock(cfg.Config, schema, nil)
+		diags = diags.Append(valDiags)
+		if valDiags.HasErrors() {
+			return nil, diags.Err()
+		}
+
+		// The provider API still expects our legacy types, so we must do some
+		// shimming here.
+		legacyCfg := NewResourceConfigShimmed(configVal, schema)
+		warns, errs = provider.ValidateDataSource(cfg.Type, legacyCfg)
+
+		if n.ConfigVal != nil {
+			*n.ConfigVal = configVal
+		}
 	}
 
-	// If the resource name doesn't match the name regular
-	// expression, show an error.
-	if !config.NameRegexp.Match([]byte(n.ResourceName)) {
-		errs = append(errs, fmt.Errorf(
-			"%s: resource name can only contain letters, numbers, "+
-				"dashes, and underscores.", n.ResourceName))
+	// FIXME: Update the provider API to actually return diagnostics here,
+	// and then we can remove all this shimming and use its diagnostics
+	// directly.
+	for _, warn := range warns {
+		diags = diags.Append(tfdiags.SimpleWarning(warn))
+	}
+	for _, err := range errs {
+		diags = diags.Append(err)
 	}
 
-	if (len(warns) == 0 || n.IgnoreWarnings) && len(errs) == 0 {
+	if n.IgnoreWarnings {
+		// If we _only_ have warnings then we'll return nil.
+		if diags.HasErrors() {
+			return nil, diags.NonFatalErr()
+		}
 		return nil, nil
-	}
-
-	return nil, &EvalValidateError{
-		Warnings: warns,
-		Errors:   errs,
+	} else {
+		// We'll return an error if there are any diagnostics at all, even if
+		// some of them are warnings.
+		return nil, diags.NonFatalErr()
 	}
 }

terraform/eval_validate_selfref.go

@@ -3,72 +3,41 @@ package terraform
 import (
 	"fmt"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/tfdiags"
+
+	"github.com/hashicorp/terraform/lang"
+
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/config/configschema"
 )
 
-// EvalValidateResourceSelfRef is an EvalNode implementation that validates that
-// a configuration doesn't contain a reference to the resource itself.
-//
-// This must be done prior to interpolating configuration in order to avoid
-// any infinite loop scenarios.
-type EvalValidateResourceSelfRef struct {
-	Addr   **ResourceAddress
-	Config **config.RawConfig
+// EvalValidateSelfRef is an EvalNode implementation that checks to ensure that
+// expressions within a particular referencable block do not reference that
+// same block.
+type EvalValidateSelfRef struct {
+	Addr   addrs.Referenceable
+	Config hcl.Body
+	Schema *configschema.Block
 }
 
-func (n *EvalValidateResourceSelfRef) Eval(ctx EvalContext) (interface{}, error) {
-	addr := *n.Addr
-	conf := *n.Config
+func (n *EvalValidateSelfRef) Eval(ctx EvalContext) (interface{}, error) {
+	var diags tfdiags.Diagnostics
+	addr := n.Addr
 
-	// Go through the variables and find self references
-	var errs []error
-	for k, raw := range conf.Variables {
-		rv, ok := raw.(*config.ResourceVariable)
-		if !ok {
-			continue
-		}
+	addrStr := addr.String()
 
-		// Build an address from the variable
-		varAddr := &ResourceAddress{
-			Path:         addr.Path,
-			Mode:         rv.Mode,
-			Type:         rv.Type,
-			Name:         rv.Name,
-			Index:        rv.Index,
-			InstanceType: TypePrimary,
-		}
-
-		// If the variable access is a multi-access (*), then we just
-		// match the index so that we'll match our own addr if everything
-		// else matches.
-		if rv.Multi && rv.Index == -1 {
-			varAddr.Index = addr.Index
-		}
-
-		// This is a weird thing where ResourceAddres has index "-1" when
-		// index isn't set at all. This means index "0" for resource access.
-		// So, if we have this scenario, just set our varAddr to -1 so it
-		// matches.
-		if addr.Index == -1 && varAddr.Index == 0 {
-			varAddr.Index = -1
-		}
-
-		// If the addresses match, then this is a self reference
-		if varAddr.Equals(addr) && varAddr.Index == addr.Index {
-			errs = append(errs, fmt.Errorf(
-				"%s: self reference not allowed: %q",
-				addr, k))
+	refs, _ := lang.ReferencesInBlock(n.Config, n.Schema)
+	for _, ref := range refs {
+		if ref.Subject.String() == addrStr {
+			diags = diags.Append(&hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Summary:  "Self-referential block",
+				Detail:   fmt.Sprintf("Configuration for %s may not refer to itself.", addrStr),
+				Subject:  ref.SourceRange.ToHCL().Ptr(),
+			})
 		}
 	}
 
-	// If no errors, no errors!
-	if len(errs) == 0 {
-		return nil, nil
-	}
-
-	// Wrap the errors in the proper wrapper so we can handle validation
-	// formatting properly upstream.
-	return nil, &EvalValidateError{
-		Errors: errs,
-	}
+	return nil, diags.NonFatalErr()
 }

terraform/eval_variable.go

@@ -4,12 +4,17 @@ import (
 	"fmt"
 	"log"
 	"reflect"
-	"strconv"
 	"strings"
 
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/configs"
+
+	"github.com/hashicorp/terraform/addrs"
+
 	"github.com/hashicorp/terraform/config"
 	"github.com/hashicorp/terraform/config/module"
-	"github.com/hashicorp/terraform/helper/hilmapstructure"
+	"github.com/zclconf/go-cty/cty"
+	"github.com/zclconf/go-cty/cty/convert"
 )
 
 // EvalTypeCheckVariable is an EvalNode which ensures that the variable
@@ -93,166 +98,88 @@ func (n *EvalTypeCheckVariable) Eval(ctx EvalContext) (interface{}, error) {
 	return nil, nil
 }
 
-// EvalSetVariables is an EvalNode implementation that sets the variables
-// explicitly for interpolation later.
-type EvalSetVariables struct {
-	Module    *string
-	Variables map[string]interface{}
+// EvalSetModuleCallArguments is an EvalNode implementation that sets values
+// for arguments of a child module call, for later retrieval during
+// expression evaluation.
+type EvalSetModuleCallArguments struct {
+	Module addrs.ModuleCallInstance
+	Values map[string]cty.Value
 }
 
 // TODO: test
-func (n *EvalSetVariables) Eval(ctx EvalContext) (interface{}, error) {
-	ctx.SetVariables(*n.Module, n.Variables)
+func (n *EvalSetModuleCallArguments) Eval(ctx EvalContext) (interface{}, error) {
+	ctx.SetModuleCallArguments(n.Module, n.Values)
 	return nil, nil
 }
 
-// EvalVariableBlock is an EvalNode implementation that evaluates the
-// given configuration, and uses the final values as a way to set the
-// mapping.
-type EvalVariableBlock struct {
-	Config         **ResourceConfig
-	VariableValues map[string]interface{}
-}
-
-func (n *EvalVariableBlock) Eval(ctx EvalContext) (interface{}, error) {
-	// Clear out the existing mapping
-	for k, _ := range n.VariableValues {
-		delete(n.VariableValues, k)
-	}
-
-	// Get our configuration
-	rc := *n.Config
-	for k, v := range rc.Config {
-		vKind := reflect.ValueOf(v).Type().Kind()
-
-		switch vKind {
-		case reflect.Slice:
-			var vSlice []interface{}
-			if err := hilmapstructure.WeakDecode(v, &vSlice); err == nil {
-				n.VariableValues[k] = vSlice
-				continue
-			}
-		case reflect.Map:
-			var vMap map[string]interface{}
-			if err := hilmapstructure.WeakDecode(v, &vMap); err == nil {
-				n.VariableValues[k] = vMap
-				continue
-			}
-		default:
-			var vString string
-			if err := hilmapstructure.WeakDecode(v, &vString); err == nil {
-				n.VariableValues[k] = vString
-				continue
-			}
-		}
-
-		return nil, fmt.Errorf("Variable value for %s is not a string, list or map type", k)
-	}
-
-	for _, path := range rc.ComputedKeys {
-		log.Printf("[DEBUG] Setting Unknown Variable Value for computed key: %s", path)
-		err := n.setUnknownVariableValueForPath(path)
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	return nil, nil
-}
-
-func (n *EvalVariableBlock) setUnknownVariableValueForPath(path string) error {
-	pathComponents := strings.Split(path, ".")
-
-	if len(pathComponents) < 1 {
-		return fmt.Errorf("No path comoponents in %s", path)
-	}
-
-	if len(pathComponents) == 1 {
-		// Special case the "top level" since we know the type
-		if _, ok := n.VariableValues[pathComponents[0]]; !ok {
-			n.VariableValues[pathComponents[0]] = config.UnknownVariableValue
-		}
-		return nil
-	}
-
-	// Otherwise find the correct point in the tree and then set to unknown
-	var current interface{} = n.VariableValues[pathComponents[0]]
-	for i := 1; i < len(pathComponents); i++ {
-		switch tCurrent := current.(type) {
-		case []interface{}:
-			index, err := strconv.Atoi(pathComponents[i])
-			if err != nil {
-				return fmt.Errorf("Cannot convert %s to slice index in path %s",
-					pathComponents[i], path)
-			}
-			current = tCurrent[index]
-		case []map[string]interface{}:
-			index, err := strconv.Atoi(pathComponents[i])
-			if err != nil {
-				return fmt.Errorf("Cannot convert %s to slice index in path %s",
-					pathComponents[i], path)
-			}
-			current = tCurrent[index]
-		case map[string]interface{}:
-			if val, hasVal := tCurrent[pathComponents[i]]; hasVal {
-				current = val
-				continue
-			}
-
-			tCurrent[pathComponents[i]] = config.UnknownVariableValue
-			break
-		}
-	}
-
-	return nil
-}
-
-// EvalCoerceMapVariable is an EvalNode implementation that recognizes a
-// specific ambiguous HCL parsing situation and resolves it. In HCL parsing, a
-// bare map literal is indistinguishable from a list of maps w/ one element.
+// EvalModuleCallArgument is an EvalNode implementation that produces the value
+// for a particular variable as will be used by a child module instance.
 //
-// We take all the same inputs as EvalTypeCheckVariable above, since we need
-// both the target type and the proposed value in order to properly coerce.
-type EvalCoerceMapVariable struct {
-	Variables  map[string]interface{}
-	ModulePath []string
-	ModuleTree *module.Tree
+// The result is written into the map given in Values, with its key
+// set to the local name of the variable, disregarding the module instance
+// address. Any existing values in that map are deleted first. This weird
+// interface is a result of trying to be convenient for use with
+// EvalContext.SetModuleCallArguments, which expects a map to merge in with
+// any existing arguments.
+type EvalModuleCallArgument struct {
+	Addr   addrs.InputVariable
+	Config *configs.Variable
+	Expr   hcl.Expression
+
+	// If this flag is set, any diagnostics are discarded and this operation
+	// will always succeed, though may produce an unknown value in the
+	// event of an error.
+	IgnoreDiagnostics bool
+
+	Values map[string]cty.Value
 }
 
-// Eval implements the EvalNode interface. See EvalCoerceMapVariable for
-// details.
-func (n *EvalCoerceMapVariable) Eval(ctx EvalContext) (interface{}, error) {
-	currentTree := n.ModuleTree
-	for _, pathComponent := range n.ModulePath[1:] {
-		currentTree = currentTree.Children()[pathComponent]
-	}
-	targetConfig := currentTree.Config()
-
-	prototypes := make(map[string]config.VariableType)
-	for _, variable := range targetConfig.Variables {
-		prototypes[variable.Name] = variable.Type()
+func (n *EvalModuleCallArgument) Eval(ctx EvalContext) (interface{}, error) {
+	// Clear out the existing mapping
+	for k := range n.Values {
+		delete(n.Values, k)
 	}
 
-	for name, declaredType := range prototypes {
-		if declaredType != config.VariableTypeMap {
-			continue
-		}
+	wantType := n.Config.Type
+	name := n.Addr.Name
+	expr := n.Expr
 
-		proposedValue, ok := n.Variables[name]
-		if !ok {
-			continue
-		}
-
-		if list, ok := proposedValue.([]interface{}); ok && len(list) == 1 {
-			if m, ok := list[0].(map[string]interface{}); ok {
-				log.Printf("[DEBUG] EvalCoerceMapVariable: "+
-					"Coercing single element list into map: %#v", m)
-				n.Variables[name] = m
-			}
-		}
+	if expr == nil {
+		// Should never happen, but we'll bail out early here rather than
+		// crash in case it does. We set no value at all in this case,
+		// making a subsequent call to EvalContext.SetModuleCallArguments
+		// a no-op.
+		log.Printf("[ERROR] attempt to evaluate %s with nil expression", n.Addr.String())
+		return nil, nil
 	}
 
-	return nil, nil
+	val, diags := ctx.EvaluateExpr(expr, cty.DynamicPseudoType, nil)
+
+	// We intentionally passed DynamicPseudoType to EvaluateExpr above because
+	// now we can do our own local type conversion and produce an error message
+	// with better context if it fails.
+	var convErr error
+	val, convErr = convert.Convert(val, wantType)
+	if convErr != nil {
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Invalid value for module argument",
+			Detail: fmt.Sprintf(
+				"The given value is not suitable for child module variable %q defined at %s: %s.",
+				name, n.Config.DeclRange.String(), convErr,
+			),
+			Subject: expr.Range().Ptr(),
+		})
+		// We'll return a placeholder unknown value to avoid producing
+		// redundant downstream errors.
+		val = cty.UnknownVal(wantType)
+	}
+
+	n.Values[name] = val
+	if n.IgnoreDiagnostics {
+		return nil, nil
+	}
+	return nil, diags.ErrWithWarnings()
 }
 
 // hclTypeName returns the name of the type that would represent this value in

terraform/evaltree_provider.go

@@ -1,23 +1,22 @@
 package terraform
 
 import (
-	"strings"
-
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
 )
 
 // ProviderEvalTree returns the evaluation tree for initializing and
 // configuring providers.
-func ProviderEvalTree(n *NodeApplyableProvider, config *config.ProviderConfig) EvalNode {
+func ProviderEvalTree(n *NodeApplyableProvider, config *configs.Provider) EvalNode {
 	var provider ResourceProvider
-	var resourceConfig *ResourceConfig
 
-	typeName := strings.SplitN(n.NameValue, ".", 2)[0]
+	addr := n.Addr
+	relAddr := addr.ProviderConfig
 
 	seq := make([]EvalNode, 0, 5)
 	seq = append(seq, &EvalInitProvider{
-		TypeName: typeName,
-		Name:     n.Name(),
+		TypeName: relAddr.Type,
+		Addr:     addr.ProviderConfig,
 	})
 
 	// Input stuff
@@ -26,22 +25,13 @@ func ProviderEvalTree(n *NodeApplyableProvider, config *config.ProviderConfig) E
 		Node: &EvalSequence{
 			Nodes: []EvalNode{
 				&EvalGetProvider{
-					Name:   n.Name(),
+					Addr:   addr,
 					Output: &provider,
 				},
-				&EvalInterpolateProvider{
-					Config: config,
-					Output: &resourceConfig,
-				},
-				&EvalBuildProviderConfig{
-					Provider: n.NameValue,
-					Config:   &resourceConfig,
-					Output:   &resourceConfig,
-				},
 				&EvalInputProvider{
-					Name:     n.NameValue,
+					Addr:     relAddr,
 					Provider: &provider,
-					Config:   &resourceConfig,
+					Config:   config,
 				},
 			},
 		},
@@ -52,21 +42,13 @@ func ProviderEvalTree(n *NodeApplyableProvider, config *config.ProviderConfig) E
 		Node: &EvalSequence{
 			Nodes: []EvalNode{
 				&EvalGetProvider{
-					Name:   n.Name(),
+					Addr:   addr,
 					Output: &provider,
 				},
-				&EvalInterpolateProvider{
-					Config: config,
-					Output: &resourceConfig,
-				},
-				&EvalBuildProviderConfig{
-					Provider: n.NameValue,
-					Config:   &resourceConfig,
-					Output:   &resourceConfig,
-				},
 				&EvalValidateProvider{
+					Addr:     relAddr,
 					Provider: &provider,
-					Config:   &resourceConfig,
+					Config:   config,
 				},
 			},
 		},
@@ -78,18 +60,9 @@ func ProviderEvalTree(n *NodeApplyableProvider, config *config.ProviderConfig) E
 		Node: &EvalSequence{
 			Nodes: []EvalNode{
 				&EvalGetProvider{
-					Name:   n.Name(),
+					Addr:   addr,
 					Output: &provider,
 				},
-				&EvalInterpolateProvider{
-					Config: config,
-					Output: &resourceConfig,
-				},
-				&EvalBuildProviderConfig{
-					Provider: n.NameValue,
-					Config:   &resourceConfig,
-					Output:   &resourceConfig,
-				},
 			},
 		},
 	})
@@ -101,8 +74,9 @@ func ProviderEvalTree(n *NodeApplyableProvider, config *config.ProviderConfig) E
 		Node: &EvalSequence{
 			Nodes: []EvalNode{
 				&EvalConfigProvider{
-					Provider: n.Name(),
-					Config:   &resourceConfig,
+					Addr:     relAddr,
+					Provider: &provider,
+					Config:   config,
 				},
 			},
 		},
@@ -113,6 +87,6 @@ func ProviderEvalTree(n *NodeApplyableProvider, config *config.ProviderConfig) E
 
 // CloseProviderEvalTree returns the evaluation tree for closing
 // provider connections that aren't needed anymore.
-func CloseProviderEvalTree(n string) EvalNode {
-	return &EvalCloseProvider{Name: n}
+func CloseProviderEvalTree(addr addrs.AbsProviderConfig) EvalNode {
+	return &EvalCloseProvider{Addr: addr.ProviderConfig}
 }

terraform/evaluate.go

@@ -0,0 +1,100 @@
+package terraform
+
+import (
+	"sync"
+
+	"github.com/hashicorp/terraform/tfdiags"
+	"github.com/zclconf/go-cty/cty"
+
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/lang"
+)
+
+// Evaluator provides the necessary contextual data for evaluating expressions
+// for a particular walk operation.
+type Evaluator struct {
+	// Operation defines what type of operation this evaluator is being used
+	// for.
+	Operation walkOperation
+
+	// Meta is contextual metadata about the current operation.
+	Meta *ContextMeta
+
+	// Config is the root node in the configuration tree.
+	Config *configs.Config
+
+	// RootVariableValues is a map of values for variables defined in the
+	// root module, passed in from external sources. This must not be
+	// modified during evaluation.
+	RootVariableValues map[string]*InputValue
+
+	// State is the current state. During some operations this structure
+	// is mutated concurrently, and so it must be accessed only while holding
+	// StateLock.
+	State     *State
+	StateLock *sync.RWMutex
+}
+
+// Scope creates an evaluation scope for the given module path and optional
+// resource.
+//
+// If the "self" argument is nil then the "self" object is not available
+// in evaluated expressions. Otherwise, it behaves as an alias for the given
+// address.
+func (e *Evaluator) Scope(modulePath addrs.ModuleInstance, self addrs.Referenceable) *lang.Scope {
+	return &lang.Scope{
+		Data: &evaluationStateData{
+			Evaluator:  e,
+			ModulePath: modulePath,
+		},
+		SelfAddr: self,
+		PureOnly: e.Operation != walkApply && e.Operation != walkDestroy,
+		BaseDir:  ".", // Always current working directory for now.
+	}
+}
+
+// evaluationStateData is an implementation of lang.Data that resolves
+// references primarily (but not exclusively) using information from a State.
+type evaluationStateData struct {
+	Evaluator *Evaluator
+
+	// ModulePath is the path through the dynamic module tree to the module
+	// that references will be resolved relative to.
+	ModulePath addrs.ModuleInstance
+}
+
+// evaluationStateData must implement lang.Data
+var _ lang.Data = (*evaluationStateData)(nil)
+
+func (d *evaluationStateData) GetCountAttr(addrs.CountAttr, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	panic("not yet implemented")
+}
+
+func (d *evaluationStateData) GetInputVariable(addrs.InputVariable, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	panic("not yet implemented")
+}
+
+func (d *evaluationStateData) GetLocalValue(addrs.LocalValue, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	panic("not yet implemented")
+}
+
+func (d *evaluationStateData) GetModuleInstance(addrs.ModuleCallInstance, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	panic("not yet implemented")
+}
+
+func (d *evaluationStateData) GetModuleInstanceOutput(addrs.ModuleCallOutput, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	panic("not yet implemented")
+}
+
+func (d *evaluationStateData) GetPathAttr(addrs.PathAttr, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	panic("not yet implemented")
+}
+
+func (d *evaluationStateData) GetResourceInstance(addrs.ResourceInstance, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	panic("not yet implemented")
+}
+
+func (d *evaluationStateData) GetTerraformAttr(addrs.TerraformAttr, tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	panic("not yet implemented")
+}

terraform/graph.go

@@ -4,17 +4,14 @@ import (
 	"fmt"
 	"log"
 	"runtime/debug"
-	"strings"
+
+	"github.com/hashicorp/terraform/tfdiags"
+
+	"github.com/hashicorp/terraform/addrs"
 
 	"github.com/hashicorp/terraform/dag"
 )
 
-// RootModuleName is the name given to the root module implicitly.
-const RootModuleName = "root"
-
-// RootModulePath is the path for the root module.
-var RootModulePath = []string{RootModuleName}
-
 // Graph represents the graph that Terraform uses to represent resources
 // and their dependencies.
 type Graph struct {
@@ -23,9 +20,7 @@ type Graph struct {
 	dag.AcyclicGraph
 
 	// Path is the path in the module tree that this Graph represents.
-	// The root is represented by a single element list containing
-	// RootModuleName
-	Path []string
+	Path addrs.ModuleInstance
 
 	// debugName is a name for reference in the debug output. This is usually
 	// to indicate what topmost builder was, and if this graph is a shadow or
@@ -40,17 +35,17 @@ func (g *Graph) DirectedGraph() dag.Grapher {
 // Walk walks the graph with the given walker for callbacks. The graph
 // will be walked with full parallelism, so the walker should expect
 // to be called in concurrently.
-func (g *Graph) Walk(walker GraphWalker) error {
+func (g *Graph) Walk(walker GraphWalker) tfdiags.Diagnostics {
 	return g.walk(walker)
 }
 
-func (g *Graph) walk(walker GraphWalker) error {
+func (g *Graph) walk(walker GraphWalker) tfdiags.Diagnostics {
 	// The callbacks for enter/exiting a graph
 	ctx := walker.EnterPath(g.Path)
 	defer walker.ExitPath(g.Path)
 
 	// Get the path for logs
-	path := strings.Join(ctx.Path(), ".")
+	path := ctx.Path().String()
 
 	// Determine if our walker is a panic wrapper
 	panicwrap, ok := walker.(GraphWalkerPanicwrapper)
@@ -69,14 +64,16 @@ func (g *Graph) walk(walker GraphWalker) error {
 
 	// Walk the graph.
 	var walkFn dag.WalkFunc
-	walkFn = func(v dag.Vertex) (rerr error) {
-		log.Printf("[TRACE] vertex '%s.%s': walking", path, dag.VertexName(v))
+	walkFn = func(v dag.Vertex) (diags tfdiags.Diagnostics) {
+		log.Printf("[TRACE] vertex %q: starting visit (%T)", dag.VertexName(v), v)
 		g.DebugVisitInfo(v, g.debugName)
 
 		// If we have a panic wrap GraphWalker and a panic occurs, recover
 		// and call that. We ensure the return value is an error, however,
 		// so that future nodes are not called.
 		defer func() {
+			log.Printf("[TRACE] vertex %q: visit complete", dag.VertexName(v))
+
 			// If no panicwrap, do nothing
 			if panicwrap == nil {
 				return
@@ -89,22 +86,21 @@ func (g *Graph) walk(walker GraphWalker) error {
 			}
 
 			// Modify the return value to show the error
-			rerr = fmt.Errorf("vertex %q captured panic: %s\n\n%s",
-				dag.VertexName(v), err, debug.Stack())
+			diags = diags.Append(fmt.Errorf("vertex %q captured panic: %s\n\n%s", dag.VertexName(v), err, debug.Stack()))
 
 			// Call the panic wrapper
 			panicwrap.Panic(v, err)
 		}()
 
 		walker.EnterVertex(v)
-		defer walker.ExitVertex(v, rerr)
+		defer walker.ExitVertex(v, diags)
 
 		// vertexCtx is the context that we use when evaluating. This
 		// is normally the context of our graph but can be overridden
 		// with a GraphNodeSubPath impl.
 		vertexCtx := ctx
 		if pn, ok := v.(GraphNodeSubPath); ok && len(pn.Path()) > 0 {
-			vertexCtx = walker.EnterPath(normalizeModulePath(pn.Path()))
+			vertexCtx = walker.EnterPath(pn.Path())
 			defer walker.ExitPath(pn.Path())
 		}
 
@@ -112,60 +108,64 @@ func (g *Graph) walk(walker GraphWalker) error {
 		if ev, ok := v.(GraphNodeEvalable); ok {
 			tree := ev.EvalTree()
 			if tree == nil {
-				panic(fmt.Sprintf(
-					"%s.%s (%T): nil eval tree", path, dag.VertexName(v), v))
+				panic(fmt.Sprintf("%q (%T): nil eval tree", dag.VertexName(v), v))
 			}
 
 			// Allow the walker to change our tree if needed. Eval,
 			// then callback with the output.
-			log.Printf("[TRACE] vertex '%s.%s': evaluating", path, dag.VertexName(v))
+			log.Printf("[TRACE] vertex %q: evaluating", dag.VertexName(v))
 
 			g.DebugVertexInfo(v, fmt.Sprintf("evaluating %T(%s)", v, path))
 
 			tree = walker.EnterEvalTree(v, tree)
 			output, err := Eval(tree, vertexCtx)
-			if rerr = walker.ExitEvalTree(v, output, err); rerr != nil {
+			diags = diags.Append(walker.ExitEvalTree(v, output, err))
+			if diags.HasErrors() {
 				return
 			}
 		}
 
 		// If the node is dynamically expanded, then expand it
 		if ev, ok := v.(GraphNodeDynamicExpandable); ok {
-			log.Printf(
-				"[TRACE] vertex '%s.%s': expanding/walking dynamic subgraph",
-				path,
-				dag.VertexName(v))
+			log.Printf("[TRACE] vertex %q: expanding dynamic subgraph", dag.VertexName(v))
 
 			g.DebugVertexInfo(v, fmt.Sprintf("expanding %T(%s)", v, path))
 
 			g, err := ev.DynamicExpand(vertexCtx)
 			if err != nil {
-				rerr = err
+				diags = diags.Append(err)
 				return
 			}
 			if g != nil {
 				// Walk the subgraph
-				if rerr = g.walk(walker); rerr != nil {
+				log.Printf("[TRACE] vertex %q: entering dynamic subgraph", dag.VertexName(v))
+				subDiags := g.walk(walker)
+				diags = diags.Append(subDiags)
+				if subDiags.HasErrors() {
+					log.Printf("[TRACE] vertex %q: dynamic subgraph encountered errors", dag.VertexName(v))
 					return
 				}
+				log.Printf("[TRACE] vertex %q: dynamic subgraph completed successfully", dag.VertexName(v))
+			} else {
+				log.Printf("[TRACE] vertex %q: produced no dynamic subgraph", dag.VertexName(v))
 			}
 		}
 
 		// If the node has a subgraph, then walk the subgraph
 		if sn, ok := v.(GraphNodeSubgraph); ok {
-			log.Printf(
-				"[TRACE] vertex '%s.%s': walking subgraph",
-				path,
-				dag.VertexName(v))
+			log.Printf("[TRACE] vertex %q: entering static subgraph", dag.VertexName(v))
 
 			g.DebugVertexInfo(v, fmt.Sprintf("subgraph: %T(%s)", v, path))
 
-			if rerr = sn.Subgraph().(*Graph).walk(walker); rerr != nil {
+			subDiags := sn.Subgraph().(*Graph).walk(walker)
+			if subDiags.HasErrors() {
+				log.Printf("[TRACE] vertex %q: static subgraph encountered errors", dag.VertexName(v))
 				return
 			}
+			log.Printf("[TRACE] vertex %q: static subgraph completed successfully", dag.VertexName(v))
 		}
 
-		return nil
+		return
 	}
 
 	return g.AcyclicGraph.Walk(walkFn)

terraform/graph_builder.go

@@ -4,6 +4,10 @@ import (
 	"fmt"
 	"log"
 	"strings"
+
+	"github.com/hashicorp/terraform/tfdiags"
+
+	"github.com/hashicorp/terraform/addrs"
 )
 
 // GraphBuilder is an interface that can be implemented and used with
@@ -12,7 +16,7 @@ type GraphBuilder interface {
 	// Build builds the graph for the given module path. It is up to
 	// the interface implementation whether this build should expand
 	// the graph or not.
-	Build(path []string) (*Graph, error)
+	Build(addrs.ModuleInstance) (*Graph, tfdiags.Diagnostics)
 }
 
 // BasicGraphBuilder is a GraphBuilder that builds a graph out of a
@@ -25,7 +29,8 @@ type BasicGraphBuilder struct {
 	Name string
 }
 
-func (b *BasicGraphBuilder) Build(path []string) (*Graph, error) {
+func (b *BasicGraphBuilder) Build(path addrs.ModuleInstance) (*Graph, tfdiags.Diagnostics) {
+	var diags tfdiags.Diagnostics
 	g := &Graph{Path: path}
 
 	debugName := "graph.json"
@@ -36,10 +41,12 @@ func (b *BasicGraphBuilder) Build(path []string) (*Graph, error) {
 	g.SetDebugWriter(debugBuf)
 	defer debugBuf.Close()
 
+	var lastStepStr string
 	for _, step := range b.Steps {
 		if step == nil {
 			continue
 		}
+		log.Printf("[TRACE] Executing graph transform %T", step)
 
 		stepName := fmt.Sprintf("%T", step)
 		dot := strings.LastIndex(stepName, ".")
@@ -56,12 +63,20 @@ func (b *BasicGraphBuilder) Build(path []string) (*Graph, error) {
 		}
 		debugOp.End(errMsg)
 
-		log.Printf(
-			"[TRACE] Graph after step %T:\n\n%s",
-			step, g.StringWithNodeTypes())
+		if thisStepStr := g.StringWithNodeTypes(); thisStepStr != lastStepStr {
+			log.Printf("[TRACE] Completed graph transform %T with new graph:\n%s------", step, thisStepStr)
+			lastStepStr = thisStepStr
+		} else {
+			log.Printf("[TRACE] Completed graph transform %T (no changes)", step)
+		}
 
 		if err != nil {
-			return g, err
+			if nf, isNF := err.(tfdiags.NonFatalError); isNF {
+				diags = diags.Append(nf.Diagnostics)
+			} else {
+				diags = diags.Append(err)
+				return g, diags
+			}
 		}
 	}
 
@@ -69,9 +84,10 @@ func (b *BasicGraphBuilder) Build(path []string) (*Graph, error) {
 	if b.Validate {
 		if err := g.Validate(); err != nil {
 			log.Printf("[ERROR] Graph validation failed. Graph:\n\n%s", g.String())
-			return nil, err
+			diags = diags.Append(err)
+			return nil, diags
 		}
 	}
 
-	return g, nil
+	return g, diags
 }

terraform/graph_builder_apply.go

@@ -1,8 +1,10 @@
 package terraform
 
 import (
-	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/dag"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // ApplyGraphBuilder implements GraphBuilder and is responsible for building
@@ -13,8 +15,8 @@ import (
 // that aren't explicitly in the diff. There are other scenarios where the
 // diff can be deviated, so this is just one layer of protection.
 type ApplyGraphBuilder struct {
-	// Module is the root module for the graph to build.
-	Module *module.Tree
+	// Config is the configuration tree that the diff was built from.
+	Config *configs.Config
 
 	// Diff is the diff to apply.
 	Diff *Diff
@@ -32,7 +34,7 @@ type ApplyGraphBuilder struct {
 	// unnecessary outputs aren't included in the apply graph. The plan
 	// builder successfully handles targeting resources. In the future,
 	// outputs should go into the diff so that this is unnecessary.
-	Targets []string
+	Targets []addrs.Targetable
 
 	// DisableReduce, if true, will not reduce the graph. Great for testing.
 	DisableReduce bool
@@ -45,7 +47,7 @@ type ApplyGraphBuilder struct {
 }
 
 // See GraphBuilder
-func (b *ApplyGraphBuilder) Build(path []string) (*Graph, error) {
+func (b *ApplyGraphBuilder) Build(path addrs.ModuleInstance) (*Graph, tfdiags.Diagnostics) {
 	return (&BasicGraphBuilder{
 		Steps:    b.Steps(),
 		Validate: b.Validate,
@@ -62,9 +64,9 @@ func (b *ApplyGraphBuilder) Steps() []GraphTransformer {
 		}
 	}
 
-	concreteResource := func(a *NodeAbstractResource) dag.Vertex {
-		return &NodeApplyableResource{
-			NodeAbstractResource: a,
+	concreteResource := func(a *NodeAbstractResourceInstance) dag.Vertex {
+		return &NodeApplyableResourceInstance{
+			NodeAbstractResourceInstance: a,
 		}
 	}
 
@@ -72,29 +74,26 @@ func (b *ApplyGraphBuilder) Steps() []GraphTransformer {
 		// Creates all the nodes represented in the diff.
 		&DiffTransformer{
 			Concrete: concreteResource,
-
-			Diff:   b.Diff,
-			Module: b.Module,
-			State:  b.State,
+			Diff:     b.Diff,
 		},
 
 		// Create orphan output nodes
-		&OrphanOutputTransformer{Module: b.Module, State: b.State},
+		&OrphanOutputTransformer{Config: b.Config, State: b.State},
 
 		// Attach the configuration to any resources
-		&AttachResourceConfigTransformer{Module: b.Module},
+		&AttachResourceConfigTransformer{Config: b.Config},
 
 		// Attach the state
 		&AttachStateTransformer{State: b.State},
 
 		// add providers
-		TransformProviders(b.Providers, concreteProvider, b.Module),
+		TransformProviders(b.Providers, concreteProvider, b.Config),
 
 		// Destruction ordering
-		&DestroyEdgeTransformer{Module: b.Module, State: b.State},
+		&DestroyEdgeTransformer{Config: b.Config, State: b.State},
 		GraphTransformIf(
 			func() bool { return !b.Destroy },
-			&CBDEdgeTransformer{Module: b.Module, State: b.State},
+			&CBDEdgeTransformer{Config: b.Config, State: b.State},
 		),
 
 		// Provisioner-related transformations
@@ -102,19 +101,19 @@ func (b *ApplyGraphBuilder) Steps() []GraphTransformer {
 		&ProvisionerTransformer{},
 
 		// Add root variables
-		&RootVariableTransformer{Module: b.Module},
+		&RootVariableTransformer{Config: b.Config},
 
 		// Add the local values
-		&LocalTransformer{Module: b.Module},
+		&LocalTransformer{Config: b.Config},
 
 		// Add the outputs
-		&OutputTransformer{Module: b.Module},
+		&OutputTransformer{Config: b.Config},
 
 		// Add module variables
-		&ModuleVariableTransformer{Module: b.Module},
+		&ModuleVariableTransformer{Config: b.Config},
 
 		// Remove modules no longer present in the config
-		&RemovedModuleTransformer{Module: b.Module, State: b.State},
+		&RemovedModuleTransformer{Config: b.Config, State: b.State},
 
 		// Connect references so ordering is correct
 		&ReferenceTransformer{},

terraform/graph_builder_destroy_plan.go

@@ -1,8 +1,10 @@
 package terraform
 
 import (
-	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/dag"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // DestroyPlanGraphBuilder implements GraphBuilder and is responsible for
@@ -11,21 +13,21 @@ import (
 // Planning a pure destroy operation is simple because we can ignore most
 // ordering configuration and simply reverse the state.
 type DestroyPlanGraphBuilder struct {
-	// Module is the root module for the graph to build.
-	Module *module.Tree
+	// Config is the configuration tree to build the plan from.
+	Config *configs.Config
 
 	// State is the current state
 	State *State
 
 	// Targets are resources to target
-	Targets []string
+	Targets []addrs.Targetable
 
 	// Validate will do structural validation of the graph.
 	Validate bool
 }
 
 // See GraphBuilder
-func (b *DestroyPlanGraphBuilder) Build(path []string) (*Graph, error) {
+func (b *DestroyPlanGraphBuilder) Build(path addrs.ModuleInstance) (*Graph, tfdiags.Diagnostics) {
 	return (&BasicGraphBuilder{
 		Steps:    b.Steps(),
 		Validate: b.Validate,
@@ -35,25 +37,25 @@ func (b *DestroyPlanGraphBuilder) Build(path []string) (*Graph, error) {
 
 // See GraphBuilder
 func (b *DestroyPlanGraphBuilder) Steps() []GraphTransformer {
-	concreteResource := func(a *NodeAbstractResource) dag.Vertex {
-		return &NodePlanDestroyableResource{
-			NodeAbstractResource: a,
+	concreteResourceInstance := func(a *NodeAbstractResourceInstance) dag.Vertex {
+		return &NodePlanDestroyableResourceInstance{
+			NodeAbstractResourceInstance: a,
 		}
 	}
 
 	steps := []GraphTransformer{
 		// Creates all the nodes represented in the state.
 		&StateTransformer{
-			Concrete: concreteResource,
+			Concrete: concreteResourceInstance,
 			State:    b.State,
 		},
 
 		// Attach the configuration to any resources
-		&AttachResourceConfigTransformer{Module: b.Module},
+		&AttachResourceConfigTransformer{Config: b.Config},
 
 		// Destruction ordering. We require this only so that
 		// targeting below will prune the correct things.
-		&DestroyEdgeTransformer{Module: b.Module, State: b.State},
+		&DestroyEdgeTransformer{Config: b.Config, State: b.State},
 
 		// Target. Note we don't set "Destroy: true" here since we already
 		// created proper destroy ordering.

terraform/graph_builder_import.go

@@ -1,8 +1,10 @@
 package terraform
 
 import (
-	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/dag"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // ImportGraphBuilder implements GraphBuilder and is responsible for building
@@ -12,15 +14,15 @@ type ImportGraphBuilder struct {
 	// ImportTargets are the list of resources to import.
 	ImportTargets []*ImportTarget
 
-	// Module is the module to add to the graph. See ImportOpts.Module.
-	Module *module.Tree
+	// Module is a configuration to build the graph from. See ImportOpts.Config.
+	Config *configs.Config
 
 	// Providers is the list of providers supported.
 	Providers []string
 }
 
 // Build builds the graph according to the steps returned by Steps.
-func (b *ImportGraphBuilder) Build(path []string) (*Graph, error) {
+func (b *ImportGraphBuilder) Build(path addrs.ModuleInstance) (*Graph, tfdiags.Diagnostics) {
 	return (&BasicGraphBuilder{
 		Steps:    b.Steps(),
 		Validate: true,
@@ -33,9 +35,9 @@ func (b *ImportGraphBuilder) Build(path []string) (*Graph, error) {
 func (b *ImportGraphBuilder) Steps() []GraphTransformer {
 	// Get the module. If we don't have one, we just use an empty tree
 	// so that the transform still works but does nothing.
-	mod := b.Module
-	if mod == nil {
-		mod = module.NewEmptyTree()
+	config := b.Config
+	if config == nil {
+		config = configs.NewEmptyConfig()
 	}
 
 	// Custom factory for creating providers.
@@ -47,12 +49,12 @@ func (b *ImportGraphBuilder) Steps() []GraphTransformer {
 
 	steps := []GraphTransformer{
 		// Create all our resources from the configuration and state
-		&ConfigTransformer{Module: mod},
+		&ConfigTransformer{Config: config},
 
 		// Add the import steps
 		&ImportStateTransformer{Targets: b.ImportTargets},
 
-		TransformProviders(b.Providers, concreteProvider, mod),
+		TransformProviders(b.Providers, concreteProvider, config),
 
 		// This validates that the providers only depend on variables
 		&ImportProviderValidateTransformer{},

terraform/graph_builder_plan.go

@@ -3,7 +3,11 @@ package terraform
 import (
 	"sync"
 
-	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/terraform/tfdiags"
+
+	"github.com/hashicorp/terraform/addrs"
+
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/dag"
 )
 
@@ -19,8 +23,8 @@ import (
 //     create-before-destroy can be completely ignored.
 //
 type PlanGraphBuilder struct {
-	// Module is the root module for the graph to build.
-	Module *module.Tree
+	// Config is the configuration tree to build a plan from.
+	Config *configs.Config
 
 	// State is the current state
 	State *State
@@ -32,7 +36,7 @@ type PlanGraphBuilder struct {
 	Provisioners []string
 
 	// Targets are resources to target
-	Targets []string
+	Targets []addrs.Targetable
 
 	// DisableReduce, if true, will not reduce the graph. Great for testing.
 	DisableReduce bool
@@ -46,13 +50,13 @@ type PlanGraphBuilder struct {
 	CustomConcrete         bool
 	ConcreteProvider       ConcreteProviderNodeFunc
 	ConcreteResource       ConcreteResourceNodeFunc
-	ConcreteResourceOrphan ConcreteResourceNodeFunc
+	ConcreteResourceOrphan ConcreteResourceInstanceNodeFunc
 
 	once sync.Once
 }
 
 // See GraphBuilder
-func (b *PlanGraphBuilder) Build(path []string) (*Graph, error) {
+func (b *PlanGraphBuilder) Build(path addrs.ModuleInstance) (*Graph, tfdiags.Diagnostics) {
 	return (&BasicGraphBuilder{
 		Steps:    b.Steps(),
 		Validate: b.Validate,
@@ -68,38 +72,38 @@ func (b *PlanGraphBuilder) Steps() []GraphTransformer {
 		// Creates all the resources represented in the config
 		&ConfigTransformer{
 			Concrete: b.ConcreteResource,
-			Module:   b.Module,
+			Config:   b.Config,
 		},
 
 		// Add the local values
-		&LocalTransformer{Module: b.Module},
+		&LocalTransformer{Config: b.Config},
 
 		// Add the outputs
-		&OutputTransformer{Module: b.Module},
+		&OutputTransformer{Config: b.Config},
 
 		// Add orphan resources
 		&OrphanResourceTransformer{
 			Concrete: b.ConcreteResourceOrphan,
 			State:    b.State,
-			Module:   b.Module,
+			Config:   b.Config,
 		},
 
 		// Create orphan output nodes
 		&OrphanOutputTransformer{
-			Module: b.Module,
+			Config: b.Config,
 			State:  b.State,
 		},
 
 		// Attach the configuration to any resources
-		&AttachResourceConfigTransformer{Module: b.Module},
+		&AttachResourceConfigTransformer{Config: b.Config},
 
 		// Attach the state
 		&AttachStateTransformer{State: b.State},
 
 		// Add root variables
-		&RootVariableTransformer{Module: b.Module},
+		&RootVariableTransformer{Config: b.Config},
 
-		TransformProviders(b.Providers, b.ConcreteProvider, b.Module),
+		TransformProviders(b.Providers, b.ConcreteProvider, b.Config),
 
 		// Provisioner-related transformations. Only add these if requested.
 		GraphTransformIf(
@@ -112,11 +116,11 @@ func (b *PlanGraphBuilder) Steps() []GraphTransformer {
 
 		// Add module variables
 		&ModuleVariableTransformer{
-			Module: b.Module,
+			Config: b.Config,
 		},
 
 		// Remove modules no longer present in the config
-		&RemovedModuleTransformer{Module: b.Module, State: b.State},
+		&RemovedModuleTransformer{Config: b.Config, State: b.State},
 
 		// Connect so that the references are ready for targeting. We'll
 		// have to connect again later for providers and so on.
@@ -167,15 +171,13 @@ func (b *PlanGraphBuilder) init() {
 
 	b.ConcreteResource = func(a *NodeAbstractResource) dag.Vertex {
 		return &NodePlannableResource{
-			NodeAbstractCountResource: &NodeAbstractCountResource{
-				NodeAbstractResource: a,
-			},
-		}
-	}
-
-	b.ConcreteResourceOrphan = func(a *NodeAbstractResource) dag.Vertex {
-		return &NodePlannableResourceOrphan{
 			NodeAbstractResource: a,
 		}
 	}
+
+	b.ConcreteResourceOrphan = func(a *NodeAbstractResourceInstance) dag.Vertex {
+		return &NodePlannableResourceInstanceOrphan{
+			NodeAbstractResourceInstance: a,
+		}
+	}
 }

terraform/graph_builder_refresh.go

@@ -3,8 +3,10 @@ package terraform
 import (
 	"log"
 
-	"github.com/hashicorp/terraform/config"
-	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/terraform/tfdiags"
+
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/dag"
 )
 
@@ -21,8 +23,8 @@ import (
 //     create-before-destroy can be completely ignored.
 //
 type RefreshGraphBuilder struct {
-	// Module is the root module for the graph to build.
-	Module *module.Tree
+	// Config is the configuration tree.
+	Config *configs.Config
 
 	// State is the current state
 	State *State
@@ -31,7 +33,7 @@ type RefreshGraphBuilder struct {
 	Providers []string
 
 	// Targets are resources to target
-	Targets []string
+	Targets []addrs.Targetable
 
 	// DisableReduce, if true, will not reduce the graph. Great for testing.
 	DisableReduce bool
@@ -41,7 +43,7 @@ type RefreshGraphBuilder struct {
 }
 
 // See GraphBuilder
-func (b *RefreshGraphBuilder) Build(path []string) (*Graph, error) {
+func (b *RefreshGraphBuilder) Build(path addrs.ModuleInstance) (*Graph, tfdiags.Diagnostics) {
 	return (&BasicGraphBuilder{
 		Steps:    b.Steps(),
 		Validate: b.Validate,
@@ -60,23 +62,19 @@ func (b *RefreshGraphBuilder) Steps() []GraphTransformer {
 
 	concreteManagedResource := func(a *NodeAbstractResource) dag.Vertex {
 		return &NodeRefreshableManagedResource{
-			NodeAbstractCountResource: &NodeAbstractCountResource{
-				NodeAbstractResource: a,
-			},
+			NodeAbstractResource: a,
 		}
 	}
 
-	concreteManagedResourceInstance := func(a *NodeAbstractResource) dag.Vertex {
+	concreteManagedResourceInstance := func(a *NodeAbstractResourceInstance) dag.Vertex {
 		return &NodeRefreshableManagedResourceInstance{
-			NodeAbstractResource: a,
+			NodeAbstractResourceInstance: a,
 		}
 	}
 
 	concreteDataResource := func(a *NodeAbstractResource) dag.Vertex {
 		return &NodeRefreshableDataResource{
-			NodeAbstractCountResource: &NodeAbstractCountResource{
-				NodeAbstractResource: a,
-			},
+			NodeAbstractResource: a,
 		}
 	}
 
@@ -88,13 +86,13 @@ func (b *RefreshGraphBuilder) Steps() []GraphTransformer {
 			if b.State.HasResources() {
 				return &ConfigTransformer{
 					Concrete:   concreteManagedResource,
-					Module:     b.Module,
+					Config:     b.Config,
 					Unique:     true,
 					ModeFilter: true,
-					Mode:       config.ManagedResourceMode,
+					Mode:       addrs.ManagedResourceMode,
 				}
 			}
-			log.Println("[TRACE] No managed resources in state during refresh, skipping managed resource transformer")
+			log.Println("[TRACE] No managed resources in state during refresh; skipping managed resource transformer")
 			return nil
 		}(),
 
@@ -102,10 +100,10 @@ func (b *RefreshGraphBuilder) Steps() []GraphTransformer {
 		// add any orphans from scaling in as destroy nodes.
 		&ConfigTransformer{
 			Concrete:   concreteDataResource,
-			Module:     b.Module,
+			Config:     b.Config,
 			Unique:     true,
 			ModeFilter: true,
-			Mode:       config.DataResourceMode,
+			Mode:       addrs.DataResourceMode,
 		},
 
 		// Add any fully-orphaned resources from config (ones that have been
@@ -114,28 +112,28 @@ func (b *RefreshGraphBuilder) Steps() []GraphTransformer {
 		&OrphanResourceTransformer{
 			Concrete: concreteManagedResourceInstance,
 			State:    b.State,
-			Module:   b.Module,
+			Config:   b.Config,
 		},
 
 		// Attach the state
 		&AttachStateTransformer{State: b.State},
 
 		// Attach the configuration to any resources
-		&AttachResourceConfigTransformer{Module: b.Module},
+		&AttachResourceConfigTransformer{Config: b.Config},
 
 		// Add root variables
-		&RootVariableTransformer{Module: b.Module},
+		&RootVariableTransformer{Config: b.Config},
 
-		TransformProviders(b.Providers, concreteProvider, b.Module),
+		TransformProviders(b.Providers, concreteProvider, b.Config),
 
 		// Add the local values
-		&LocalTransformer{Module: b.Module},
+		&LocalTransformer{Config: b.Config},
 
 		// Add the outputs
-		&OutputTransformer{Module: b.Module},
+		&OutputTransformer{Config: b.Config},
 
 		// Add module variables
-		&ModuleVariableTransformer{Module: b.Module},
+		&ModuleVariableTransformer{Config: b.Config},
 
 		// Connect so that the references are ready for targeting. We'll
 		// have to connect again later for providers and so on.

terraform/graph_builder_validate.go

@@ -23,9 +23,7 @@ func ValidateGraphBuilder(p *PlanGraphBuilder) GraphBuilder {
 
 	p.ConcreteResource = func(a *NodeAbstractResource) dag.Vertex {
 		return &NodeValidatableResource{
-			NodeAbstractCountResource: &NodeAbstractCountResource{
-				NodeAbstractResource: a,
-			},
+			NodeAbstractResource: a,
 		}
 	}
 

terraform/graph_interface_subgraph.go

@@ -1,7 +1,11 @@
 package terraform
 
+import (
+	"github.com/hashicorp/terraform/addrs"
+)
+
 // GraphNodeSubPath says that a node is part of a graph with a
 // different path, and the context should be adjusted accordingly.
 type GraphNodeSubPath interface {
-	Path() []string
+	Path() addrs.ModuleInstance
 }

terraform/graph_walk.go

@@ -1,18 +1,20 @@
 package terraform
 
 import (
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/dag"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // GraphWalker is an interface that can be implemented that when used
 // with Graph.Walk will invoke the given callbacks under certain events.
 type GraphWalker interface {
-	EnterPath([]string) EvalContext
-	ExitPath([]string)
+	EnterPath(addrs.ModuleInstance) EvalContext
+	ExitPath(addrs.ModuleInstance)
 	EnterVertex(dag.Vertex)
-	ExitVertex(dag.Vertex, error)
+	ExitVertex(dag.Vertex, tfdiags.Diagnostics)
 	EnterEvalTree(dag.Vertex, EvalNode) EvalNode
-	ExitEvalTree(dag.Vertex, interface{}, error) error
+	ExitEvalTree(dag.Vertex, interface{}, error) tfdiags.Diagnostics
 }
 
 // GrpahWalkerPanicwrapper can be optionally implemented to catch panics
@@ -50,11 +52,11 @@ func (graphWalkerPanicwrapper) Panic(dag.Vertex, interface{}) {}
 // implementing all the required functions.
 type NullGraphWalker struct{}
 
-func (NullGraphWalker) EnterPath([]string) EvalContext                  { return new(MockEvalContext) }
-func (NullGraphWalker) ExitPath([]string)                               {}
+func (NullGraphWalker) EnterPath(addrs.ModuleInstance) EvalContext      { return new(MockEvalContext) }
+func (NullGraphWalker) ExitPath(addrs.ModuleInstance)                   {}
 func (NullGraphWalker) EnterVertex(dag.Vertex)                          {}
-func (NullGraphWalker) ExitVertex(dag.Vertex, error)                    {}
+func (NullGraphWalker) ExitVertex(dag.Vertex, tfdiags.Diagnostics)      {}
 func (NullGraphWalker) EnterEvalTree(v dag.Vertex, n EvalNode) EvalNode { return n }
-func (NullGraphWalker) ExitEvalTree(dag.Vertex, interface{}, error) error {
+func (NullGraphWalker) ExitEvalTree(dag.Vertex, interface{}, error) tfdiags.Diagnostics {
 	return nil
 }

terraform/graph_walk_context.go

@@ -2,11 +2,14 @@ package terraform
 
 import (
 	"context"
-	"fmt"
 	"log"
 	"sync"
 
-	"github.com/hashicorp/errwrap"
+	"github.com/hashicorp/terraform/config/configschema"
+	"github.com/hashicorp/terraform/tfdiags"
+
+	"github.com/hashicorp/terraform/addrs"
+
 	"github.com/hashicorp/terraform/dag"
 )
 
@@ -20,10 +23,9 @@ type ContextGraphWalker struct {
 	Operation   walkOperation
 	StopContext context.Context
 
-	// Outputs, do not set these. Do not read these while the graph
-	// is being walked.
-	ValidationWarnings []string
-	ValidationErrors   []error
+	// This is an output. Do not set this, nor read it while a graph walk
+	// is in progress.
+	NonFatalDiagnostics tfdiags.Diagnostics
 
 	errorLock           sync.Mutex
 	once                sync.Once
@@ -32,19 +34,21 @@ type ContextGraphWalker struct {
 	interpolaterVars    map[string]map[string]interface{}
 	interpolaterVarLock sync.Mutex
 	providerCache       map[string]ResourceProvider
+	providerSchemas     map[string]*ProviderSchema
 	providerLock        sync.Mutex
 	provisionerCache    map[string]ResourceProvisioner
+	provisionerSchemas  map[string]*configschema.Block
 	provisionerLock     sync.Mutex
 }
 
-func (w *ContextGraphWalker) EnterPath(path []string) EvalContext {
+func (w *ContextGraphWalker) EnterPath(path addrs.ModuleInstance) EvalContext {
 	w.once.Do(w.init)
 
 	w.contextLock.Lock()
 	defer w.contextLock.Unlock()
 
 	// If we already have a context for this path cached, use that
-	key := PathCacheKey(path)
+	key := path.String()
 	if ctx, ok := w.contexts[key]; ok {
 		return ctx
 	}
@@ -65,6 +69,13 @@ func (w *ContextGraphWalker) EnterPath(path []string) EvalContext {
 	w.interpolaterVars[key] = variables
 	w.interpolaterVarLock.Unlock()
 
+	// Our evaluator shares some locks with the main context and the walker
+	// so that we can safely run multiple evaluations at once across
+	// different modules.
+	evaluator := &Evaluator{
+		StateLock: &w.Context.stateLock,
+	}
+
 	ctx := &BuiltinEvalContext{
 		StopContext:         w.StopContext,
 		PathValue:           path,
@@ -80,17 +91,7 @@ func (w *ContextGraphWalker) EnterPath(path []string) EvalContext {
 		DiffLock:            &w.Context.diffLock,
 		StateValue:          w.Context.state,
 		StateLock:           &w.Context.stateLock,
-		Interpolater: &Interpolater{
-			Operation:          w.Operation,
-			Meta:               w.Context.meta,
-			Module:             w.Context.module,
-			State:              w.Context.state,
-			StateLock:          &w.Context.stateLock,
-			VariableValues:     variables,
-			VariableValuesLock: &w.interpolaterVarLock,
-		},
-		InterpolaterVars:    w.interpolaterVars,
-		InterpolaterVarLock: &w.interpolaterVarLock,
+		Evaluator:           evaluator,
 	}
 
 	w.contexts[key] = ctx
@@ -98,8 +99,7 @@ func (w *ContextGraphWalker) EnterPath(path []string) EvalContext {
 }
 
 func (w *ContextGraphWalker) EnterEvalTree(v dag.Vertex, n EvalNode) EvalNode {
-	log.Printf("[TRACE] [%s] Entering eval tree: %s",
-		w.Operation, dag.VertexName(v))
+	log.Printf("[TRACE] [%s] Entering eval tree: %s", w.Operation, dag.VertexName(v))
 
 	// Acquire a lock on the semaphore
 	w.Context.parallelSem.Acquire()
@@ -109,10 +109,8 @@ func (w *ContextGraphWalker) EnterEvalTree(v dag.Vertex, n EvalNode) EvalNode {
 	return EvalFilter(n, EvalNodeFilterOp(w.Operation))
 }
 
-func (w *ContextGraphWalker) ExitEvalTree(
-	v dag.Vertex, output interface{}, err error) error {
-	log.Printf("[TRACE] [%s] Exiting eval tree: %s",
-		w.Operation, dag.VertexName(v))
+func (w *ContextGraphWalker) ExitEvalTree(v dag.Vertex, output interface{}, err error) tfdiags.Diagnostics {
+	log.Printf("[TRACE] [%s] Exiting eval tree: %s", w.Operation, dag.VertexName(v))
 
 	// Release the semaphore
 	w.Context.parallelSem.Release()
@@ -125,30 +123,28 @@ func (w *ContextGraphWalker) ExitEvalTree(
 	w.errorLock.Lock()
 	defer w.errorLock.Unlock()
 
-	// Try to get a validation error out of it. If its not a validation
-	// error, then just record the normal error.
-	verr, ok := err.(*EvalValidateError)
-	if !ok {
-		return err
+	// If the error is non-fatal then we'll accumulate its diagnostics in our
+	// non-fatal list, rather than returning it directly, so that the graph
+	// walk can continue.
+	if nferr, ok := err.(tfdiags.NonFatalError); ok {
+		w.NonFatalDiagnostics = w.NonFatalDiagnostics.Append(nferr.Diagnostics)
+		return nil
 	}
 
-	for _, msg := range verr.Warnings {
-		w.ValidationWarnings = append(
-			w.ValidationWarnings,
-			fmt.Sprintf("%s: %s", dag.VertexName(v), msg))
-	}
-	for _, e := range verr.Errors {
-		w.ValidationErrors = append(
-			w.ValidationErrors,
-			errwrap.Wrapf(fmt.Sprintf("%s: {{err}}", dag.VertexName(v)), e))
-	}
-
-	return nil
+	// Otherwise, we'll let our usual diagnostics machinery figure out how to
+	// unpack this as one or more diagnostic messages and return that. If we
+	// get down here then the returned diagnostics will contain at least one
+	// error, causing the graph walk to halt.
+	var diags tfdiags.Diagnostics
+	diags = diags.Append(err)
+	return diags
 }
 
 func (w *ContextGraphWalker) init() {
-	w.contexts = make(map[string]*BuiltinEvalContext, 5)
-	w.providerCache = make(map[string]ResourceProvider, 5)
-	w.provisionerCache = make(map[string]ResourceProvisioner, 5)
-	w.interpolaterVars = make(map[string]map[string]interface{}, 5)
+	w.contexts = make(map[string]*BuiltinEvalContext)
+	w.providerCache = make(map[string]ResourceProvider)
+	w.providerSchemas = make(map[string]*ProviderSchema)
+	w.provisionerCache = make(map[string]ResourceProvisioner)
+	w.provisionerSchemas = make(map[string]*configschema.Block)
+	w.interpolaterVars = make(map[string]map[string]interface{})
 }

terraform/interpolate.go

@@ -45,65 +45,7 @@ type InterpolationScope struct {
 func (i *Interpolater) Values(
 	scope *InterpolationScope,
 	vars map[string]config.InterpolatedVariable) (map[string]ast.Variable, error) {
-	if scope == nil {
-		scope = &InterpolationScope{}
-	}
-
-	result := make(map[string]ast.Variable, len(vars))
-
-	// Copy the default variables
-	if i.Module != nil && scope != nil {
-		mod := i.Module
-		if len(scope.Path) > 1 {
-			mod = i.Module.Child(scope.Path[1:])
-		}
-		for _, v := range mod.Config().Variables {
-			// Set default variables
-			if v.Default == nil {
-				continue
-			}
-
-			n := fmt.Sprintf("var.%s", v.Name)
-			variable, err := hil.InterfaceToVariable(v.Default)
-			if err != nil {
-				return nil, fmt.Errorf("invalid default map value for %s: %v", v.Name, v.Default)
-			}
-
-			result[n] = variable
-		}
-	}
-
-	for n, rawV := range vars {
-		var err error
-		switch v := rawV.(type) {
-		case *config.CountVariable:
-			err = i.valueCountVar(scope, n, v, result)
-		case *config.ModuleVariable:
-			err = i.valueModuleVar(scope, n, v, result)
-		case *config.PathVariable:
-			err = i.valuePathVar(scope, n, v, result)
-		case *config.ResourceVariable:
-			err = i.valueResourceVar(scope, n, v, result)
-		case *config.SelfVariable:
-			err = i.valueSelfVar(scope, n, v, result)
-		case *config.SimpleVariable:
-			err = i.valueSimpleVar(scope, n, v, result)
-		case *config.TerraformVariable:
-			err = i.valueTerraformVar(scope, n, v, result)
-		case *config.LocalVariable:
-			err = i.valueLocalVar(scope, n, v, result)
-		case *config.UserVariable:
-			err = i.valueUserVar(scope, n, v, result)
-		default:
-			err = fmt.Errorf("%s: unknown variable type: %T", n, rawV)
-		}
-
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	return result, nil
+	return nil, fmt.Errorf("type Interpolator is no longer supported; use the evaluator API instead")
 }
 
 func (i *Interpolater) valueCountVar(
@@ -153,7 +95,7 @@ func (i *Interpolater) valueModuleVar(
 	defer i.StateLock.RUnlock()
 
 	// Get the module where we're looking for the value
-	mod := i.State.ModuleByPath(path)
+	mod := i.State.ModuleByPath(normalizeModulePath(path))
 	if mod == nil {
 		// If the module doesn't exist, then we can return an empty string.
 		// This happens usually only in Refresh() when we haven't populated
@@ -365,7 +307,7 @@ func (i *Interpolater) valueLocalVar(
 	}
 
 	// Get the relevant module
-	module := i.State.ModuleByPath(scope.Path)
+	module := i.State.ModuleByPath(normalizeModulePath(scope.Path))
 	if module == nil {
 		result[n] = unknownVariable()
 		return nil
@@ -776,7 +718,7 @@ func (i *Interpolater) resourceVariableInfo(
 	}
 
 	// Get the relevant module
-	module := i.State.ModuleByPath(scope.Path)
+	module := i.State.ModuleByPath(normalizeModulePath(scope.Path))
 	return module, cr, nil
 }
 

terraform/module_dependencies.go

@@ -101,15 +101,15 @@ func configTreeConfigDependencies(root *configs.Config, inheritProviders map[str
 		// dependency, though we'll only record it if there isn't already
 		// an explicit dependency on the same provider.
 		for _, rc := range module.ManagedResources {
-			fullName := rc.ProviderConfigKey()
-			inst := moduledeps.ProviderInstance(fullName)
+			addr := rc.ProviderConfigAddr()
+			inst := moduledeps.ProviderInstance(addr.StringCompact())
 			if _, exists := providers[inst]; exists {
 				// Explicit dependency already present
 				continue
 			}
 
 			reason := moduledeps.ProviderDependencyImplicit
-			if _, inherited := inheritProviders[fullName]; inherited {
+			if _, inherited := inheritProviders[addr.String()]; inherited {
 				reason = moduledeps.ProviderDependencyInherited
 			}
 
@@ -119,15 +119,15 @@ func configTreeConfigDependencies(root *configs.Config, inheritProviders map[str
 			}
 		}
 		for _, rc := range module.DataResources {
-			fullName := rc.ProviderConfigKey()
-			inst := moduledeps.ProviderInstance(fullName)
+			addr := rc.ProviderConfigAddr()
+			inst := moduledeps.ProviderInstance(addr.StringCompact())
 			if _, exists := providers[inst]; exists {
 				// Explicit dependency already present
 				continue
 			}
 
 			reason := moduledeps.ProviderDependencyImplicit
-			if _, inherited := inheritProviders[fullName]; inherited {
+			if _, inherited := inheritProviders[addr.String()]; inherited {
 				reason = moduledeps.ProviderDependencyInherited
 			}
 
@@ -161,10 +161,11 @@ func configTreeMergeStateDependencies(root *moduledeps.Module, state *State) {
 
 	findModule := func(path []string) *moduledeps.Module {
 		module := root
-		for _, name := range path[1:] { // skip initial "root"
+		realPath := normalizeModulePath(path)
+		for _, step := range realPath { // skip initial "root"
 			var next *moduledeps.Module
 			for _, cm := range module.Children {
-				if cm.Name == name {
+				if cm.Name == step.Name {
 					next = cm
 					break
 				}
@@ -173,7 +174,7 @@ func configTreeMergeStateDependencies(root *moduledeps.Module, state *State) {
 			if next == nil {
 				// If we didn't find a next node, we'll need to make one
 				next = &moduledeps.Module{
-					Name: name,
+					Name: step.Name,
 				}
 				module.Children = append(module.Children, next)
 			}

terraform/node_data_destroy.go

@@ -1,17 +1,17 @@
 package terraform
 
-// NodeDestroyableDataResource represents a resource that is "plannable":
-// it is ready to be planned in order to create a diff.
+// NodeDestroyableDataResource represents a resource that is "destroyable":
+// it is ready to be destroyed.
 type NodeDestroyableDataResource struct {
-	*NodeAbstractResource
+	*NodeAbstractResourceInstance
 }
 
 // GraphNodeEvalable
 func (n *NodeDestroyableDataResource) EvalTree() EvalNode {
-	addr := n.NodeAbstractResource.Addr
+	addr := n.ResourceInstanceAddr()
 
 	// stateId is the ID to put into the state
-	stateId := addr.stateId()
+	stateId := NewLegacyResourceInstanceAddress(addr).stateId()
 
 	// Just destroy it.
 	var state *InstanceState

terraform/node_data_refresh.go

@@ -2,46 +2,62 @@ package terraform
 
 import (
 	"github.com/hashicorp/terraform/dag"
+	"github.com/hashicorp/terraform/tfdiags"
+	"github.com/zclconf/go-cty/cty"
 )
 
-// NodeRefreshableDataResource represents a resource that is "plannable":
-// it is ready to be planned in order to create a diff.
+// NodeRefreshableDataResource represents a resource that is "refreshable".
 type NodeRefreshableDataResource struct {
-	*NodeAbstractCountResource
+	*NodeAbstractResource
 }
 
+var (
+	_ GraphNodeSubPath              = (*NodeRefreshableDataResource)(nil)
+	_ GraphNodeDynamicExpandable    = (*NodeRefreshableDataResource)(nil)
+	_ GraphNodeReferenceable        = (*NodeRefreshableDataResource)(nil)
+	_ GraphNodeReferencer           = (*NodeRefreshableDataResource)(nil)
+	_ GraphNodeResource             = (*NodeRefreshableDataResource)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodeRefreshableDataResource)(nil)
+)
+
 // GraphNodeDynamicExpandable
 func (n *NodeRefreshableDataResource) DynamicExpand(ctx EvalContext) (*Graph, error) {
+	var diags tfdiags.Diagnostics
+
+	count, countDiags := evaluateResourceCountExpression(n.Config.Count, ctx)
+	diags = diags.Append(countDiags)
+	if countDiags.HasErrors() {
+		return nil, diags.Err()
+	}
+
+	// Next we need to potentially rename an instance address in the state
+	// if we're transitioning whether "count" is set at all.
+	fixResourceCountSetTransition(ctx, n.ResourceAddr().Resource, count != -1)
+
 	// Grab the state which we read
 	state, lock := ctx.State()
 	lock.RLock()
 	defer lock.RUnlock()
 
-	// Expand the resource count which must be available by now from EvalTree
-	count, err := n.Config.Count()
-	if err != nil {
-		return nil, err
-	}
-
 	// The concrete resource factory we'll use
-	concreteResource := func(a *NodeAbstractResource) dag.Vertex {
+	concreteResource := func(a *NodeAbstractResourceInstance) dag.Vertex {
 		// Add the config and state since we don't do that via transforms
 		a.Config = n.Config
 		a.ResolvedProvider = n.ResolvedProvider
 
 		return &NodeRefreshableDataResourceInstance{
-			NodeAbstractResource: a,
+			NodeAbstractResourceInstance: a,
 		}
 	}
 
 	// We also need a destroyable resource for orphans that are a result of a
 	// scaled-in count.
-	concreteResourceDestroyable := func(a *NodeAbstractResource) dag.Vertex {
+	concreteResourceDestroyable := func(a *NodeAbstractResourceInstance) dag.Vertex {
 		// Add the config since we don't do that via transforms
 		a.Config = n.Config
 
 		return &NodeDestroyableDataResource{
-			NodeAbstractResource: a,
+			NodeAbstractResourceInstance: a,
 		}
 	}
 
@@ -67,7 +83,7 @@ func (n *NodeRefreshableDataResource) DynamicExpand(ctx EvalContext) (*Graph, er
 		&AttachStateTransformer{State: state},
 
 		// Targeting
-		&TargetsTransformer{ParsedTargets: n.Targets},
+		&TargetsTransformer{Targets: n.Targets},
 
 		// Connect references so ordering is correct
 		&ReferenceTransformer{},
@@ -83,61 +99,49 @@ func (n *NodeRefreshableDataResource) DynamicExpand(ctx EvalContext) (*Graph, er
 		Name:     "NodeRefreshableDataResource",
 	}
 
-	return b.Build(ctx.Path())
+	graph, diags := b.Build(ctx.Path())
+	return graph, diags.ErrWithWarnings()
 }
 
-// NodeRefreshableDataResourceInstance represents a _single_ resource instance
+// NodeRefreshableDataResourceInstance represents a single resource instance
 // that is refreshable.
 type NodeRefreshableDataResourceInstance struct {
-	*NodeAbstractResource
+	*NodeAbstractResourceInstance
 }
 
 // GraphNodeEvalable
 func (n *NodeRefreshableDataResourceInstance) EvalTree() EvalNode {
-	addr := n.NodeAbstractResource.Addr
+	addr := n.ResourceInstanceAddr()
 
-	// stateId is the ID to put into the state
-	stateId := addr.stateId()
+	// State still uses legacy-style internal ids, so we need to shim to get
+	// a suitable key to use.
+	stateId := NewLegacyResourceInstanceAddress(addr).stateId()
 
-	// Build the instance info. More of this will be populated during eval
-	info := &InstanceInfo{
-		Id:   stateId,
-		Type: addr.Type,
-	}
-
-	// Get the state if we have it, if not we build it
+	// Get the state if we have it. If not, we'll build it.
 	rs := n.ResourceState
 	if rs == nil {
 		rs = &ResourceState{
-			Provider: n.ResolvedProvider,
+			Type:     addr.Resource.Resource.Type,
+			Provider: n.ResolvedProvider.String(),
 		}
 	}
 
-	// If the config isn't empty we update the state
+	// If we have a configuration then we'll build a fresh state.
 	if n.Config != nil {
 		rs = &ResourceState{
-			Type:         n.Config.Type,
-			Provider:     n.Config.Provider,
+			Type:         addr.Resource.Resource.Type,
+			Provider:     n.ResolvedProvider.String(),
 			Dependencies: n.StateReferences(),
 		}
 	}
 
-	// Build the resource for eval
-	resource := &Resource{
-		Name:       addr.Name,
-		Type:       addr.Type,
-		CountIndex: addr.Index,
-	}
-	if resource.CountIndex < 0 {
-		resource.CountIndex = 0
-	}
-
-	// Declare a bunch of variables that are used for state during
-	// evaluation. Most of this are written to by-address below.
-	var config *ResourceConfig
-	var diff *InstanceDiff
+	// These variables are the state for the eval sequence below, and are
+	// updated through pointers.
 	var provider ResourceProvider
+	var providerSchema *ProviderSchema
+	var diff *InstanceDiff
 	var state *InstanceState
+	var configVal cty.Value
 
 	return &EvalSequence{
 		Nodes: []EvalNode{
@@ -153,10 +157,19 @@ func (n *NodeRefreshableDataResourceInstance) EvalTree() EvalNode {
 				State:        &state, // state is nil here
 			},
 
-			&EvalInterpolate{
-				Config:   n.Config.RawConfig.Copy(),
-				Resource: resource,
-				Output:   &config,
+			&EvalGetProvider{
+				Addr:   n.ResolvedProvider,
+				Output: &provider,
+			},
+
+			&EvalReadDataDiff{
+				Addr:           addr.Resource,
+				Config:         n.Config,
+				Provider:       &provider,
+				ProviderSchema: &providerSchema,
+				Output:         &diff,
+				OutputValue:    &configVal,
+				OutputState:    &state,
 			},
 
 			// The rest of this pass can proceed only if there are no
@@ -165,7 +178,7 @@ func (n *NodeRefreshableDataResourceInstance) EvalTree() EvalNode {
 			// apply phases.)
 			&EvalIf{
 				If: func(ctx EvalContext) (bool, error) {
-					if config.ComputedKeys != nil && len(config.ComputedKeys) > 0 {
+					if !configVal.IsWhollyKnown() {
 						return true, EvalEarlyExitError{}
 					}
 
@@ -178,30 +191,11 @@ func (n *NodeRefreshableDataResourceInstance) EvalTree() EvalNode {
 
 					return true, nil
 				},
-
 				Then: EvalNoop{},
 			},
 
-			// The remainder of this pass is the same as running
-			// a "plan" pass immediately followed by an "apply" pass,
-			// populating the state early so it'll be available to
-			// provider configurations that need this data during
-			// refresh/plan.
-			&EvalGetProvider{
-				Name:   n.ResolvedProvider,
-				Output: &provider,
-			},
-
-			&EvalReadDataDiff{
-				Info:        info,
-				Config:      &config,
-				Provider:    &provider,
-				Output:      &diff,
-				OutputState: &state,
-			},
-
 			&EvalReadDataApply{
-				Info:     info,
+				Addr:     addr.Resource,
 				Diff:     &diff,
 				Provider: &provider,
 				Output:   &state,

terraform/node_local.go

@@ -1,10 +1,9 @@
 package terraform
 
 import (
-	"fmt"
-	"strings"
-
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/lang"
 )
 
 // NodeLocal represents a named local value in a particular module.
@@ -12,22 +11,25 @@ import (
 // Local value nodes only have one operation, common to all walk types:
 // evaluate the result and place it in state.
 type NodeLocal struct {
-	PathValue []string
-	Config    *config.Local
+	Addr   addrs.AbsLocalValue
+	Config *configs.Local
 }
 
-func (n *NodeLocal) Name() string {
-	result := fmt.Sprintf("local.%s", n.Config.Name)
-	if len(n.PathValue) > 1 {
-		result = fmt.Sprintf("%s.%s", modulePrefixStr(n.PathValue), result)
-	}
+var (
+	_ GraphNodeSubPath       = (*NodeLocal)(nil)
+	_ RemovableIfNotTargeted = (*NodeLocal)(nil)
+	_ GraphNodeReferenceable = (*NodeLocal)(nil)
+	_ GraphNodeReferencer    = (*NodeLocal)(nil)
+	_ GraphNodeEvalable      = (*NodeLocal)(nil)
+)
 
-	return result
+func (n *NodeLocal) Name() string {
+	return n.Addr.String()
 }
 
 // GraphNodeSubPath
-func (n *NodeLocal) Path() []string {
-	return n.PathValue
+func (n *NodeLocal) Path() addrs.ModuleInstance {
+	return n.Addr.Module
 }
 
 // RemovableIfNotTargeted
@@ -36,31 +38,20 @@ func (n *NodeLocal) RemoveIfNotTargeted() bool {
 }
 
 // GraphNodeReferenceable
-func (n *NodeLocal) ReferenceableName() []string {
-	name := fmt.Sprintf("local.%s", n.Config.Name)
-	return []string{name}
+func (n *NodeLocal) ReferenceableAddrs() []addrs.Referenceable {
+	return []addrs.Referenceable{n.Addr.LocalValue}
 }
 
 // GraphNodeReferencer
-func (n *NodeLocal) References() []string {
-	var result []string
-	result = append(result, ReferencesFromConfig(n.Config.RawConfig)...)
-	for _, v := range result {
-		split := strings.Split(v, "/")
-		for i, s := range split {
-			split[i] = s + ".destroy"
-		}
-
-		result = append(result, strings.Join(split, "/"))
-	}
-
-	return result
+func (n *NodeLocal) References() []*addrs.Reference {
+	refs, _ := lang.ReferencesInExpr(n.Config.Expr)
+	return refs
 }
 
 // GraphNodeEvalable
 func (n *NodeLocal) EvalTree() EvalNode {
 	return &EvalLocal{
-		Name:  n.Config.Name,
-		Value: n.Config.RawConfig,
+		Addr: n.Addr.LocalValue,
+		Expr: n.Config.Expr,
 	}
 }

terraform/node_module_removed.go

@@ -3,22 +3,30 @@ package terraform
 import (
 	"fmt"
 	"log"
-	"reflect"
+
+	"github.com/hashicorp/terraform/addrs"
 )
 
 // NodeModuleRemoved represents a module that is no longer in the
 // config.
 type NodeModuleRemoved struct {
-	PathValue []string
+	Addr addrs.ModuleInstance
 }
 
+var (
+	_ GraphNodeSubPath          = (*NodeModuleRemoved)(nil)
+	_ GraphNodeEvalable         = (*NodeModuleRemoved)(nil)
+	_ GraphNodeReferencer       = (*NodeModuleRemoved)(nil)
+	_ GraphNodeReferenceOutside = (*NodeModuleRemoved)(nil)
+)
+
 func (n *NodeModuleRemoved) Name() string {
-	return fmt.Sprintf("%s (removed)", modulePrefixStr(n.PathValue))
+	return fmt.Sprintf("%s (removed)", n.Addr.String())
 }
 
 // GraphNodeSubPath
-func (n *NodeModuleRemoved) Path() []string {
-	return n.PathValue
+func (n *NodeModuleRemoved) Path() addrs.ModuleInstance {
+	return n.Addr
 }
 
 // GraphNodeEvalable
@@ -26,23 +34,40 @@ func (n *NodeModuleRemoved) EvalTree() EvalNode {
 	return &EvalOpFilter{
 		Ops: []walkOperation{walkRefresh, walkApply, walkDestroy},
 		Node: &EvalDeleteModule{
-			PathValue: n.PathValue,
+			Addr: n.Addr,
 		},
 	}
 }
 
-func (n *NodeModuleRemoved) ReferenceGlobal() bool {
-	return true
+func (n *NodeModuleRemoved) ReferenceOutside() (selfPath, referencePath addrs.ModuleInstance) {
+	// Our "References" implementation indicates that this node depends on
+	// the call to the module it represents, which implicitly depends on
+	// everything inside the module. That reference must therefore be
+	// interpreted in terms of our parent module.
+	return n.Addr, n.Addr.Parent()
 }
 
-func (n *NodeModuleRemoved) References() []string {
-	return []string{modulePrefixStr(n.PathValue)}
+func (n *NodeModuleRemoved) References() []*addrs.Reference {
+	// We depend on the call to the module we represent, because that
+	// implicitly then depends on everything inside that module.
+	// Our ReferenceOutside implementation causes this to be interpreted
+	// within the parent module.
+
+	_, call := n.Addr.CallInstance()
+	return []*addrs.Reference{
+		{
+			Subject: call,
+
+			// No source range here, because there's nothing reasonable for
+			// us to return.
+		},
+	}
 }
 
 // EvalDeleteModule is an EvalNode implementation that removes an empty module
 // entry from the state.
 type EvalDeleteModule struct {
-	PathValue []string
+	Addr addrs.ModuleInstance
 }
 
 func (n *EvalDeleteModule) Eval(ctx EvalContext) (interface{}, error) {
@@ -60,17 +85,33 @@ func (n *EvalDeleteModule) Eval(ctx EvalContext) (interface{}, error) {
 	state.prune()
 
 	// find the module and delete it
+Modules:
 	for i, m := range state.Modules {
-		if reflect.DeepEqual(m.Path, n.PathValue) {
-			if !m.Empty() {
-				// a targeted apply may leave module resources even without a config,
-				// so just log this and return.
-				log.Printf("[DEBUG] cannot remove module %s, not empty", modulePrefixStr(n.PathValue))
-				break
+		// Since state is still using our old-style []string path representation,
+		// comparison is a little awkward. This can be simplified once state
+		// is updated to use addrs.ModuleInstance too.
+		if len(m.Path) != len(n.Addr) {
+			continue Modules
+		}
+		for i, step := range n.Addr {
+			if step.InstanceKey != addrs.NoKey {
+				// Old-style state path can't have keys anyway, so this can
+				// never match.
+				continue Modules
 			}
-			state.Modules = append(state.Modules[:i], state.Modules[i+1:]...)
+			if step.Name != m.Path[i] {
+				continue Modules
+			}
+		}
+
+		if !m.Empty() {
+			// a targeted apply may leave module resources even without a config,
+			// so just log this and return.
+			log.Printf("[DEBUG] not removing %s from state: not empty", n.Addr)
 			break
 		}
+		state.Modules = append(state.Modules[:i], state.Modules[i+1:]...)
+		break
 	}
 
 	return nil, nil

terraform/node_module_variable.go

@@ -1,40 +1,41 @@
 package terraform
 
 import (
-	"fmt"
-
-	"github.com/hashicorp/terraform/config"
-	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/lang"
+	"github.com/zclconf/go-cty/cty"
 )
 
 // NodeApplyableModuleVariable represents a module variable input during
 // the apply step.
 type NodeApplyableModuleVariable struct {
-	PathValue []string
-	Config    *config.Variable  // Config is the var in the config
-	Value     *config.RawConfig // Value is the value that is set
-
-	Module *module.Tree // Antiquated, want to remove
+	Addr   addrs.AbsInputVariableInstance
+	Config *configs.Variable // Config is the var in the config
+	Expr   hcl.Expression    // Expr is the value expression given in the call
 }
 
-func (n *NodeApplyableModuleVariable) Name() string {
-	result := fmt.Sprintf("var.%s", n.Config.Name)
-	if len(n.PathValue) > 1 {
-		result = fmt.Sprintf("%s.%s", modulePrefixStr(n.PathValue), result)
-	}
+// Ensure that we are implementing all of the interfaces we think we are
+// implementing.
+var (
+	_ GraphNodeSubPath          = (*NodeApplyableModuleVariable)(nil)
+	_ RemovableIfNotTargeted    = (*NodeApplyableModuleVariable)(nil)
+	_ GraphNodeReferenceOutside = (*NodeApplyableModuleVariable)(nil)
+	_ GraphNodeReferenceable    = (*NodeApplyableModuleVariable)(nil)
+	_ GraphNodeReferencer       = (*NodeApplyableModuleVariable)(nil)
+	_ GraphNodeEvalable         = (*NodeApplyableModuleVariable)(nil)
+)
 
-	return result
+func (n *NodeApplyableModuleVariable) Name() string {
+	return n.Addr.String()
 }
 
 // GraphNodeSubPath
-func (n *NodeApplyableModuleVariable) Path() []string {
-	// We execute in the parent scope (above our own module) so that
-	// we can access the proper interpolations.
-	if len(n.PathValue) > 2 {
-		return n.PathValue[:len(n.PathValue)-1]
-	}
-
-	return rootModulePath
+func (n *NodeApplyableModuleVariable) Path() addrs.ModuleInstance {
+	// We execute in the parent scope (above our own module) because
+	// expressions in our value are resolved in that context.
+	return n.Addr.Module.Parent()
 }
 
 // RemovableIfNotTargeted
@@ -44,94 +45,95 @@ func (n *NodeApplyableModuleVariable) RemoveIfNotTargeted() bool {
 	return true
 }
 
-// GraphNodeReferenceGlobal
-func (n *NodeApplyableModuleVariable) ReferenceGlobal() bool {
-	// We have to create fully qualified references because we cross
-	// boundaries here: our ReferenceableName is in one path and our
-	// References are from another path.
-	return true
+// GraphNodeReferenceOutside implementation
+func (n *NodeApplyableModuleVariable) ReferenceOutside() (selfPath, referencePath addrs.ModuleInstance) {
+
+	// Module input variables have their value expressions defined in the
+	// context of their calling (parent) module, and so references from
+	// a node of this type should be resolved in the parent module instance.
+	referencePath = n.Addr.Module.Parent()
+
+	// Input variables are _referenced_ from their own module, though.
+	selfPath = n.Addr.Module
+
+	return // uses named return values
 }
 
 // GraphNodeReferenceable
-func (n *NodeApplyableModuleVariable) ReferenceableName() []string {
-	return []string{n.Name()}
+func (n *NodeApplyableModuleVariable) ReferenceableAddrs() []addrs.Referenceable {
+	return []addrs.Referenceable{n.Addr.Variable}
 }
 
 // GraphNodeReferencer
-func (n *NodeApplyableModuleVariable) References() []string {
-	// If we have no value set, we depend on nothing
-	if n.Value == nil {
+func (n *NodeApplyableModuleVariable) References() []*addrs.Reference {
+
+	// If we have no value expression, we cannot depend on anything.
+	if n.Expr == nil {
 		return nil
 	}
 
-	// Can't depend on anything if we're in the root
-	if len(n.PathValue) < 2 {
+	// Variables in the root don't depend on anything, because their values
+	// are gathered prior to the graph walk and recorded in the context.
+	if len(n.Addr.Module) == 0 {
 		return nil
 	}
 
-	// Otherwise, we depend on anything that is in our value, but
-	// specifically in the namespace of the parent path.
-	// Create the prefix based on the path
-	var prefix string
-	if p := n.Path(); len(p) > 0 {
-		prefix = modulePrefixStr(p)
-	}
-
-	result := ReferencesFromConfig(n.Value)
-	return modulePrefixList(result, prefix)
+	// Otherwise, we depend on anything referenced by our value expression.
+	// We ignore diagnostics here under the assumption that we'll re-eval
+	// all these things later and catch them then; for our purposes here,
+	// we only care about valid references.
+	//
+	// Due to our GraphNodeReferenceOutside implementation, the addresses
+	// returned by this function are interpreted in the _parent_ module from
+	// where our associated variable was declared, which is correct because
+	// our value expression is assigned within a "module" block in the parent
+	// module.
+	refs, _ := lang.ReferencesInExpr(n.Expr)
+	return refs
 }
 
 // GraphNodeEvalable
 func (n *NodeApplyableModuleVariable) EvalTree() EvalNode {
 	// If we have no value, do nothing
-	if n.Value == nil {
+	if n.Expr == nil {
 		return &EvalNoop{}
 	}
 
 	// Otherwise, interpolate the value of this variable and set it
 	// within the variables mapping.
-	var config *ResourceConfig
-	variables := make(map[string]interface{})
+	vals := make(map[string]cty.Value)
+
+	_, call := n.Addr.Module.CallInstance()
 
 	return &EvalSequence{
 		Nodes: []EvalNode{
 			&EvalOpFilter{
-				Ops: []walkOperation{walkInput},
-				Node: &EvalInterpolate{
-					Config:        n.Value,
-					Output:        &config,
-					ContinueOnErr: true,
+				Ops: []walkOperation{walkRefresh, walkPlan, walkApply,
+					walkDestroy, walkValidate},
+				Node: &EvalModuleCallArgument{
+					Addr:   n.Addr.Variable,
+					Config: n.Config,
+					Expr:   n.Expr,
+					Values: vals,
+
+					IgnoreDiagnostics: false,
 				},
 			},
 			&EvalOpFilter{
-				Ops: []walkOperation{walkRefresh, walkPlan, walkApply,
-					walkDestroy, walkValidate},
-				Node: &EvalInterpolate{
-					Config: n.Value,
-					Output: &config,
+				Ops: []walkOperation{walkInput},
+				Node: &EvalModuleCallArgument{
+					Addr:   n.Addr.Variable,
+					Config: n.Config,
+					Expr:   n.Expr,
+					Values: vals,
+
+					IgnoreDiagnostics: true,
 				},
 			},
 
-			&EvalVariableBlock{
-				Config:         &config,
-				VariableValues: variables,
-			},
-
-			&EvalCoerceMapVariable{
-				Variables:  variables,
-				ModulePath: n.PathValue,
-				ModuleTree: n.Module,
-			},
-
-			&EvalTypeCheckVariable{
-				Variables:  variables,
-				ModulePath: n.PathValue,
-				ModuleTree: n.Module,
-			},
-
-			&EvalSetVariables{
-				Module:    &n.PathValue[len(n.PathValue)-1],
-				Variables: variables,
+			&EvalSetModuleCallArguments{
+				Module: call,
+				Values: vals,
 			},
 		},
 	}

terraform/node_output.go

@@ -2,31 +2,37 @@ package terraform
 
 import (
 	"fmt"
-	"strings"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/dag"
+	"github.com/hashicorp/terraform/lang"
 )
 
 // NodeApplyableOutput represents an output that is "applyable":
 // it is ready to be applied.
 type NodeApplyableOutput struct {
-	PathValue []string
-	Config    *config.Output // Config is the output in the config
+	Addr   addrs.AbsOutputValue
+	Config *configs.Output // Config is the output in the config
 }
 
-func (n *NodeApplyableOutput) Name() string {
-	result := fmt.Sprintf("output.%s", n.Config.Name)
-	if len(n.PathValue) > 1 {
-		result = fmt.Sprintf("%s.%s", modulePrefixStr(n.PathValue), result)
-	}
+var (
+	_ GraphNodeSubPath          = (*NodeApplyableOutput)(nil)
+	_ RemovableIfNotTargeted    = (*NodeApplyableOutput)(nil)
+	_ GraphNodeTargetDownstream = (*NodeApplyableOutput)(nil)
+	_ GraphNodeReferenceable    = (*NodeApplyableOutput)(nil)
+	_ GraphNodeReferencer       = (*NodeApplyableOutput)(nil)
+	_ GraphNodeReferenceOutside = (*NodeApplyableOutput)(nil)
+	_ GraphNodeEvalable         = (*NodeApplyableOutput)(nil)
+)
 
-	return result
+func (n *NodeApplyableOutput) Name() string {
+	return n.Addr.String()
 }
 
 // GraphNodeSubPath
-func (n *NodeApplyableOutput) Path() []string {
-	return n.PathValue
+func (n *NodeApplyableOutput) Path() addrs.ModuleInstance {
+	return n.Addr.Module
 }
 
 // RemovableIfNotTargeted
@@ -44,27 +50,64 @@ func (n *NodeApplyableOutput) TargetDownstream(targetedDeps, untargetedDeps *dag
 	return true
 }
 
+func referenceOutsideForOutput(addr addrs.AbsOutputValue) (selfPath, referencePath addrs.ModuleInstance) {
+
+	// Output values have their expressions resolved in the context of the
+	// module where they are defined.
+	referencePath = addr.Module
+
+	// ...but they are referenced in the context of their calling module.
+	selfPath = addr.Module.Parent()
+
+	return // uses named return values
+
+}
+
+// GraphNodeReferenceOutside implementation
+func (n *NodeApplyableOutput) ReferenceOutside() (selfPath, referencePath addrs.ModuleInstance) {
+	return referenceOutsideForOutput(n.Addr)
+}
+
+func referenceableAddrsForOutput(addr addrs.AbsOutputValue) []addrs.Referenceable {
+	// An output in the root module can't be referenced at all.
+	if addr.Module.IsRoot() {
+		return nil
+	}
+
+	// Otherwise, we can be referenced via a reference to our output name
+	// on the parent module's call, or via a reference to the entire call.
+	// e.g. module.foo.bar or just module.foo .
+	// Note that our ReferenceOutside method causes these addresses to be
+	// relative to the calling module, not the module where the output
+	// was declared.
+	_, outp := addr.ModuleCallOutput()
+	_, call := addr.Module.CallInstance()
+	return []addrs.Referenceable{outp, call}
+
+}
+
 // GraphNodeReferenceable
-func (n *NodeApplyableOutput) ReferenceableName() []string {
-	name := fmt.Sprintf("output.%s", n.Config.Name)
-	return []string{name}
+func (n *NodeApplyableOutput) ReferenceableAddrs() []addrs.Referenceable {
+	return referenceableAddrsForOutput(n.Addr)
+}
+
+func referencesForOutput(c *configs.Output) []*addrs.Reference {
+	impRefs, _ := lang.ReferencesInExpr(c.Expr)
+	expRefs, _ := lang.References(c.DependsOn)
+	l := len(impRefs) + len(expRefs)
+	if l == 0 {
+		return nil
+	}
+	refs := make([]*addrs.Reference, 0, l)
+	refs = append(refs, impRefs...)
+	refs = append(refs, expRefs...)
+	return refs
+
 }
 
 // GraphNodeReferencer
-func (n *NodeApplyableOutput) References() []string {
-	var result []string
-	result = append(result, n.Config.DependsOn...)
-	result = append(result, ReferencesFromConfig(n.Config.RawConfig)...)
-	for _, v := range result {
-		split := strings.Split(v, "/")
-		for i, s := range split {
-			split[i] = s + ".destroy"
-		}
-
-		result = append(result, strings.Join(split, "/"))
-	}
-
-	return result
+func (n *NodeApplyableOutput) References() []*addrs.Reference {
+	return referencesForOutput(n.Config)
 }
 
 // GraphNodeEvalable
@@ -76,18 +119,18 @@ func (n *NodeApplyableOutput) EvalTree() EvalNode {
 				// before Refresh.
 				Ops: []walkOperation{walkInput},
 				Node: &EvalWriteOutput{
-					Name:          n.Config.Name,
+					Addr:          n.Addr.OutputValue,
 					Sensitive:     n.Config.Sensitive,
-					Value:         n.Config.RawConfig,
+					Expr:          n.Config.Expr,
 					ContinueOnErr: true,
 				},
 			},
 			&EvalOpFilter{
 				Ops: []walkOperation{walkRefresh, walkPlan, walkApply, walkValidate, walkDestroy, walkPlanDestroy},
 				Node: &EvalWriteOutput{
-					Name:      n.Config.Name,
+					Addr:      n.Addr.OutputValue,
 					Sensitive: n.Config.Sensitive,
-					Value:     n.Config.RawConfig,
+					Expr:      n.Config.Expr,
 				},
 			},
 		},
@@ -97,22 +140,25 @@ func (n *NodeApplyableOutput) EvalTree() EvalNode {
 // NodeDestroyableOutput represents an output that is "destroybale":
 // its application will remove the output from the state.
 type NodeDestroyableOutput struct {
-	PathValue []string
-	Config    *config.Output // Config is the output in the config
+	Addr   addrs.AbsOutputValue
+	Config *configs.Output // Config is the output in the config
 }
 
-func (n *NodeDestroyableOutput) Name() string {
-	result := fmt.Sprintf("output.%s (destroy)", n.Config.Name)
-	if len(n.PathValue) > 1 {
-		result = fmt.Sprintf("%s.%s", modulePrefixStr(n.PathValue), result)
-	}
+var (
+	_ GraphNodeSubPath          = (*NodeDestroyableOutput)(nil)
+	_ RemovableIfNotTargeted    = (*NodeDestroyableOutput)(nil)
+	_ GraphNodeTargetDownstream = (*NodeDestroyableOutput)(nil)
+	_ GraphNodeReferencer       = (*NodeDestroyableOutput)(nil)
+	_ GraphNodeEvalable         = (*NodeDestroyableOutput)(nil)
+)
 
-	return result
+func (n *NodeDestroyableOutput) Name() string {
+	return fmt.Sprintf("%s (destroy)", n.Addr.String())
 }
 
 // GraphNodeSubPath
-func (n *NodeDestroyableOutput) Path() []string {
-	return n.PathValue
+func (n *NodeDestroyableOutput) Path() addrs.ModuleInstance {
+	return n.Addr.Module
 }
 
 // RemovableIfNotTargeted
@@ -129,25 +175,13 @@ func (n *NodeDestroyableOutput) TargetDownstream(targetedDeps, untargetedDeps *d
 }
 
 // GraphNodeReferencer
-func (n *NodeDestroyableOutput) References() []string {
-	var result []string
-	result = append(result, n.Config.DependsOn...)
-	result = append(result, ReferencesFromConfig(n.Config.RawConfig)...)
-	for _, v := range result {
-		split := strings.Split(v, "/")
-		for i, s := range split {
-			split[i] = s + ".destroy"
-		}
-
-		result = append(result, strings.Join(split, "/"))
-	}
-
-	return result
+func (n *NodeDestroyableOutput) References() []*addrs.Reference {
+	return referencesForOutput(n.Config)
 }
 
 // GraphNodeEvalable
 func (n *NodeDestroyableOutput) EvalTree() EvalNode {
 	return &EvalDeleteOutput{
-		Name: n.Config.Name,
+		Addr: n.Addr.OutputValue,
 	}
 }

terraform/node_output_orphan.go

@@ -2,31 +2,39 @@ package terraform
 
 import (
 	"fmt"
+
+	"github.com/hashicorp/terraform/addrs"
 )
 
 // NodeOutputOrphan represents an output that is an orphan.
 type NodeOutputOrphan struct {
-	OutputName string
-	PathValue  []string
+	Addr addrs.AbsOutputValue
 }
 
-func (n *NodeOutputOrphan) Name() string {
-	result := fmt.Sprintf("output.%s (orphan)", n.OutputName)
-	if len(n.PathValue) > 1 {
-		result = fmt.Sprintf("%s.%s", modulePrefixStr(n.PathValue), result)
-	}
+var (
+	_ GraphNodeSubPath          = (*NodeOutputOrphan)(nil)
+	_ GraphNodeReferenceable    = (*NodeOutputOrphan)(nil)
+	_ GraphNodeReferenceOutside = (*NodeOutputOrphan)(nil)
+	_ GraphNodeEvalable         = (*NodeOutputOrphan)(nil)
+)
 
-	return result
+func (n *NodeOutputOrphan) Name() string {
+	return fmt.Sprintf("%s (orphan)", n.Addr.String())
+}
+
+// GraphNodeReferenceOutside implementation
+func (n *NodeOutputOrphan) ReferenceOutside() (selfPath, referencePath addrs.ModuleInstance) {
+	return referenceOutsideForOutput(n.Addr)
 }
 
 // GraphNodeReferenceable
-func (n *NodeOutputOrphan) ReferenceableName() []string {
-	return []string{"output." + n.OutputName}
+func (n *NodeOutputOrphan) ReferenceableAddrs() []addrs.Referenceable {
+	return referenceableAddrsForOutput(n.Addr)
 }
 
 // GraphNodeSubPath
-func (n *NodeOutputOrphan) Path() []string {
-	return n.PathValue
+func (n *NodeOutputOrphan) Path() addrs.ModuleInstance {
+	return n.Addr.Module
 }
 
 // GraphNodeEvalable
@@ -34,7 +42,7 @@ func (n *NodeOutputOrphan) EvalTree() EvalNode {
 	return &EvalOpFilter{
 		Ops: []walkOperation{walkRefresh, walkApply, walkDestroy},
 		Node: &EvalDeleteOutput{
-			Name: n.OutputName,
+			Addr: n.Addr.OutputValue,
 		},
 	}
 }

terraform/node_provider_abstract.go

@@ -1,10 +1,9 @@
 package terraform
 
 import (
-	"fmt"
-	"strings"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
 
-	"github.com/hashicorp/terraform/config"
 	"github.com/hashicorp/terraform/dag"
 )
 
@@ -15,37 +14,32 @@ type ConcreteProviderNodeFunc func(*NodeAbstractProvider) dag.Vertex
 // NodeAbstractProvider represents a provider that has no associated operations.
 // It registers all the common interfaces across operations for providers.
 type NodeAbstractProvider struct {
-	NameValue string
-	PathValue []string
+	Addr addrs.AbsProviderConfig
 
 	// The fields below will be automatically set using the Attach
 	// interfaces if you're running those transforms, but also be explicitly
 	// set if you already have that information.
 
-	Config *config.ProviderConfig
+	Config *configs.Provider
+	Schema *ProviderSchema
 }
 
-func ResolveProviderName(name string, path []string) string {
-	if strings.Contains(name, "provider.") {
-		// already resolved
-		return name
-	}
-
-	name = fmt.Sprintf("provider.%s", name)
-	if len(path) >= 1 {
-		name = fmt.Sprintf("%s.%s", modulePrefixStr(path), name)
-	}
-
-	return name
-}
+var (
+	_ GraphNodeSubPath        = (*NodeAbstractProvider)(nil)
+	_ RemovableIfNotTargeted  = (*NodeAbstractProvider)(nil)
+	_ GraphNodeReferencer     = (*NodeAbstractProvider)(nil)
+	_ GraphNodeProvider       = (*NodeAbstractProvider)(nil)
+	_ GraphNodeAttachProvider = (*NodeAbstractProvider)(nil)
+	_ dag.GraphNodeDotter     = (*NodeAbstractProvider)(nil)
+)
 
 func (n *NodeAbstractProvider) Name() string {
-	return ResolveProviderName(n.NameValue, n.PathValue)
+	return n.Addr.String()
 }
 
 // GraphNodeSubPath
-func (n *NodeAbstractProvider) Path() []string {
-	return n.PathValue
+func (n *NodeAbstractProvider) Path() addrs.ModuleInstance {
+	return n.Addr.Module
 }
 
 // RemovableIfNotTargeted
@@ -56,21 +50,21 @@ func (n *NodeAbstractProvider) RemoveIfNotTargeted() bool {
 }
 
 // GraphNodeReferencer
-func (n *NodeAbstractProvider) References() []string {
-	if n.Config == nil {
+func (n *NodeAbstractProvider) References() []*addrs.Reference {
+	if n.Config == nil || n.Schema == nil {
 		return nil
 	}
 
-	return ReferencesFromConfig(n.Config.RawConfig)
+	return ReferencesFromConfig(n.Config.Config, n.Schema.Provider)
 }
 
 // GraphNodeProvider
-func (n *NodeAbstractProvider) ProviderName() string {
-	return n.NameValue
+func (n *NodeAbstractProvider) ProviderAddr() addrs.AbsProviderConfig {
+	return n.Addr
 }
 
 // GraphNodeProvider
-func (n *NodeAbstractProvider) ProviderConfig() *config.ProviderConfig {
+func (n *NodeAbstractProvider) ProviderConfig() *configs.Provider {
 	if n.Config == nil {
 		return nil
 	}
@@ -79,10 +73,15 @@ func (n *NodeAbstractProvider) ProviderConfig() *config.ProviderConfig {
 }
 
 // GraphNodeAttachProvider
-func (n *NodeAbstractProvider) AttachProvider(c *config.ProviderConfig) {
+func (n *NodeAbstractProvider) AttachProvider(c *configs.Provider) {
 	n.Config = c
 }
 
+// GraphNodeAttachProvider
+func (n *NodeAbstractProvider) AttachProviderSchema(s *ProviderSchema) {
+	n.Schema = s
+}
+
 // GraphNodeDotter impl.
 func (n *NodeAbstractProvider) DotNode(name string, opts *dag.DotOpts) *dag.DotNode {
 	return &dag.DotNode{

terraform/node_provider_disabled.go

@@ -2,6 +2,8 @@ package terraform
 
 import (
 	"fmt"
+
+	"github.com/hashicorp/terraform/dag"
 )
 
 // NodeDisabledProvider represents a provider that is disabled. A disabled
@@ -11,24 +13,15 @@ type NodeDisabledProvider struct {
 	*NodeAbstractProvider
 }
 
+var (
+	_ GraphNodeSubPath        = (*NodeDisabledProvider)(nil)
+	_ RemovableIfNotTargeted  = (*NodeDisabledProvider)(nil)
+	_ GraphNodeReferencer     = (*NodeDisabledProvider)(nil)
+	_ GraphNodeProvider       = (*NodeDisabledProvider)(nil)
+	_ GraphNodeAttachProvider = (*NodeDisabledProvider)(nil)
+	_ dag.GraphNodeDotter     = (*NodeDisabledProvider)(nil)
+)
+
 func (n *NodeDisabledProvider) Name() string {
 	return fmt.Sprintf("%s (disabled)", n.NodeAbstractProvider.Name())
 }
-
-// GraphNodeEvalable
-func (n *NodeDisabledProvider) EvalTree() EvalNode {
-	var resourceConfig *ResourceConfig
-	return &EvalSequence{
-		Nodes: []EvalNode{
-			&EvalInterpolateProvider{
-				Config: n.ProviderConfig(),
-				Output: &resourceConfig,
-			},
-			&EvalBuildProviderConfig{
-				Provider: n.ProviderName(),
-				Config:   &resourceConfig,
-				Output:   &resourceConfig,
-			},
-		},
-	}
-}

terraform/node_provisioner.go

@@ -3,6 +3,7 @@ package terraform
 import (
 	"fmt"
 
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/config"
 )
 
@@ -10,7 +11,7 @@ import (
 // It registers all the common interfaces across operations for providers.
 type NodeProvisioner struct {
 	NameValue string
-	PathValue []string
+	PathValue addrs.ModuleInstance
 
 	// The fields below will be automatically set using the Attach
 	// interfaces if you're running those transforms, but also be explicitly
@@ -19,17 +20,23 @@ type NodeProvisioner struct {
 	Config *config.ProviderConfig
 }
 
+var (
+	_ GraphNodeSubPath     = (*NodeProvisioner)(nil)
+	_ GraphNodeProvisioner = (*NodeProvisioner)(nil)
+	_ GraphNodeEvalable    = (*NodeProvisioner)(nil)
+)
+
 func (n *NodeProvisioner) Name() string {
 	result := fmt.Sprintf("provisioner.%s", n.NameValue)
 	if len(n.PathValue) > 1 {
-		result = fmt.Sprintf("%s.%s", modulePrefixStr(n.PathValue), result)
+		result = fmt.Sprintf("%s.%s", n.PathValue.String(), result)
 	}
 
 	return result
 }
 
 // GraphNodeSubPath
-func (n *NodeProvisioner) Path() []string {
+func (n *NodeProvisioner) Path() addrs.ModuleInstance {
 	return n.PathValue
 }
 

terraform/node_resource_abstract.go

@@ -2,9 +2,17 @@ package terraform
 
 import (
 	"fmt"
-	"strings"
+	"log"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/hcl2/hcl/hclsyntax"
+
+	"github.com/hashicorp/terraform/config/configschema"
+	"github.com/hashicorp/terraform/lang"
+
+	"github.com/hashicorp/terraform/addrs"
+
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/dag"
 )
 
@@ -16,222 +24,366 @@ type ConcreteResourceNodeFunc func(*NodeAbstractResource) dag.Vertex
 // The type of operation cannot be assumed, only that this node represents
 // the given resource.
 type GraphNodeResource interface {
-	ResourceAddr() *ResourceAddress
+	ResourceAddr() addrs.AbsResource
+}
+
+// ConcreteResourceInstanceNodeFunc is a callback type used to convert an
+// abstract resource instance to a concrete one of some type.
+type ConcreteResourceInstanceNodeFunc func(*NodeAbstractResourceInstance) dag.Vertex
+
+// GraphNodeResourceInstance is implemented by any nodes that represent
+// a resource instance. A single resource may have multiple instances if,
+// for example, the "count" or "for_each" argument is used for it in
+// configuration.
+type GraphNodeResourceInstance interface {
+	ResourceInstanceAddr() addrs.AbsResourceInstance
 }
 
 // NodeAbstractResource represents a resource that has no associated
 // operations. It registers all the interfaces for a resource that common
 // across multiple operation types.
 type NodeAbstractResource struct {
-	Addr *ResourceAddress // Addr is the address for this resource
+	Addr addrs.AbsResource // Addr is the address for this resource
 
 	// The fields below will be automatically set using the Attach
 	// interfaces if you're running those transforms, but also be explicitly
 	// set if you already have that information.
 
-	Config        *config.Resource // Config is the resource in the config
-	ResourceState *ResourceState   // ResourceState is the ResourceState for this
+	Schema *configschema.Block // Schema for processing the configuration body
+	Config *configs.Resource   // Config is the resource in the config
 
-	Targets []ResourceAddress // Set from GraphNodeTargetable
+	ProvisionerSchemas map[string]*configschema.Block
+
+	Targets []addrs.Targetable // Set from GraphNodeTargetable
 
 	// The address of the provider this resource will use
-	ResolvedProvider string
+	ResolvedProvider addrs.AbsProviderConfig
+}
+
+var (
+	_ GraphNodeSubPath              = (*NodeAbstractResource)(nil)
+	_ GraphNodeReferenceable        = (*NodeAbstractResource)(nil)
+	_ GraphNodeReferencer           = (*NodeAbstractResource)(nil)
+	_ GraphNodeProviderConsumer     = (*NodeAbstractResource)(nil)
+	_ GraphNodeProvisionerConsumer  = (*NodeAbstractResource)(nil)
+	_ GraphNodeResource             = (*NodeAbstractResource)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodeAbstractResource)(nil)
+	_ GraphNodeTargetable           = (*NodeAbstractResource)(nil)
+	_ dag.GraphNodeDotter           = (*NodeAbstractResource)(nil)
+)
+
+// NewNodeAbstractResource creates an abstract resource graph node for
+// the given absolute resource address.
+func NewNodeAbstractResource(addr addrs.AbsResource) *NodeAbstractResource {
+	return &NodeAbstractResource{
+		Addr: addr,
+	}
+}
+
+// NodeAbstractResourceInstance represents a resource instance with no
+// associated operations. It embeds NodeAbstractResource but additionally
+// contains an instance key, used to identify one of potentially many
+// instances that were created from a resource in configuration, e.g. using
+// the "count" or "for_each" arguments.
+type NodeAbstractResourceInstance struct {
+	NodeAbstractResource
+	InstanceKey addrs.InstanceKey
+
+	// The fields below will be automatically set using the Attach
+	// interfaces if you're running those transforms, but also be explicitly
+	// set if you already have that information.
+
+	ResourceState *ResourceState // the ResourceState for this instance
+}
+
+var (
+	_ GraphNodeSubPath              = (*NodeAbstractResourceInstance)(nil)
+	_ GraphNodeReferenceable        = (*NodeAbstractResourceInstance)(nil)
+	_ GraphNodeReferencer           = (*NodeAbstractResourceInstance)(nil)
+	_ GraphNodeProviderConsumer     = (*NodeAbstractResourceInstance)(nil)
+	_ GraphNodeProvisionerConsumer  = (*NodeAbstractResourceInstance)(nil)
+	_ GraphNodeResource             = (*NodeAbstractResourceInstance)(nil)
+	_ GraphNodeResourceInstance     = (*NodeAbstractResourceInstance)(nil)
+	_ GraphNodeAttachResourceState  = (*NodeAbstractResourceInstance)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodeAbstractResourceInstance)(nil)
+	_ GraphNodeTargetable           = (*NodeAbstractResource)(nil)
+	_ dag.GraphNodeDotter           = (*NodeAbstractResourceInstance)(nil)
+)
+
+// NewNodeAbstractResourceInstance creates an abstract resource instance graph
+// node for the given absolute resource instance address.
+func NewNodeAbstractResourceInstance(addr addrs.AbsResourceInstance) *NodeAbstractResourceInstance {
+	// Due to the fact that we embed NodeAbstractResource, the given address
+	// actually ends up split between the resource address in the embedded
+	// object and the InstanceKey field in our own struct. The
+	// ResourceInstanceAddr method will stick these back together again on
+	// request.
+	return &NodeAbstractResourceInstance{
+		NodeAbstractResource: NodeAbstractResource{
+			Addr: addr.ContainingResource(),
+		},
+		InstanceKey: addr.Resource.Key,
+	}
 }
 
 func (n *NodeAbstractResource) Name() string {
-	return n.Addr.String()
+	return n.ResourceAddr().String()
+}
+
+func (n *NodeAbstractResourceInstance) Name() string {
+	return n.ResourceInstanceAddr().String()
 }
 
 // GraphNodeSubPath
-func (n *NodeAbstractResource) Path() []string {
-	return n.Addr.Path
+func (n *NodeAbstractResource) Path() addrs.ModuleInstance {
+	return n.Addr.Module
 }
 
 // GraphNodeReferenceable
-func (n *NodeAbstractResource) ReferenceableName() []string {
-	// We always are referenceable as "type.name" as long as
-	// we have a config or address. Determine what that value is.
-	var id string
-	if n.Config != nil {
-		id = n.Config.Id()
-	} else if n.Addr != nil {
-		addrCopy := n.Addr.Copy()
-		addrCopy.Path = nil // ReferenceTransformer handles paths
-		addrCopy.Index = -1 // We handle indexes below
-		id = addrCopy.String()
-	} else {
-		// No way to determine our type.name, just return
-		return nil
+func (n *NodeAbstractResource) ReferenceableAddrs() []addrs.Referenceable {
+	return []addrs.Referenceable{n.Addr.Resource}
+}
+
+// GraphNodeReferenceable
+func (n *NodeAbstractResourceInstance) ReferenceableAddrs() []addrs.Referenceable {
+	addr := n.ResourceInstanceAddr()
+	return []addrs.Referenceable{
+		addr.Resource,
+
+		// A resource instance can also be referenced by the address of its
+		// containing resource, so that e.g. a reference to aws_instance.foo
+		// would match both aws_instance.foo[0] and aws_instance.foo[1].
+		addr.ContainingResource().Resource,
 	}
-
-	var result []string
-
-	// Always include our own ID. This is primarily for backwards
-	// compatibility with states that didn't yet support the more
-	// specific dep string.
-	result = append(result, id)
-
-	// We represent all multi-access
-	result = append(result, fmt.Sprintf("%s.*", id))
-
-	// We represent either a specific number, or all numbers
-	suffix := "N"
-	if n.Addr != nil {
-		idx := n.Addr.Index
-		if idx == -1 {
-			idx = 0
-		}
-
-		suffix = fmt.Sprintf("%d", idx)
-	}
-	result = append(result, fmt.Sprintf("%s.%s", id, suffix))
-
-	return result
 }
 
 // GraphNodeReferencer
-func (n *NodeAbstractResource) References() []string {
-	// If we have a config, that is our source of truth
+func (n *NodeAbstractResource) References() []*addrs.Reference {
+	// If we have a config then we prefer to use that.
 	if c := n.Config; c != nil {
-		// Grab all the references
-		var result []string
-		result = append(result, c.DependsOn...)
-		result = append(result, ReferencesFromConfig(c.RawCount)...)
-		result = append(result, ReferencesFromConfig(c.RawConfig)...)
-		for _, p := range c.Provisioners {
-			if p.When == config.ProvisionerWhenCreate {
-				result = append(result, ReferencesFromConfig(p.ConnInfo)...)
-				result = append(result, ReferencesFromConfig(p.RawConfig)...)
+		var result []*addrs.Reference
+
+		for _, traversal := range c.DependsOn {
+			ref, err := addrs.ParseRef(traversal)
+			if err != nil {
+				// We ignore this here, because this isn't a suitable place to return
+				// errors. This situation should be caught and rejected during
+				// validation.
+				log.Printf("[ERROR] Can't parse %#v from depends_on as reference: %s", traversal, err)
+				continue
 			}
+
+			result = append(result, ref)
 		}
 
-		return uniqueStrings(result)
+		refs, _ := lang.ReferencesInExpr(c.Count)
+		result = append(result, refs...)
+		refs, _ = lang.ReferencesInBlock(c.Config, n.Schema)
+		result = append(result, refs...)
+		if c.Managed != nil {
+			for _, p := range c.Managed.Provisioners {
+				if p.When != configs.ProvisionerWhenCreate {
+					continue
+				}
+				refs, _ = lang.ReferencesInBlock(p.Connection.Config, connectionBlockSupersetSchema)
+				result = append(result, refs...)
+
+				schema := n.ProvisionerSchemas[p.Type]
+				refs, _ = lang.ReferencesInBlock(p.Config, schema)
+				result = append(result, refs...)
+			}
+		}
+		return result
 	}
 
-	// If we have state, that is our next source
+	// Otherwise, we have no references.
+	return nil
+}
+
+// GraphNodeReferencer
+func (n *NodeAbstractResourceInstance) References() []*addrs.Reference {
+	// If we have a configuration attached then we'll delegate to our
+	// embedded abstract resource, which knows how to extract dependencies
+	// from configuration.
+	if n.Config != nil {
+		return n.NodeAbstractResource.References()
+	}
+
+	// Otherwise, if we have state then we'll use the values stored in state
+	// as a fallback.
 	if s := n.ResourceState; s != nil {
-		return s.Dependencies
+		// State is still storing dependencies as old-style strings, so we'll
+		// need to do a little work here to massage this to the form we now
+		// want.
+		var result []*addrs.Reference
+		for _, legacyDep := range s.Dependencies {
+			traversal, diags := hclsyntax.ParseTraversalAbs([]byte(legacyDep), "", hcl.Pos{})
+			if diags.HasErrors() {
+				log.Printf("[ERROR] Can't parse %q from dependencies in state as a reference: invalid syntax", legacyDep)
+				continue
+			}
+			ref, err := addrs.ParseRef(traversal)
+			if err != nil {
+				log.Printf("[ERROR] Can't parse %q from dependencies in state as a reference: invalid syntax", legacyDep)
+				continue
+			}
+
+			result = append(result, ref)
+		}
+		return result
 	}
 
+	// If we have neither config nor state then we have no references.
 	return nil
 }
 
 // StateReferences returns the dependencies to put into the state for
 // this resource.
 func (n *NodeAbstractResource) StateReferences() []string {
-	self := n.ReferenceableName()
-
-	// Determine what our "prefix" is for checking for references to
-	// ourself.
-	addrCopy := n.Addr.Copy()
-	addrCopy.Index = -1
-	selfPrefix := addrCopy.String() + "."
+	selfAddrs := n.ReferenceableAddrs()
 
 	depsRaw := n.References()
 	deps := make([]string, 0, len(depsRaw))
 	for _, d := range depsRaw {
-		// Ignore any variable dependencies
-		if strings.HasPrefix(d, "var.") {
-			continue
-		}
-
-		// If this has a backup ref, ignore those for now. The old state
-		// file never contained those and I'd rather store the rich types we
-		// add in the future.
-		if idx := strings.IndexRune(d, '/'); idx != -1 {
-			d = d[:idx]
-		}
-
-		// If we're referencing ourself, then ignore it
-		found := false
-		for _, s := range self {
-			if d == s {
-				found = true
+		switch tr := d.Subject.(type) {
+		case addrs.ResourceInstance:
+			// For historical reasons, state uses dot-separated instance keys,
+			// rather than bracketed as in our modern syntax.
+			var suffix string
+			switch tk := tr.Key.(type) {
+			case addrs.IntKey:
+				suffix = fmt.Sprintf(".%d", int(tk))
+			case addrs.StringKey:
+				suffix = fmt.Sprintf(".%s", string(tk))
 			}
+			key := tr.Resource.String() + suffix
+			deps = append(deps, key)
+		case addrs.Resource:
+			depStr := tr.String()
+			selfRef := false
+			for _, selfAddr := range selfAddrs {
+				if selfAddr.String() == depStr {
+					selfRef = true
+					break
+				}
+			}
+			if !selfRef { // Don't create self-references
+				deps = append(deps, tr.String())
+			}
+		case addrs.ModuleCallInstance:
+			deps = append(deps, tr.String())
+		case addrs.ModuleCallOutput:
+			// For state dependencies, we simplify outputs to just refer
+			// to the module as a whole. It's not really clear why we do this,
+			// but this logic is preserved from before the 0.12 rewrite of
+			// this function.
+			deps = append(deps, tr.Call.String())
+		default:
+			// No other reference types are recorded in the state.
 		}
-		if found {
-			continue
-		}
-
-		// If this is a reference to ourself and a specific index, we keep
-		// it. For example, if this resource is "foo.bar" and the reference
-		// is "foo.bar.0" then we keep it exact. Otherwise, we strip it.
-		if strings.HasSuffix(d, ".0") && !strings.HasPrefix(d, selfPrefix) {
-			d = d[:len(d)-2]
-		}
-
-		// This is sad. The dependencies are currently in the format of
-		// "module.foo.bar" (the full field). This strips the field off.
-		if strings.HasPrefix(d, "module.") {
-			parts := strings.SplitN(d, ".", 3)
-			d = strings.Join(parts[0:2], ".")
-		}
-
-		deps = append(deps, d)
 	}
 
 	return deps
 }
 
-func (n *NodeAbstractResource) SetProvider(p string) {
+func (n *NodeAbstractResource) SetProvider(p addrs.AbsProviderConfig) {
 	n.ResolvedProvider = p
 }
 
 // GraphNodeProviderConsumer
-func (n *NodeAbstractResource) ProvidedBy() string {
+func (n *NodeAbstractResource) ProvidedBy() (addrs.AbsProviderConfig, bool) {
 	// If we have a config we prefer that above all else
 	if n.Config != nil {
-		return resourceProvider(n.Config.Type, n.Config.Provider)
+		relAddr := n.Config.ProviderConfigAddr()
+		return relAddr.Absolute(n.Path()), false
+	}
+
+	// Use our type and containing module path to guess a provider configuration address
+	return addrs.NewDefaultProviderConfig(n.Addr.Resource.Type).Absolute(n.Addr.Module), false
+}
+
+// GraphNodeProviderConsumer
+func (n *NodeAbstractResourceInstance) ProvidedBy() (addrs.AbsProviderConfig, bool) {
+	// If we have a config we prefer that above all else
+	if n.Config != nil {
+		relAddr := n.Config.ProviderConfigAddr()
+		return relAddr.Absolute(n.Path()), false
 	}
 
 	// If we have state, then we will use the provider from there
 	if n.ResourceState != nil && n.ResourceState.Provider != "" {
-		return n.ResourceState.Provider
+		traversal, parseDiags := hclsyntax.ParseTraversalAbs([]byte(n.ResourceState.Provider), "", hcl.Pos{})
+		if parseDiags.HasErrors() {
+			log.Printf("[ERROR] %s has syntax-invalid provider address %q", n.Addr, n.ResourceState.Provider)
+			goto Guess
+		}
+
+		addr, diags := addrs.ParseAbsProviderConfig(traversal)
+		if diags.HasErrors() {
+			log.Printf("[ERROR] %s has content-invalid provider address %q", n.Addr, n.ResourceState.Provider)
+			goto Guess
+		}
+
+		// An address from the state must match exactly, since we must ensure
+		// we refresh/destroy a resource with the same provider configuration
+		// that created it.
+		return addr, true
 	}
 
-	// Use our type
-	return resourceProvider(n.Addr.Type, "")
+Guess:
+	// Use our type and containing module path to guess a provider configuration address
+	return addrs.NewDefaultProviderConfig(n.Addr.Resource.Type).Absolute(n.Addr.Module), false
 }
 
 // GraphNodeProvisionerConsumer
 func (n *NodeAbstractResource) ProvisionedBy() []string {
 	// If we have no configuration, then we have no provisioners
-	if n.Config == nil {
+	if n.Config == nil || n.Config.Managed == nil {
 		return nil
 	}
 
 	// Build the list of provisioners we need based on the configuration.
 	// It is okay to have duplicates here.
-	result := make([]string, len(n.Config.Provisioners))
-	for i, p := range n.Config.Provisioners {
+	result := make([]string, len(n.Config.Managed.Provisioners))
+	for i, p := range n.Config.Managed.Provisioners {
 		result[i] = p.Type
 	}
 
 	return result
 }
 
-// GraphNodeResource, GraphNodeAttachResourceState
-func (n *NodeAbstractResource) ResourceAddr() *ResourceAddress {
+// GraphNodeProvisionerConsumer
+func (n *NodeAbstractResource) SetProvisionerSchema(name string, schema *configschema.Block) {
+	n.ProvisionerSchemas[name] = schema
+}
+
+// GraphNodeResource
+func (n *NodeAbstractResource) ResourceAddr() addrs.AbsResource {
 	return n.Addr
 }
 
+// GraphNodeResourceInstance
+func (n *NodeAbstractResourceInstance) ResourceInstanceAddr() addrs.AbsResourceInstance {
+	return n.NodeAbstractResource.Addr.Instance(n.InstanceKey)
+}
+
 // GraphNodeAddressable, TODO: remove, used by target, should unify
 func (n *NodeAbstractResource) ResourceAddress() *ResourceAddress {
-	return n.ResourceAddr()
+	return NewLegacyResourceAddress(n.Addr)
 }
 
 // GraphNodeTargetable
-func (n *NodeAbstractResource) SetTargets(targets []ResourceAddress) {
+func (n *NodeAbstractResource) SetTargets(targets []addrs.Targetable) {
 	n.Targets = targets
 }
 
 // GraphNodeAttachResourceState
-func (n *NodeAbstractResource) AttachResourceState(s *ResourceState) {
+func (n *NodeAbstractResourceInstance) AttachResourceState(s *ResourceState) {
 	n.ResourceState = s
 }
 
 // GraphNodeAttachResourceConfig
-func (n *NodeAbstractResource) AttachResourceConfig(c *config.Resource) {
+func (n *NodeAbstractResource) AttachResourceConfig(c *configs.Resource) {
 	n.Config = c
 }
 

terraform/node_resource_abstract_count.go

@@ -1,50 +0,0 @@
-package terraform
-
-// NodeAbstractCountResource should be embedded instead of NodeAbstractResource
-// if the resource has a `count` value that needs to be expanded.
-//
-// The embedder should implement `DynamicExpand` to process the count.
-type NodeAbstractCountResource struct {
-	*NodeAbstractResource
-
-	// Validate, if true, will perform the validation for the count.
-	// This should only be turned on for the "validate" operation.
-	Validate bool
-}
-
-// GraphNodeEvalable
-func (n *NodeAbstractCountResource) EvalTree() EvalNode {
-	// We only check if the count is computed if we're not validating.
-	// If we're validating we allow computed counts since they just turn
-	// into more computed values.
-	var evalCountCheckComputed EvalNode
-	if !n.Validate {
-		evalCountCheckComputed = &EvalCountCheckComputed{Resource: n.Config}
-	}
-
-	return &EvalSequence{
-		Nodes: []EvalNode{
-			// The EvalTree for a plannable resource primarily involves
-			// interpolating the count since it can contain variables
-			// we only just received access to.
-			//
-			// With the interpolated count, we can then DynamicExpand
-			// into the proper number of instances.
-			&EvalInterpolate{Config: n.Config.RawCount},
-
-			// Check if the count is computed
-			evalCountCheckComputed,
-
-			// If validation is enabled, perform the validation
-			&EvalIf{
-				If: func(ctx EvalContext) (bool, error) {
-					return n.Validate, nil
-				},
-
-				Then: &EvalValidateCount{Resource: n.Config},
-			},
-
-			&EvalCountFixZeroOneBoundary{Resource: n.Config},
-		},
-	}
-}

terraform/node_resource_apply.go

@@ -3,112 +3,108 @@ package terraform
 import (
 	"fmt"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/zclconf/go-cty/cty"
 )
 
-// NodeApplyableResource represents a resource that is "applyable":
+// NodeApplyableResourceInstance represents a resource that is "applyable":
 // it is ready to be applied and is represented by a diff.
-type NodeApplyableResource struct {
-	*NodeAbstractResource
+type NodeApplyableResourceInstance struct {
+	*NodeAbstractResourceInstance
 }
 
+var (
+	_ GraphNodeResource         = (*NodeApplyableResourceInstance)(nil)
+	_ GraphNodeResourceInstance = (*NodeApplyableResourceInstance)(nil)
+	_ GraphNodeCreator          = (*NodeApplyableResourceInstance)(nil)
+	_ GraphNodeReferencer       = (*NodeApplyableResourceInstance)(nil)
+	_ GraphNodeEvalable         = (*NodeApplyableResourceInstance)(nil)
+)
+
 // GraphNodeCreator
-func (n *NodeApplyableResource) CreateAddr() *ResourceAddress {
-	return n.NodeAbstractResource.Addr
+func (n *NodeApplyableResourceInstance) CreateAddr() *addrs.AbsResourceInstance {
+	addr := n.ResourceInstanceAddr()
+	return &addr
 }
 
-// GraphNodeReferencer, overriding NodeAbstractResource
-func (n *NodeApplyableResource) References() []string {
-	result := n.NodeAbstractResource.References()
+// GraphNodeReferencer, overriding NodeAbstractResourceInstance
+func (n *NodeApplyableResourceInstance) References() []*addrs.Reference {
+	// Start with the usual resource instance implementation
+	ret := n.NodeAbstractResourceInstance.References()
 
-	// The "apply" side of a resource generally also depends on the
-	// destruction of its dependencies as well. For example, if a LB
-	// references a set of VMs with ${vm.foo.*.id}, then we must wait for
-	// the destruction so we get the newly updated list of VMs.
+	// Applying a resource must also depend on the destruction of any of its
+	// dependencies, since this may for example affect the outcome of
+	// evaluating an entire list of resources with "count" set (by reducing
+	// the count).
 	//
-	// The exception here is CBD. When CBD is set, we don't do this since
-	// it would create a cycle. By not creating a cycle, we require two
-	// applies since the first apply the creation step will use the OLD
-	// values (pre-destroy) and the second step will update.
-	//
-	// This is how Terraform behaved with "legacy" graphs (TF <= 0.7.x).
-	// We mimic that behavior here now and can improve upon it in the future.
-	//
-	// This behavior is tested in graph_build_apply_test.go to test ordering.
-	cbd := n.Config != nil && n.Config.Lifecycle.CreateBeforeDestroy
+	// However, we can't do this in create_before_destroy mode because that
+	// would create a dependency cycle. We make a compromise here of requiring
+	// changes to be updated across two applies in this case, since the first
+	// plan will use the old values.
+	cbd := n.Config != nil && n.Config.Managed != nil && n.Config.Managed.CreateBeforeDestroy
 	if !cbd {
-		// The "apply" side of a resource always depends on the destruction
-		// of all its dependencies in addition to the creation.
-		for _, v := range result {
-			result = append(result, v+".destroy")
+		for _, ref := range ret {
+			switch tr := ref.Subject.(type) {
+			case addrs.ResourceInstance:
+				newRef := *ref // shallow copy so we can mutate
+				newRef.Subject = tr.Phase(addrs.ResourceInstancePhaseDestroy)
+				newRef.Remaining = nil // can't access attributes of something being destroyed
+				ret = append(ret, &newRef)
+			case addrs.Resource:
+				// We'll guess that this is actually a reference to a no-key
+				// instance here, and generate a reference under that assumption.
+				// If that's not true then this won't do any harm, since there
+				// won't actually be a node with this address.
+				newRef := *ref // shallow copy so we can mutate
+				newRef.Subject = tr.Instance(addrs.NoKey).Phase(addrs.ResourceInstancePhaseDestroy)
+				newRef.Remaining = nil // can't access attributes of something being destroyed
+				ret = append(ret, &newRef)
+			}
 		}
 	}
 
-	return result
+	return nil
 }
 
 // GraphNodeEvalable
-func (n *NodeApplyableResource) EvalTree() EvalNode {
-	addr := n.NodeAbstractResource.Addr
+func (n *NodeApplyableResourceInstance) EvalTree() EvalNode {
+	addr := n.ResourceInstanceAddr()
 
-	// stateId is the ID to put into the state
-	stateId := addr.stateId()
-
-	// Build the instance info. More of this will be populated during eval
-	info := &InstanceInfo{
-		Id:   stateId,
-		Type: addr.Type,
-	}
-
-	// Build the resource for eval
-	resource := &Resource{
-		Name:       addr.Name,
-		Type:       addr.Type,
-		CountIndex: addr.Index,
-	}
-	if resource.CountIndex < 0 {
-		resource.CountIndex = 0
-	}
+	// State still uses legacy-style internal ids, so we need to shim to get
+	// a suitable key to use.
+	stateId := NewLegacyResourceInstanceAddress(addr).stateId()
 
 	// Determine the dependencies for the state.
 	stateDeps := n.StateReferences()
 
 	// Eval info is different depending on what kind of resource this is
 	switch n.Config.Mode {
-	case config.ManagedResourceMode:
-		return n.evalTreeManagedResource(
-			stateId, info, resource, stateDeps,
-		)
-	case config.DataResourceMode:
-		return n.evalTreeDataResource(
-			stateId, info, resource, stateDeps)
+	case addrs.ManagedResourceMode:
+		return n.evalTreeManagedResource(addr, stateId, stateDeps)
+	case addrs.DataResourceMode:
+		return n.evalTreeDataResource(addr, stateId, stateDeps)
 	default:
 		panic(fmt.Errorf("unsupported resource mode %s", n.Config.Mode))
 	}
 }
 
-func (n *NodeApplyableResource) evalTreeDataResource(
-	stateId string, info *InstanceInfo,
-	resource *Resource, stateDeps []string) EvalNode {
+func (n *NodeApplyableResourceInstance) evalTreeDataResource(addr addrs.AbsResourceInstance, stateId string, stateDeps []string) EvalNode {
 	var provider ResourceProvider
-	var config *ResourceConfig
+	var providerSchema *ProviderSchema
 	var diff *InstanceDiff
 	var state *InstanceState
+	var configVal cty.Value
 
 	return &EvalSequence{
 		Nodes: []EvalNode{
-			// Build the instance info
-			&EvalInstanceInfo{
-				Info: info,
-			},
-
 			// Get the saved diff for apply
 			&EvalReadDiff{
 				Name: stateId,
 				Diff: &diff,
 			},
 
-			// Stop here if we don't actually have a diff
+			// Stop early if we don't actually have a diff
 			&EvalIf{
 				If: func(ctx EvalContext) (bool, error) {
 					if diff == nil {
@@ -124,53 +120,26 @@ func (n *NodeApplyableResource) evalTreeDataResource(
 				Then: EvalNoop{},
 			},
 
-			// Normally we interpolate count as a preparation step before
-			// a DynamicExpand, but an apply graph has pre-expanded nodes
-			// and so the count would otherwise never be interpolated.
-			//
-			// This is redundant when there are multiple instances created
-			// from the same config (count > 1) but harmless since the
-			// underlying structures have mutexes to make this concurrency-safe.
-			//
-			// In most cases this isn't actually needed because we dealt with
-			// all of the counts during the plan walk, but we do it here
-			// for completeness because other code assumes that the
-			// final count is always available during interpolation.
-			//
-			// Here we are just populating the interpolated value in-place
-			// inside this RawConfig object, like we would in
-			// NodeAbstractCountResource.
-			&EvalInterpolate{
-				Config:        n.Config.RawCount,
-				ContinueOnErr: true,
-			},
-
-			// We need to re-interpolate the config here, rather than
-			// just using the diff's values directly, because we've
-			// potentially learned more variable values during the
-			// apply pass that weren't known when the diff was produced.
-			&EvalInterpolate{
-				Config:   n.Config.RawConfig.Copy(),
-				Resource: resource,
-				Output:   &config,
-			},
-
 			&EvalGetProvider{
-				Name:   n.ResolvedProvider,
+				Addr:   n.ResolvedProvider,
 				Output: &provider,
+				Schema: &providerSchema,
 			},
 
-			// Make a new diff with our newly-interpolated config.
+			// Make a new diff, in case we've learned new values in the state
+			// during apply which we can now incorporate.
 			&EvalReadDataDiff{
-				Info:     info,
-				Config:   &config,
-				Previous: &diff,
-				Provider: &provider,
-				Output:   &diff,
+				Addr:           addr.Resource,
+				Config:         n.Config,
+				Provider:       &provider,
+				ProviderSchema: &providerSchema,
+				Output:         &diff,
+				OutputValue:    &configVal,
+				OutputState:    &state,
 			},
 
 			&EvalReadDataApply{
-				Info:     info,
+				Addr:     addr.Resource,
 				Diff:     &diff,
 				Provider: &provider,
 				Output:   &state,
@@ -196,26 +165,20 @@ func (n *NodeApplyableResource) evalTreeDataResource(
 	}
 }
 
-func (n *NodeApplyableResource) evalTreeManagedResource(
-	stateId string, info *InstanceInfo,
-	resource *Resource, stateDeps []string) EvalNode {
+func (n *NodeApplyableResourceInstance) evalTreeManagedResource(addr addrs.AbsResourceInstance, stateId string, stateDeps []string) EvalNode {
 	// Declare a bunch of variables that are used for state during
 	// evaluation. Most of this are written to by-address below.
 	var provider ResourceProvider
+	var providerSchema *ProviderSchema
 	var diff, diffApply *InstanceDiff
 	var state *InstanceState
-	var resourceConfig *ResourceConfig
 	var err error
 	var createNew bool
 	var createBeforeDestroyEnabled bool
+	var configVal cty.Value
 
 	return &EvalSequence{
 		Nodes: []EvalNode{
-			// Build the instance info
-			&EvalInstanceInfo{
-				Info: info,
-			},
-
 			// Get the saved diff for apply
 			&EvalReadDiff{
 				Name: stateId,
@@ -223,6 +186,7 @@ func (n *NodeApplyableResource) evalTreeManagedResource(
 			},
 
 			// We don't want to do any destroys
+			// (these are handled by NodeDestroyResourceInstance instead)
 			&EvalIf{
 				If: func(ctx EvalContext) (bool, error) {
 					if diffApply == nil {
@@ -246,9 +210,9 @@ func (n *NodeApplyableResource) evalTreeManagedResource(
 						destroy = diffApply.GetDestroy() || diffApply.RequiresNew()
 					}
 
-					createBeforeDestroyEnabled =
-						n.Config.Lifecycle.CreateBeforeDestroy &&
-							destroy
+					if destroy && n.Config.Managed != nil && n.Config.Managed.CreateBeforeDestroy {
+						createBeforeDestroyEnabled = true
+					}
 
 					return createBeforeDestroyEnabled, nil
 				},
@@ -257,59 +221,27 @@ func (n *NodeApplyableResource) evalTreeManagedResource(
 				},
 			},
 
-			// Normally we interpolate count as a preparation step before
-			// a DynamicExpand, but an apply graph has pre-expanded nodes
-			// and so the count would otherwise never be interpolated.
-			//
-			// This is redundant when there are multiple instances created
-			// from the same config (count > 1) but harmless since the
-			// underlying structures have mutexes to make this concurrency-safe.
-			//
-			// In most cases this isn't actually needed because we dealt with
-			// all of the counts during the plan walk, but we need to do this
-			// in order to support interpolation of resource counts from
-			// apply-time-interpolated expressions, such as those in
-			// "provisioner" blocks.
-			//
-			// Here we are just populating the interpolated value in-place
-			// inside this RawConfig object, like we would in
-			// NodeAbstractCountResource.
-			&EvalInterpolate{
-				Config:        n.Config.RawCount,
-				ContinueOnErr: true,
-			},
-
-			&EvalInterpolate{
-				Config:   n.Config.RawConfig.Copy(),
-				Resource: resource,
-				Output:   &resourceConfig,
-			},
 			&EvalGetProvider{
-				Name:   n.ResolvedProvider,
+				Addr:   n.ResolvedProvider,
 				Output: &provider,
+				Schema: &providerSchema,
 			},
 			&EvalReadState{
 				Name:   stateId,
 				Output: &state,
 			},
-			// Re-run validation to catch any errors we missed, e.g. type
-			// mismatches on computed values.
-			&EvalValidateResource{
-				Provider:       &provider,
-				Config:         &resourceConfig,
-				ResourceName:   n.Config.Name,
-				ResourceType:   n.Config.Type,
-				ResourceMode:   n.Config.Mode,
-				IgnoreWarnings: true,
-			},
+
+			// Make a new diff, in case we've learned new values in the state
+			// during apply which we can now incorporate.
 			&EvalDiff{
-				Info:       info,
-				Config:     &resourceConfig,
-				Resource:   n.Config,
-				Provider:   &provider,
-				Diff:       &diffApply,
-				State:      &state,
-				OutputDiff: &diffApply,
+				Addr:           addr.Resource,
+				Config:         n.Config,
+				Provider:       &provider,
+				ProviderSchema: &providerSchema,
+				State:          &state,
+				OutputDiff:     &diffApply,
+				OutputValue:    &configVal,
+				OutputState:    &state,
 			},
 
 			// Get the saved diff
@@ -320,27 +252,29 @@ func (n *NodeApplyableResource) evalTreeManagedResource(
 
 			// Compare the diffs
 			&EvalCompareDiff{
-				Info: info,
+				Addr: addr.Resource,
 				One:  &diff,
 				Two:  &diffApply,
 			},
 
 			&EvalGetProvider{
-				Name:   n.ResolvedProvider,
+				Addr:   n.ResolvedProvider,
 				Output: &provider,
+				Schema: &providerSchema,
 			},
 			&EvalReadState{
 				Name:   stateId,
 				Output: &state,
 			},
+
 			// Call pre-apply hook
 			&EvalApplyPre{
-				Info:  info,
+				Addr:  addr.Resource,
 				State: &state,
 				Diff:  &diffApply,
 			},
 			&EvalApply{
-				Info:      info,
+				Addr:      addr.Resource,
 				State:     &state,
 				Diff:      &diffApply,
 				Provider:  &provider,
@@ -356,13 +290,12 @@ func (n *NodeApplyableResource) evalTreeManagedResource(
 				State:        &state,
 			},
 			&EvalApplyProvisioners{
-				Info:           info,
+				Addr:           addr.Resource,
 				State:          &state,
-				Resource:       n.Config,
-				InterpResource: resource,
+				ResourceConfig: n.Config,
 				CreateNew:      &createNew,
 				Error:          &err,
-				When:           config.ProvisionerWhenCreate,
+				When:           configs.ProvisionerWhenCreate,
 			},
 			&EvalIf{
 				If: func(ctx EvalContext) (bool, error) {
@@ -390,7 +323,7 @@ func (n *NodeApplyableResource) evalTreeManagedResource(
 			},
 
 			&EvalApplyPost{
-				Info:  info,
+				Addr:  addr.Resource,
 				State: &state,
 				Error: &err,
 			},

terraform/node_resource_destroy.go

@@ -1,82 +1,90 @@
 package terraform
 
 import (
-	"fmt"
-
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
 )
 
 // NodeDestroyResource represents a resource that is to be destroyed.
-type NodeDestroyResource struct {
-	*NodeAbstractResource
+type NodeDestroyResourceInstance struct {
+	*NodeAbstractResourceInstance
+
+	CreateBeforeDestroyOverride *bool
 }
 
-func (n *NodeDestroyResource) Name() string {
-	return n.NodeAbstractResource.Name() + " (destroy)"
+var (
+	_ GraphNodeResource            = (*NodeDestroyResourceInstance)(nil)
+	_ GraphNodeResourceInstance    = (*NodeDestroyResourceInstance)(nil)
+	_ GraphNodeDestroyer           = (*NodeDestroyResourceInstance)(nil)
+	_ GraphNodeDestroyerCBD        = (*NodeDestroyResourceInstance)(nil)
+	_ GraphNodeReferenceable       = (*NodeDestroyResourceInstance)(nil)
+	_ GraphNodeReferencer          = (*NodeDestroyResourceInstance)(nil)
+	_ GraphNodeEvalable            = (*NodeDestroyResourceInstance)(nil)
+	_ GraphNodeProviderConsumer    = (*NodeDestroyResourceInstance)(nil)
+	_ GraphNodeProvisionerConsumer = (*NodeDestroyResourceInstance)(nil)
+)
+
+func (n *NodeDestroyResourceInstance) Name() string {
+	return n.ResourceInstanceAddr().String() + " (destroy)"
 }
 
 // GraphNodeDestroyer
-func (n *NodeDestroyResource) DestroyAddr() *ResourceAddress {
-	return n.Addr
+func (n *NodeDestroyResourceInstance) DestroyAddr() *addrs.AbsResourceInstance {
+	addr := n.ResourceInstanceAddr()
+	return &addr
 }
 
 // GraphNodeDestroyerCBD
-func (n *NodeDestroyResource) CreateBeforeDestroy() bool {
+func (n *NodeDestroyResourceInstance) CreateBeforeDestroy() bool {
+	if n.CreateBeforeDestroyOverride != nil {
+		return *n.CreateBeforeDestroyOverride
+	}
+
 	// If we have no config, we just assume no
-	if n.Config == nil {
+	if n.Config == nil || n.Config.Managed == nil {
 		return false
 	}
 
-	return n.Config.Lifecycle.CreateBeforeDestroy
+	return n.Config.Managed.CreateBeforeDestroy
 }
 
 // GraphNodeDestroyerCBD
-func (n *NodeDestroyResource) ModifyCreateBeforeDestroy(v bool) error {
-	// If we have no config, do nothing since it won't affect the
-	// create step anyways.
-	if n.Config == nil {
-		return nil
-	}
-
-	// Set CBD to true
-	n.Config.Lifecycle.CreateBeforeDestroy = true
-
+func (n *NodeDestroyResourceInstance) ModifyCreateBeforeDestroy(v bool) error {
+	n.CreateBeforeDestroyOverride = &v
 	return nil
 }
 
 // GraphNodeReferenceable, overriding NodeAbstractResource
-func (n *NodeDestroyResource) ReferenceableName() []string {
-	// We modify our referenceable name to have the suffix of ".destroy"
-	// since depending on the creation side doesn't necessarilly mean
-	// depending on destruction.
-	suffix := ".destroy"
-
-	// If we're CBD, we also append "-cbd". This is because CBD will setup
-	// its own edges (in CBDEdgeTransformer). Depending on the "destroy"
-	// side generally doesn't mean depending on CBD as well. See GH-11349
-	if n.CreateBeforeDestroy() {
-		suffix += "-cbd"
+func (n *NodeDestroyResourceInstance) ReferenceableName() []addrs.Referenceable {
+	relAddr := n.ResourceInstanceAddr().Resource
+	switch {
+	case n.CreateBeforeDestroy():
+		return []addrs.Referenceable{
+			relAddr.ContainingResource(),
+			relAddr.Phase(addrs.ResourceInstancePhaseDestroyCBD),
+		}
+	default:
+		return []addrs.Referenceable{
+			relAddr.ContainingResource(),
+			relAddr.Phase(addrs.ResourceInstancePhaseDestroy),
+		}
 	}
-
-	result := n.NodeAbstractResource.ReferenceableName()
-	for i, v := range result {
-		result[i] = v + suffix
-	}
-
-	return result
 }
 
 // GraphNodeReferencer, overriding NodeAbstractResource
-func (n *NodeDestroyResource) References() []string {
+func (n *NodeDestroyResourceInstance) References() []*addrs.Reference {
 	// If we have a config, then we need to include destroy-time dependencies
-	if c := n.Config; c != nil {
-		var result []string
-		for _, p := range c.Provisioners {
-			// We include conn info and config for destroy time provisioners
-			// as dependencies that we have.
-			if p.When == config.ProvisionerWhenDestroy {
-				result = append(result, ReferencesFromConfig(p.ConnInfo)...)
-				result = append(result, ReferencesFromConfig(p.RawConfig)...)
+	if c := n.Config; c != nil && c.Managed != nil {
+		var result []*addrs.Reference
+
+		// We include conn info and config for destroy time provisioners
+		// as dependencies that we have.
+		for _, p := range c.Managed.Provisioners {
+			schema := n.ProvisionerSchemas[p.Type]
+
+			if p.When == configs.ProvisionerWhenDestroy {
+				result = append(result, ReferencesFromConfig(p.Connection.Config, connectionBlockSupersetSchema)...)
+				result = append(result, ReferencesFromConfig(p.Config, schema)...)
 			}
 		}
 
@@ -87,11 +95,9 @@ func (n *NodeDestroyResource) References() []string {
 }
 
 // GraphNodeDynamicExpandable
-func (n *NodeDestroyResource) DynamicExpand(ctx EvalContext) (*Graph, error) {
-	// If we have no config we do nothing
-	if n.Addr == nil {
-		return nil, nil
-	}
+func (n *NodeDestroyResourceInstance) DynamicExpand(ctx EvalContext) (*Graph, error) {
+	// stateId is the legacy-style ID to put into the state
+	stateId := NewLegacyResourceInstanceAddress(n.ResourceInstanceAddr()).stateId()
 
 	state, lock := ctx.State()
 	lock.RLock()
@@ -103,13 +109,13 @@ func (n *NodeDestroyResource) DynamicExpand(ctx EvalContext) (*Graph, error) {
 	// We want deposed resources in the state to be destroyed
 	steps = append(steps, &DeposedTransformer{
 		State:            state,
-		View:             n.Addr.stateId(),
+		View:             stateId,
 		ResolvedProvider: n.ResolvedProvider,
 	})
 
 	// Target
 	steps = append(steps, &TargetsTransformer{
-		ParsedTargets: n.Targets,
+		Targets: n.Targets,
 	})
 
 	// Always end with the root being added
@@ -120,37 +126,22 @@ func (n *NodeDestroyResource) DynamicExpand(ctx EvalContext) (*Graph, error) {
 		Steps: steps,
 		Name:  "NodeResourceDestroy",
 	}
-	return b.Build(ctx.Path())
+	g, diags := b.Build(ctx.Path())
+	return g, diags.ErrWithWarnings()
 }
 
 // GraphNodeEvalable
-func (n *NodeDestroyResource) EvalTree() EvalNode {
-	// stateId is the ID to put into the state
-	stateId := n.Addr.stateId()
+func (n *NodeDestroyResourceInstance) EvalTree() EvalNode {
+	addr := n.ResourceInstanceAddr()
 
-	// Build the instance info. More of this will be populated during eval
-	info := &InstanceInfo{
-		Id:          stateId,
-		Type:        n.Addr.Type,
-		uniqueExtra: "destroy",
-	}
-
-	// Build the resource for eval
-	addr := n.Addr
-	resource := &Resource{
-		Name:       addr.Name,
-		Type:       addr.Type,
-		CountIndex: addr.Index,
-	}
-	if resource.CountIndex < 0 {
-		resource.CountIndex = 0
-	}
+	// stateId is the legacy-style ID to put into the state
+	stateId := NewLegacyResourceInstanceAddress(n.ResourceInstanceAddr()).stateId()
 
 	// Get our state
 	rs := n.ResourceState
 	if rs == nil {
 		rs = &ResourceState{
-			Provider: n.ResolvedProvider,
+			Provider: n.ResolvedProvider.String(),
 		}
 	}
 
@@ -187,11 +178,8 @@ func (n *NodeDestroyResource) EvalTree() EvalNode {
 					Then: EvalNoop{},
 				},
 
-				// Load the instance info so we have the module path set
-				&EvalInstanceInfo{Info: info},
-
 				&EvalGetProvider{
-					Name:   n.ResolvedProvider,
+					Addr:   n.ResolvedProvider,
 					Output: &provider,
 				},
 				&EvalReadState{
@@ -204,7 +192,7 @@ func (n *NodeDestroyResource) EvalTree() EvalNode {
 
 				// Call pre-apply hook
 				&EvalApplyPre{
-					Info:  info,
+					Addr:  addr.Resource,
 					State: &state,
 					Diff:  &diffApply,
 				},
@@ -220,12 +208,11 @@ func (n *NodeDestroyResource) EvalTree() EvalNode {
 					},
 
 					Then: &EvalApplyProvisioners{
-						Info:           info,
+						Addr:           addr.Resource,
 						State:          &state,
-						Resource:       n.Config,
-						InterpResource: resource,
+						ResourceConfig: n.Config,
 						Error:          &err,
-						When:           config.ProvisionerWhenDestroy,
+						When:           configs.ProvisionerWhenDestroy,
 					},
 				},
 
@@ -237,7 +224,7 @@ func (n *NodeDestroyResource) EvalTree() EvalNode {
 					},
 
 					Then: &EvalApplyPost{
-						Info:  info,
+						Addr:  addr.Resource,
 						State: &state,
 						Error: &err,
 					},
@@ -246,25 +233,17 @@ func (n *NodeDestroyResource) EvalTree() EvalNode {
 				// Make sure we handle data sources properly.
 				&EvalIf{
 					If: func(ctx EvalContext) (bool, error) {
-						if n.Addr == nil {
-							return false, fmt.Errorf("nil address")
-						}
-
-						if n.Addr.Mode == config.DataResourceMode {
-							return true, nil
-						}
-
-						return false, nil
+						return addr.Resource.Resource.Mode == addrs.DataResourceMode, nil
 					},
 
 					Then: &EvalReadDataApply{
-						Info:     info,
+						Addr:     addr.Resource,
 						Diff:     &diffApply,
 						Provider: &provider,
 						Output:   &state,
 					},
 					Else: &EvalApply{
-						Info:     info,
+						Addr:     addr.Resource,
 						State:    &state,
 						Diff:     &diffApply,
 						Provider: &provider,
@@ -274,13 +253,13 @@ func (n *NodeDestroyResource) EvalTree() EvalNode {
 				},
 				&EvalWriteState{
 					Name:         stateId,
-					ResourceType: n.Addr.Type,
+					ResourceType: addr.Resource.Resource.Type,
 					Provider:     n.ResolvedProvider,
 					Dependencies: rs.Dependencies,
 					State:        &state,
 				},
 				&EvalApplyPost{
-					Info:  info,
+					Addr:  addr.Resource,
 					State: &state,
 					Error: &err,
 				},

terraform/node_resource_plan.go

@@ -2,46 +2,62 @@ package terraform
 
 import (
 	"github.com/hashicorp/terraform/dag"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // NodePlannableResource represents a resource that is "plannable":
 // it is ready to be planned in order to create a diff.
 type NodePlannableResource struct {
-	*NodeAbstractCountResource
+	*NodeAbstractResource
 }
 
+var (
+	_ GraphNodeSubPath              = (*NodePlannableResource)(nil)
+	_ GraphNodeDynamicExpandable    = (*NodePlannableResource)(nil)
+	_ GraphNodeReferenceable        = (*NodePlannableResource)(nil)
+	_ GraphNodeReferencer           = (*NodePlannableResource)(nil)
+	_ GraphNodeResource             = (*NodePlannableResource)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodePlannableResource)(nil)
+)
+
 // GraphNodeDynamicExpandable
 func (n *NodePlannableResource) DynamicExpand(ctx EvalContext) (*Graph, error) {
+	var diags tfdiags.Diagnostics
+
+	count, countDiags := evaluateResourceCountExpression(n.Config.Count, ctx)
+	diags = diags.Append(countDiags)
+	if countDiags.HasErrors() {
+		return nil, diags.Err()
+	}
+
+	// Next we need to potentially rename an instance address in the state
+	// if we're transitioning whether "count" is set at all.
+	fixResourceCountSetTransition(ctx, n.ResourceAddr().Resource, count != -1)
+
 	// Grab the state which we read
 	state, lock := ctx.State()
 	lock.RLock()
 	defer lock.RUnlock()
 
-	// Expand the resource count which must be available by now from EvalTree
-	count, err := n.Config.Count()
-	if err != nil {
-		return nil, err
-	}
-
 	// The concrete resource factory we'll use
-	concreteResource := func(a *NodeAbstractResource) dag.Vertex {
+	concreteResource := func(a *NodeAbstractResourceInstance) dag.Vertex {
 		// Add the config and state since we don't do that via transforms
 		a.Config = n.Config
 		a.ResolvedProvider = n.ResolvedProvider
 
 		return &NodePlannableResourceInstance{
-			NodeAbstractResource: a,
+			NodeAbstractResourceInstance: a,
 		}
 	}
 
-	// The concrete resource factory we'll use for oprhans
-	concreteResourceOrphan := func(a *NodeAbstractResource) dag.Vertex {
+	// The concrete resource factory we'll use for orphans
+	concreteResourceOrphan := func(a *NodeAbstractResourceInstance) dag.Vertex {
 		// Add the config and state since we don't do that via transforms
 		a.Config = n.Config
 		a.ResolvedProvider = n.ResolvedProvider
 
-		return &NodePlannableResourceOrphan{
-			NodeAbstractResource: a,
+		return &NodePlannableResourceInstanceOrphan{
+			NodeAbstractResourceInstance: a,
 		}
 	}
 
@@ -66,7 +82,7 @@ func (n *NodePlannableResource) DynamicExpand(ctx EvalContext) (*Graph, error) {
 		&AttachStateTransformer{State: state},
 
 		// Targeting
-		&TargetsTransformer{ParsedTargets: n.Targets},
+		&TargetsTransformer{Targets: n.Targets},
 
 		// Connect references so ordering is correct
 		&ReferenceTransformer{},
@@ -81,5 +97,6 @@ func (n *NodePlannableResource) DynamicExpand(ctx EvalContext) (*Graph, error) {
 		Validate: true,
 		Name:     "NodePlannableResource",
 	}
-	return b.Build(ctx.Path())
+	graph, diags := b.Build(ctx.Path())
+	return graph, diags.ErrWithWarnings()
 }

terraform/node_resource_plan_destroy.go

@@ -1,28 +1,40 @@
 package terraform
 
-// NodePlanDestroyableResource represents a resource that is "applyable":
-// it is ready to be applied and is represented by a diff.
-type NodePlanDestroyableResource struct {
-	*NodeAbstractResource
+import (
+	"github.com/hashicorp/terraform/addrs"
+)
+
+// NodePlanDestroyableResourceInstance represents a resource that is ready
+// to be planned for destruction.
+type NodePlanDestroyableResourceInstance struct {
+	*NodeAbstractResourceInstance
 }
 
+var (
+	_ GraphNodeSubPath              = (*NodePlanDestroyableResourceInstance)(nil)
+	_ GraphNodeReferenceable        = (*NodePlanDestroyableResourceInstance)(nil)
+	_ GraphNodeReferencer           = (*NodePlanDestroyableResourceInstance)(nil)
+	_ GraphNodeDestroyer            = (*NodePlanDestroyableResourceInstance)(nil)
+	_ GraphNodeResource             = (*NodePlanDestroyableResourceInstance)(nil)
+	_ GraphNodeResourceInstance     = (*NodePlanDestroyableResourceInstance)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodePlanDestroyableResourceInstance)(nil)
+	_ GraphNodeAttachResourceState  = (*NodePlanDestroyableResourceInstance)(nil)
+	_ GraphNodeEvalable             = (*NodePlanDestroyableResourceInstance)(nil)
+)
+
 // GraphNodeDestroyer
-func (n *NodePlanDestroyableResource) DestroyAddr() *ResourceAddress {
-	return n.Addr
+func (n *NodePlanDestroyableResourceInstance) DestroyAddr() *addrs.AbsResourceInstance {
+	addr := n.ResourceInstanceAddr()
+	return &addr
 }
 
 // GraphNodeEvalable
-func (n *NodePlanDestroyableResource) EvalTree() EvalNode {
-	addr := n.NodeAbstractResource.Addr
+func (n *NodePlanDestroyableResourceInstance) EvalTree() EvalNode {
+	addr := n.ResourceInstanceAddr()
 
-	// stateId is the ID to put into the state
-	stateId := addr.stateId()
-
-	// Build the instance info. More of this will be populated during eval
-	info := &InstanceInfo{
-		Id:   stateId,
-		Type: addr.Type,
-	}
+	// State still uses legacy-style internal ids, so we need to shim to get
+	// a suitable key to use.
+	stateId := NewLegacyResourceInstanceAddress(addr).stateId()
 
 	// Declare a bunch of variables that are used for state during
 	// evaluation. Most of this are written to by-address below.
@@ -36,13 +48,14 @@ func (n *NodePlanDestroyableResource) EvalTree() EvalNode {
 				Output: &state,
 			},
 			&EvalDiffDestroy{
-				Info:   info,
+				Addr:   addr.Resource,
 				State:  &state,
 				Output: &diff,
 			},
 			&EvalCheckPreventDestroy{
-				Resource: n.Config,
-				Diff:     &diff,
+				Addr:   addr.Resource,
+				Config: n.Config,
+				Diff:   &diff,
 			},
 			&EvalWriteDiff{
 				Name: stateId,

terraform/node_resource_plan_instance.go

@@ -3,64 +3,56 @@ package terraform
 import (
 	"fmt"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/zclconf/go-cty/cty"
 )
 
 // NodePlannableResourceInstance represents a _single_ resource
 // instance that is plannable. This means this represents a single
 // count index, for example.
 type NodePlannableResourceInstance struct {
-	*NodeAbstractResource
+	*NodeAbstractResourceInstance
 }
 
+var (
+	_ GraphNodeSubPath              = (*NodePlannableResourceInstance)(nil)
+	_ GraphNodeReferenceable        = (*NodePlannableResourceInstance)(nil)
+	_ GraphNodeReferencer           = (*NodePlannableResourceInstance)(nil)
+	_ GraphNodeResource             = (*NodePlannableResourceInstance)(nil)
+	_ GraphNodeResourceInstance     = (*NodePlannableResourceInstance)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodePlannableResourceInstance)(nil)
+	_ GraphNodeAttachResourceState  = (*NodePlannableResourceInstance)(nil)
+	_ GraphNodeEvalable             = (*NodePlannableResourceInstance)(nil)
+)
+
 // GraphNodeEvalable
 func (n *NodePlannableResourceInstance) EvalTree() EvalNode {
-	addr := n.NodeAbstractResource.Addr
+	addr := n.ResourceInstanceAddr()
 
-	// stateId is the ID to put into the state
-	stateId := addr.stateId()
-
-	// Build the instance info. More of this will be populated during eval
-	info := &InstanceInfo{
-		Id:         stateId,
-		Type:       addr.Type,
-		ModulePath: normalizeModulePath(addr.Path),
-	}
-
-	// Build the resource for eval
-	resource := &Resource{
-		Name:       addr.Name,
-		Type:       addr.Type,
-		CountIndex: addr.Index,
-	}
-	if resource.CountIndex < 0 {
-		resource.CountIndex = 0
-	}
+	// State still uses legacy-style internal ids, so we need to shim to get
+	// a suitable key to use.
+	stateId := NewLegacyResourceInstanceAddress(addr).stateId()
 
 	// Determine the dependencies for the state.
 	stateDeps := n.StateReferences()
 
 	// Eval info is different depending on what kind of resource this is
-	switch n.Config.Mode {
-	case config.ManagedResourceMode:
-		return n.evalTreeManagedResource(
-			stateId, info, resource, stateDeps,
-		)
-	case config.DataResourceMode:
-		return n.evalTreeDataResource(
-			stateId, info, resource, stateDeps)
+	switch addr.Resource.Resource.Mode {
+	case addrs.ManagedResourceMode:
+		return n.evalTreeManagedResource(addr, stateId, stateDeps)
+	case addrs.DataResourceMode:
+		return n.evalTreeDataResource(addr, stateId, stateDeps)
 	default:
 		panic(fmt.Errorf("unsupported resource mode %s", n.Config.Mode))
 	}
 }
 
-func (n *NodePlannableResourceInstance) evalTreeDataResource(
-	stateId string, info *InstanceInfo,
-	resource *Resource, stateDeps []string) EvalNode {
+func (n *NodePlannableResourceInstance) evalTreeDataResource(addr addrs.AbsResourceInstance, stateId string, stateDeps []string) EvalNode {
 	var provider ResourceProvider
-	var config *ResourceConfig
+	var providerSchema *ProviderSchema
 	var diff *InstanceDiff
 	var state *InstanceState
+	var configVal cty.Value
 
 	return &EvalSequence{
 		Nodes: []EvalNode{
@@ -69,19 +61,25 @@ func (n *NodePlannableResourceInstance) evalTreeDataResource(
 				Output: &state,
 			},
 
-			// We need to re-interpolate the config here because some
-			// of the attributes may have become computed during
-			// earlier planning, due to other resources having
-			// "requires new resource" diffs.
-			&EvalInterpolate{
-				Config:   n.Config.RawConfig.Copy(),
-				Resource: resource,
-				Output:   &config,
+			&EvalGetProvider{
+				Addr:   n.ResolvedProvider,
+				Output: &provider,
+				Schema: &providerSchema,
+			},
+
+			&EvalReadDataDiff{
+				Addr:           addr.Resource,
+				Config:         n.Config,
+				Provider:       &provider,
+				ProviderSchema: &providerSchema,
+				Output:         &diff,
+				OutputValue:    &configVal,
+				OutputState:    &state,
 			},
 
 			&EvalIf{
 				If: func(ctx EvalContext) (bool, error) {
-					computed := config.ComputedKeys != nil && len(config.ComputedKeys) > 0
+					computed := !configVal.IsWhollyKnown()
 
 					// If the configuration is complete and we
 					// already have a state then we don't need to
@@ -96,19 +94,6 @@ func (n *NodePlannableResourceInstance) evalTreeDataResource(
 				Then: EvalNoop{},
 			},
 
-			&EvalGetProvider{
-				Name:   n.ResolvedProvider,
-				Output: &provider,
-			},
-
-			&EvalReadDataDiff{
-				Info:        info,
-				Config:      &config,
-				Provider:    &provider,
-				Output:      &diff,
-				OutputState: &state,
-			},
-
 			&EvalWriteState{
 				Name:         stateId,
 				ResourceType: n.Config.Type,
@@ -125,54 +110,38 @@ func (n *NodePlannableResourceInstance) evalTreeDataResource(
 	}
 }
 
-func (n *NodePlannableResourceInstance) evalTreeManagedResource(
-	stateId string, info *InstanceInfo,
-	resource *Resource, stateDeps []string) EvalNode {
-	// Declare a bunch of variables that are used for state during
-	// evaluation. Most of this are written to by-address below.
+func (n *NodePlannableResourceInstance) evalTreeManagedResource(addr addrs.AbsResourceInstance, stateId string, stateDeps []string) EvalNode {
 	var provider ResourceProvider
+	var providerSchema *ProviderSchema
 	var diff *InstanceDiff
 	var state *InstanceState
-	var resourceConfig *ResourceConfig
 
 	return &EvalSequence{
 		Nodes: []EvalNode{
-			&EvalInterpolate{
-				Config:   n.Config.RawConfig.Copy(),
-				Resource: resource,
-				Output:   &resourceConfig,
-			},
-			&EvalGetProvider{
-				Name:   n.ResolvedProvider,
-				Output: &provider,
-			},
-			// Re-run validation to catch any errors we missed, e.g. type
-			// mismatches on computed values.
-			&EvalValidateResource{
-				Provider:       &provider,
-				Config:         &resourceConfig,
-				ResourceName:   n.Config.Name,
-				ResourceType:   n.Config.Type,
-				ResourceMode:   n.Config.Mode,
-				IgnoreWarnings: true,
-			},
 			&EvalReadState{
 				Name:   stateId,
 				Output: &state,
 			},
+
+			&EvalGetProvider{
+				Addr:   n.ResolvedProvider,
+				Output: &provider,
+				Schema: &providerSchema,
+			},
+
 			&EvalDiff{
-				Name:        stateId,
-				Info:        info,
-				Config:      &resourceConfig,
-				Resource:    n.Config,
-				Provider:    &provider,
-				State:       &state,
-				OutputDiff:  &diff,
-				OutputState: &state,
+				Addr:           addr.Resource,
+				Config:         n.Config,
+				Provider:       &provider,
+				ProviderSchema: &providerSchema,
+				State:          &state,
+				OutputDiff:     &diff,
+				OutputState:    &state,
 			},
 			&EvalCheckPreventDestroy{
-				Resource: n.Config,
-				Diff:     &diff,
+				Addr:   addr.Resource,
+				Config: n.Config,
+				Diff:   &diff,
 			},
 			&EvalWriteState{
 				Name:         stateId,

terraform/node_resource_plan_orphan.go

@@ -1,28 +1,37 @@
 package terraform
 
-// NodePlannableResourceOrphan represents a resource that is "applyable":
+// NodePlannableResourceInstanceOrphan represents a resource that is "applyable":
 // it is ready to be applied and is represented by a diff.
-type NodePlannableResourceOrphan struct {
-	*NodeAbstractResource
+type NodePlannableResourceInstanceOrphan struct {
+	*NodeAbstractResourceInstance
 }
 
-func (n *NodePlannableResourceOrphan) Name() string {
-	return n.NodeAbstractResource.Name() + " (orphan)"
+var (
+	_ GraphNodeSubPath              = (*NodePlannableResourceInstanceOrphan)(nil)
+	_ GraphNodeReferenceable        = (*NodePlannableResourceInstanceOrphan)(nil)
+	_ GraphNodeReferencer           = (*NodePlannableResourceInstanceOrphan)(nil)
+	_ GraphNodeResource             = (*NodePlannableResourceInstanceOrphan)(nil)
+	_ GraphNodeResourceInstance     = (*NodePlannableResourceInstanceOrphan)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodePlannableResourceInstanceOrphan)(nil)
+	_ GraphNodeAttachResourceState  = (*NodePlannableResourceInstanceOrphan)(nil)
+	_ GraphNodeEvalable             = (*NodePlannableResourceInstanceOrphan)(nil)
+)
+
+var (
+	_ GraphNodeEvalable = (*NodePlannableResourceInstanceOrphan)(nil)
+)
+
+func (n *NodePlannableResourceInstanceOrphan) Name() string {
+	return n.ResourceInstanceAddr().String() + " (orphan)"
 }
 
 // GraphNodeEvalable
-func (n *NodePlannableResourceOrphan) EvalTree() EvalNode {
-	addr := n.NodeAbstractResource.Addr
+func (n *NodePlannableResourceInstanceOrphan) EvalTree() EvalNode {
+	addr := n.ResourceInstanceAddr()
 
-	// stateId is the ID to put into the state
-	stateId := addr.stateId()
-
-	// Build the instance info. More of this will be populated during eval
-	info := &InstanceInfo{
-		Id:         stateId,
-		Type:       addr.Type,
-		ModulePath: normalizeModulePath(addr.Path),
-	}
+	// State still uses legacy-style internal ids, so we need to shim to get
+	// a suitable key to use.
+	stateId := NewLegacyResourceInstanceAddress(addr).stateId()
 
 	// Declare a bunch of variables that are used for state during
 	// evaluation. Most of this are written to by-address below.
@@ -36,14 +45,14 @@ func (n *NodePlannableResourceOrphan) EvalTree() EvalNode {
 				Output: &state,
 			},
 			&EvalDiffDestroy{
-				Info:   info,
+				Addr:   addr.Resource,
 				State:  &state,
 				Output: &diff,
 			},
 			&EvalCheckPreventDestroy{
-				Resource:   n.Config,
-				ResourceId: stateId,
-				Diff:       &diff,
+				Addr:   addr.Resource,
+				Config: n.Config,
+				Diff:   &diff,
 			},
 			&EvalWriteDiff{
 				Name: stateId,

terraform/node_resource_refresh.go

@@ -3,37 +3,53 @@ package terraform
 import (
 	"fmt"
 
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/dag"
+	"github.com/hashicorp/terraform/tfdiags"
 )
 
 // NodeRefreshableManagedResource represents a resource that is expanabled into
 // NodeRefreshableManagedResourceInstance. Resource count orphans are also added.
 type NodeRefreshableManagedResource struct {
-	*NodeAbstractCountResource
+	*NodeAbstractResource
 }
 
+var (
+	_ GraphNodeSubPath              = (*NodeRefreshableManagedResource)(nil)
+	_ GraphNodeDynamicExpandable    = (*NodeRefreshableManagedResource)(nil)
+	_ GraphNodeReferenceable        = (*NodeRefreshableManagedResource)(nil)
+	_ GraphNodeReferencer           = (*NodeRefreshableManagedResource)(nil)
+	_ GraphNodeResource             = (*NodeRefreshableManagedResource)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodeRefreshableManagedResource)(nil)
+)
+
 // GraphNodeDynamicExpandable
 func (n *NodeRefreshableManagedResource) DynamicExpand(ctx EvalContext) (*Graph, error) {
+	var diags tfdiags.Diagnostics
+
+	count, countDiags := evaluateResourceCountExpression(n.Config.Count, ctx)
+	diags = diags.Append(countDiags)
+	if countDiags.HasErrors() {
+		return nil, diags.Err()
+	}
+
+	// Next we need to potentially rename an instance address in the state
+	// if we're transitioning whether "count" is set at all.
+	fixResourceCountSetTransition(ctx, n.ResourceAddr().Resource, count != -1)
+
 	// Grab the state which we read
 	state, lock := ctx.State()
 	lock.RLock()
 	defer lock.RUnlock()
 
-	// Expand the resource count which must be available by now from EvalTree
-	count, err := n.Config.Count()
-	if err != nil {
-		return nil, err
-	}
-
 	// The concrete resource factory we'll use
-	concreteResource := func(a *NodeAbstractResource) dag.Vertex {
+	concreteResource := func(a *NodeAbstractResourceInstance) dag.Vertex {
 		// Add the config and state since we don't do that via transforms
 		a.Config = n.Config
 		a.ResolvedProvider = n.ResolvedProvider
 
 		return &NodeRefreshableManagedResourceInstance{
-			NodeAbstractResource: a,
+			NodeAbstractResourceInstance: a,
 		}
 	}
 
@@ -59,7 +75,7 @@ func (n *NodeRefreshableManagedResource) DynamicExpand(ctx EvalContext) (*Graph,
 		&AttachStateTransformer{State: state},
 
 		// Targeting
-		&TargetsTransformer{ParsedTargets: n.Targets},
+		&TargetsTransformer{Targets: n.Targets},
 
 		// Connect references so ordering is correct
 		&ReferenceTransformer{},
@@ -75,61 +91,72 @@ func (n *NodeRefreshableManagedResource) DynamicExpand(ctx EvalContext) (*Graph,
 		Name:     "NodeRefreshableManagedResource",
 	}
 
-	return b.Build(ctx.Path())
+	graph, diags := b.Build(ctx.Path())
+	return graph, diags.ErrWithWarnings()
 }
 
 // NodeRefreshableManagedResourceInstance represents a resource that is "applyable":
 // it is ready to be applied and is represented by a diff.
 type NodeRefreshableManagedResourceInstance struct {
-	*NodeAbstractResource
+	*NodeAbstractResourceInstance
 }
 
+var (
+	_ GraphNodeSubPath              = (*NodeRefreshableManagedResourceInstance)(nil)
+	_ GraphNodeReferenceable        = (*NodeRefreshableManagedResourceInstance)(nil)
+	_ GraphNodeReferencer           = (*NodeRefreshableManagedResourceInstance)(nil)
+	_ GraphNodeDestroyer            = (*NodeRefreshableManagedResourceInstance)(nil)
+	_ GraphNodeResource             = (*NodeRefreshableManagedResourceInstance)(nil)
+	_ GraphNodeResourceInstance     = (*NodeRefreshableManagedResourceInstance)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodeRefreshableManagedResourceInstance)(nil)
+	_ GraphNodeAttachResourceState  = (*NodeRefreshableManagedResourceInstance)(nil)
+	_ GraphNodeEvalable             = (*NodeRefreshableManagedResourceInstance)(nil)
+)
+
 // GraphNodeDestroyer
-func (n *NodeRefreshableManagedResourceInstance) DestroyAddr() *ResourceAddress {
-	return n.Addr
+func (n *NodeRefreshableManagedResourceInstance) DestroyAddr() *addrs.AbsResourceInstance {
+	addr := n.ResourceInstanceAddr()
+	return &addr
 }
 
 // GraphNodeEvalable
 func (n *NodeRefreshableManagedResourceInstance) EvalTree() EvalNode {
+	addr := n.ResourceInstanceAddr()
+
 	// Eval info is different depending on what kind of resource this is
-	switch mode := n.Addr.Mode; mode {
-	case config.ManagedResourceMode:
+	switch addr.Resource.Resource.Mode {
+	case addrs.ManagedResourceMode:
 		if n.ResourceState == nil {
 			return n.evalTreeManagedResourceNoState()
 		}
 		return n.evalTreeManagedResource()
 
-	case config.DataResourceMode:
+	case addrs.DataResourceMode:
 		// Get the data source node. If we don't have a configuration
 		// then it is an orphan so we destroy it (remove it from the state).
 		var dn GraphNodeEvalable
 		if n.Config != nil {
 			dn = &NodeRefreshableDataResourceInstance{
-				NodeAbstractResource: n.NodeAbstractResource,
+				NodeAbstractResourceInstance: n.NodeAbstractResourceInstance,
 			}
 		} else {
 			dn = &NodeDestroyableDataResource{
-				NodeAbstractResource: n.NodeAbstractResource,
+				NodeAbstractResourceInstance: n.NodeAbstractResourceInstance,
 			}
 		}
 
 		return dn.EvalTree()
 	default:
-		panic(fmt.Errorf("unsupported resource mode %s", mode))
+		panic(fmt.Errorf("unsupported resource mode %s", addr.Resource.Resource.Mode))
 	}
 }
 
 func (n *NodeRefreshableManagedResourceInstance) evalTreeManagedResource() EvalNode {
-	addr := n.NodeAbstractResource.Addr
+	addr := n.ResourceInstanceAddr()
 
-	// stateId is the ID to put into the state
-	stateId := addr.stateId()
-
-	// Build the instance info. More of this will be populated during eval
-	info := &InstanceInfo{
-		Id:   stateId,
-		Type: addr.Type,
-	}
+	// State still uses legacy-style internal ids, so we need to shim to get
+	// a suitable key to use.
+	stateId := NewLegacyResourceInstanceAddress(addr).stateId()
 
 	// Declare a bunch of variables that are used for state during
 	// evaluation. Most of this are written to by-address below.
@@ -149,20 +176,23 @@ func (n *NodeRefreshableManagedResourceInstance) evalTreeManagedResource() EvalN
 
 	return &EvalSequence{
 		Nodes: []EvalNode{
-			&EvalGetProvider{
-				Name:   n.ResolvedProvider,
-				Output: &provider,
-			},
 			&EvalReadState{
 				Name:   stateId,
 				Output: &state,
 			},
+
+			&EvalGetProvider{
+				Addr:   n.ResolvedProvider,
+				Output: &provider,
+			},
+
 			&EvalRefresh{
-				Info:     info,
+				Addr:     addr.Resource,
 				Provider: &provider,
 				State:    &state,
 				Output:   &state,
 			},
+
 			&EvalWriteState{
 				Name:         stateId,
 				ResourceType: n.ResourceState.Type,
@@ -186,74 +216,46 @@ func (n *NodeRefreshableManagedResourceInstance) evalTreeManagedResource() EvalN
 // plan, but nothing is done with the diff after it is created - it is dropped,
 // and its changes are not counted in the UI.
 func (n *NodeRefreshableManagedResourceInstance) evalTreeManagedResourceNoState() EvalNode {
+	addr := n.ResourceInstanceAddr()
+
 	// Declare a bunch of variables that are used for state during
 	// evaluation. Most of this are written to by-address below.
 	var provider ResourceProvider
+	var providerSchema *ProviderSchema
+	var diff *InstanceDiff
 	var state *InstanceState
-	var resourceConfig *ResourceConfig
 
-	addr := n.NodeAbstractResource.Addr
-	stateID := addr.stateId()
-	info := &InstanceInfo{
-		Id:         stateID,
-		Type:       addr.Type,
-		ModulePath: normalizeModulePath(addr.Path),
-	}
-
-	// Build the resource for eval
-	resource := &Resource{
-		Name:       addr.Name,
-		Type:       addr.Type,
-		CountIndex: addr.Index,
-	}
-	if resource.CountIndex < 0 {
-		resource.CountIndex = 0
-	}
+	// State still uses legacy-style internal ids, so we need to shim to get
+	// a suitable key to use.
+	stateID := NewLegacyResourceInstanceAddress(addr).stateId()
 
 	// Determine the dependencies for the state.
 	stateDeps := n.StateReferences()
 
-	// n.Config can be nil if the config and state don't match
-	var raw *config.RawConfig
-	if n.Config != nil {
-		raw = n.Config.RawConfig.Copy()
-	}
-
 	return &EvalSequence{
 		Nodes: []EvalNode{
-			&EvalInterpolate{
-				Config:   raw,
-				Resource: resource,
-				Output:   &resourceConfig,
-			},
-			&EvalGetProvider{
-				Name:   n.ResolvedProvider,
-				Output: &provider,
-			},
-			// Re-run validation to catch any errors we missed, e.g. type
-			// mismatches on computed values.
-			&EvalValidateResource{
-				Provider:       &provider,
-				Config:         &resourceConfig,
-				ResourceName:   n.Config.Name,
-				ResourceType:   n.Config.Type,
-				ResourceMode:   n.Config.Mode,
-				IgnoreWarnings: true,
-			},
 			&EvalReadState{
 				Name:   stateID,
 				Output: &state,
 			},
-			&EvalDiff{
-				Name:        stateID,
-				Info:        info,
-				Config:      &resourceConfig,
-				Resource:    n.Config,
-				Provider:    &provider,
-				State:       &state,
-				OutputState: &state,
-				Stub:        true,
+
+			&EvalGetProvider{
+				Addr:   n.ResolvedProvider,
+				Output: &provider,
+				Schema: &providerSchema,
 			},
+
+			&EvalDiff{
+				Addr:           addr.Resource,
+				Config:         n.Config,
+				Provider:       &provider,
+				ProviderSchema: &providerSchema,
+				State:          &state,
+				OutputDiff:     &diff,
+				OutputState:    &state,
+				Stub:           true,
+			},
+
 			&EvalWriteState{
 				Name:         stateID,
 				ResourceType: n.Config.Type,

terraform/node_resource_validate.go

@@ -1,48 +1,62 @@
 package terraform
 
 import (
+	"log"
+
+	"github.com/hashicorp/terraform/config/configschema"
 	"github.com/hashicorp/terraform/dag"
+	"github.com/hashicorp/terraform/tfdiags"
+	"github.com/zclconf/go-cty/cty"
 )
 
 // NodeValidatableResource represents a resource that is used for validation
 // only.
 type NodeValidatableResource struct {
-	*NodeAbstractCountResource
+	*NodeAbstractResource
 }
 
-// GraphNodeEvalable
-func (n *NodeValidatableResource) EvalTree() EvalNode {
-	// Ensure we're validating
-	c := n.NodeAbstractCountResource
-	c.Validate = true
-	return c.EvalTree()
-}
+var (
+	_ GraphNodeSubPath              = (*NodeValidatableResource)(nil)
+	_ GraphNodeDynamicExpandable    = (*NodeValidatableResource)(nil)
+	_ GraphNodeReferenceable        = (*NodeValidatableResource)(nil)
+	_ GraphNodeReferencer           = (*NodeValidatableResource)(nil)
+	_ GraphNodeResource             = (*NodeValidatableResource)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodeValidatableResource)(nil)
+)
 
 // GraphNodeDynamicExpandable
 func (n *NodeValidatableResource) DynamicExpand(ctx EvalContext) (*Graph, error) {
+	var diags tfdiags.Diagnostics
+
+	count, countDiags := evaluateResourceCountExpression(n.Config.Count, ctx)
+	diags = diags.Append(countDiags)
+	if countDiags.HasErrors() {
+		log.Printf("[TRACE] %T %s: count expression has errors", n, n.Name())
+		return nil, diags.Err()
+	}
+	if count >= 0 {
+		log.Printf("[TRACE] %T %s: count expression evaluates to %d", n, n.Name(), count)
+	} else {
+		log.Printf("[TRACE] %T %s: no count argument present", n, n.Name())
+	}
+
+	// Next we need to potentially rename an instance address in the state
+	// if we're transitioning whether "count" is set at all.
+	fixResourceCountSetTransition(ctx, n.ResourceAddr().Resource, count != -1)
+
 	// Grab the state which we read
 	state, lock := ctx.State()
 	lock.RLock()
 	defer lock.RUnlock()
 
-	// Expand the resource count which must be available by now from EvalTree
-	count := 1
-	if n.Config.RawCount.Value() != unknownValue() {
-		var err error
-		count, err = n.Config.Count()
-		if err != nil {
-			return nil, err
-		}
-	}
-
 	// The concrete resource factory we'll use
-	concreteResource := func(a *NodeAbstractResource) dag.Vertex {
+	concreteResource := func(a *NodeAbstractResourceInstance) dag.Vertex {
 		// Add the config and state since we don't do that via transforms
 		a.Config = n.Config
 		a.ResolvedProvider = n.ResolvedProvider
 
 		return &NodeValidatableResourceInstance{
-			NodeAbstractResource: a,
+			NodeAbstractResourceInstance: a,
 		}
 	}
 
@@ -59,7 +73,7 @@ func (n *NodeValidatableResource) DynamicExpand(ctx EvalContext) (*Graph, error)
 		&AttachStateTransformer{State: state},
 
 		// Targeting
-		&TargetsTransformer{ParsedTargets: n.Targets},
+		&TargetsTransformer{Targets: n.Targets},
 
 		// Connect references so ordering is correct
 		&ReferenceTransformer{},
@@ -75,84 +89,79 @@ func (n *NodeValidatableResource) DynamicExpand(ctx EvalContext) (*Graph, error)
 		Name:     "NodeValidatableResource",
 	}
 
-	return b.Build(ctx.Path())
+	graph, diags := b.Build(ctx.Path())
+	return graph, diags.ErrWithWarnings()
 }
 
 // This represents a _single_ resource instance to validate.
 type NodeValidatableResourceInstance struct {
-	*NodeAbstractResource
+	*NodeAbstractResourceInstance
 }
 
+var (
+	_ GraphNodeSubPath              = (*NodeValidatableResourceInstance)(nil)
+	_ GraphNodeReferenceable        = (*NodeValidatableResourceInstance)(nil)
+	_ GraphNodeReferencer           = (*NodeValidatableResourceInstance)(nil)
+	_ GraphNodeResource             = (*NodeValidatableResourceInstance)(nil)
+	_ GraphNodeResourceInstance     = (*NodeValidatableResourceInstance)(nil)
+	_ GraphNodeAttachResourceConfig = (*NodeValidatableResourceInstance)(nil)
+	_ GraphNodeAttachResourceState  = (*NodeValidatableResourceInstance)(nil)
+	_ GraphNodeEvalable             = (*NodeValidatableResourceInstance)(nil)
+)
+
 // GraphNodeEvalable
 func (n *NodeValidatableResourceInstance) EvalTree() EvalNode {
-	addr := n.NodeAbstractResource.Addr
-
-	// Build the resource for eval
-	resource := &Resource{
-		Name:       addr.Name,
-		Type:       addr.Type,
-		CountIndex: addr.Index,
-	}
-	if resource.CountIndex < 0 {
-		resource.CountIndex = 0
-	}
+	addr := n.ResourceInstanceAddr()
+	config := n.Config
 
 	// Declare a bunch of variables that are used for state during
-	// evaluation. Most of this are written to by-address below.
-	var config *ResourceConfig
+	// evaluation. These are written to via pointers passed to the EvalNodes
+	// below.
 	var provider ResourceProvider
+	var providerSchema *ProviderSchema
+	var configVal cty.Value
 
 	seq := &EvalSequence{
 		Nodes: []EvalNode{
-			&EvalValidateResourceSelfRef{
-				Addr:   &addr,
-				Config: &n.Config.RawConfig,
+			&EvalValidateSelfRef{
+				Addr:   addr.Resource,
+				Config: config.Config,
 			},
 			&EvalGetProvider{
-				Name:   n.ResolvedProvider,
+				Addr:   n.ResolvedProvider,
 				Output: &provider,
-			},
-			&EvalInterpolate{
-				Config:   n.Config.RawConfig.Copy(),
-				Resource: resource,
-				Output:   &config,
+				Schema: &providerSchema,
 			},
 			&EvalValidateResource{
-				Provider:     &provider,
-				Config:       &config,
-				ResourceName: n.Config.Name,
-				ResourceType: n.Config.Type,
-				ResourceMode: n.Config.Mode,
+				Addr:           addr.Resource,
+				Provider:       &provider,
+				ProviderSchema: &providerSchema,
+				Config:         config,
+				ConfigVal:      &configVal,
 			},
 		},
 	}
 
-	// Validate all the provisioners
-	for _, p := range n.Config.Provisioners {
-		var provisioner ResourceProvisioner
-		var connConfig *ResourceConfig
-		seq.Nodes = append(
-			seq.Nodes,
-			&EvalGetProvisioner{
-				Name:   p.Type,
-				Output: &provisioner,
-			},
-			&EvalInterpolate{
-				Config:   p.RawConfig.Copy(),
-				Resource: resource,
-				Output:   &config,
-			},
-			&EvalInterpolate{
-				Config:   p.ConnInfo.Copy(),
-				Resource: resource,
-				Output:   &connConfig,
-			},
-			&EvalValidateProvisioner{
-				Provisioner: &provisioner,
-				Config:      &config,
-				ConnConfig:  &connConfig,
-			},
-		)
+	if managed := n.Config.Managed; managed != nil {
+		// Validate all the provisioners
+		for _, p := range managed.Provisioners {
+			var provisioner ResourceProvisioner
+			var provisionerSchema *configschema.Block
+			seq.Nodes = append(
+				seq.Nodes,
+				&EvalGetProvisioner{
+					Name:   p.Type,
+					Output: &provisioner,
+					Schema: &provisionerSchema,
+				},
+				&EvalValidateProvisioner{
+					ResourceAddr: addr.Resource,
+					Provisioner:  &provisioner,
+					Schema:       &provisionerSchema,
+					Config:       p,
+				},
+			)
+		}
 	}
 
 	return seq

terraform/node_root_variable.go

@@ -1,22 +1,31 @@
 package terraform
 
 import (
-	"fmt"
-
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
 )
 
 // NodeRootVariable represents a root variable input.
 type NodeRootVariable struct {
-	Config *config.Variable
+	Addr   addrs.InputVariable
+	Config *configs.Variable
 }
 
+var (
+	_ GraphNodeSubPath       = (*NodeRootVariable)(nil)
+	_ GraphNodeReferenceable = (*NodeRootVariable)(nil)
+)
+
 func (n *NodeRootVariable) Name() string {
-	result := fmt.Sprintf("var.%s", n.Config.Name)
-	return result
+	return n.Addr.String()
+}
+
+// GraphNodeSubPath
+func (n *NodeRootVariable) Path() addrs.ModuleInstance {
+	return addrs.RootModuleInstance
 }
 
 // GraphNodeReferenceable
-func (n *NodeRootVariable) ReferenceableName() []string {
-	return []string{n.Name()}
+func (n *NodeRootVariable) ReferenceableAddrs() []addrs.Referenceable {
+	return []addrs.Referenceable{n.Addr}
 }

terraform/path.go

@@ -1,10 +1,17 @@
 package terraform
 
 import (
-	"strings"
+	"fmt"
+
+	"github.com/hashicorp/terraform/addrs"
 )
 
-// PathCacheKey returns a cache key for a module path.
-func PathCacheKey(path []string) string {
-	return strings.Join(path, "|")
+// PathObjectCacheKey is like PathCacheKey but includes an additional name
+// to be included in the key, for module-namespaced objects.
+//
+// The result of this function is guaranteed unique for any distinct pair
+// of path and name, but is not guaranteed to be in any particular format
+// and in particular should never be shown to end-users.
+func PathObjectCacheKey(path addrs.ModuleInstance, objectName string) string {
+	return fmt.Sprintf("%s|%s", path.String(), objectName)
 }

terraform/plan.go

@@ -9,7 +9,13 @@ import (
 	"log"
 	"sync"
 
-	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/hcl2/hcl/hclsyntax"
+	"github.com/zclconf/go-cty/cty"
+
+	"github.com/hashicorp/terraform/addrs"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/tfdiags"
 	"github.com/hashicorp/terraform/version"
 )
 
@@ -31,9 +37,9 @@ type Plan struct {
 	// plan is applied.
 	Diff *Diff
 
-	// Module represents the entire configuration that was present when this
+	// Config represents the entire configuration that was present when this
 	// plan was created.
-	Module *module.Tree
+	Config *configs.Config
 
 	// State is the Terraform state that was current when this plan was
 	// created.
@@ -44,7 +50,7 @@ type Plan struct {
 
 	// Vars retains the variables that were set when creating the plan, so
 	// that the same variables can be applied during apply.
-	Vars map[string]interface{}
+	Vars map[string]cty.Value
 
 	// Targets, if non-empty, contains a set of resource address strings that
 	// identify graph nodes that were selected as targets for plan.
@@ -86,11 +92,13 @@ type Plan struct {
 // If State is not provided, it is set from the plan. If it _is_ provided,
 // it must be Equal to the state stored in plan, but may have a newer
 // serial.
-func (p *Plan) Context(opts *ContextOpts) (*Context, error) {
+func (p *Plan) Context(opts *ContextOpts) (*Context, tfdiags.Diagnostics) {
 	var err error
 	opts, err = p.contextOpts(opts)
 	if err != nil {
-		return nil, err
+		var diags tfdiags.Diagnostics
+		diags = diags.Append(err)
+		return nil, diags
 	}
 	return NewContext(opts)
 }
@@ -101,11 +109,30 @@ func (p *Plan) contextOpts(base *ContextOpts) (*ContextOpts, error) {
 	opts := base
 
 	opts.Diff = p.Diff
-	opts.Module = p.Module
-	opts.Targets = p.Targets
+	opts.Config = p.Config
 	opts.ProviderSHA256s = p.ProviderSHA256s
 	opts.Destroy = p.Destroy
 
+	if len(p.Targets) != 0 {
+		// We're still using target strings in the Plan struct, so we need to
+		// convert to our address representation here.
+		// FIXME: Change the Plan struct to use addrs.Targetable itself, and
+		// then handle these conversions when we read/write plans on disk.
+		targets := make([]addrs.Targetable, len(p.Targets))
+		for i, targetStr := range p.Targets {
+			traversal, travDiags := hclsyntax.ParseTraversalAbs([]byte(targetStr), "", hcl.Pos{})
+			if travDiags.HasErrors() {
+				return nil, travDiags
+			}
+			target, targDiags := addrs.ParseTarget(traversal)
+			if targDiags.HasErrors() {
+				return nil, targDiags.Err()
+			}
+			targets[i] = target.Subject
+		}
+		opts.Targets = targets
+	}
+
 	if opts.State == nil {
 		opts.State = p.State
 	} else if !opts.State.Equal(p.State) {
@@ -128,9 +155,12 @@ func (p *Plan) contextOpts(base *ContextOpts) (*ContextOpts, error) {
 		)
 	}
 
-	opts.Variables = make(map[string]interface{})
+	opts.Variables = make(InputValues)
 	for k, v := range p.Vars {
-		opts.Variables[k] = v
+		opts.Variables[k] = &InputValue{
+			Value:      v,
+			SourceType: ValueFromPlan,
+		}
 	}
 
 	return opts, nil
@@ -158,7 +188,7 @@ func (p *Plan) init() {
 		}
 
 		if p.Vars == nil {
-			p.Vars = make(map[string]interface{})
+			p.Vars = make(map[string]cty.Value)
 		}
 	})
 }

terraform/resource.go

@@ -7,9 +7,15 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/hashicorp/terraform/addrs"
+
+	"github.com/hashicorp/terraform/config/configschema"
+	"github.com/hashicorp/terraform/config/hcl2shim"
+
 	"github.com/hashicorp/terraform/config"
 	"github.com/mitchellh/copystructure"
 	"github.com/mitchellh/reflectwalk"
+	"github.com/zclconf/go-cty/cty"
 )
 
 // ResourceProvisionerConfig is used to pair a provisioner
@@ -25,9 +31,10 @@ type ResourceProvisionerConfig struct {
 	ConnInfo    *config.RawConfig
 }
 
-// Resource encapsulates a resource, its configuration, its provider,
-// its current state, and potentially a desired diff from the state it
-// wants to reach.
+// Resource is a legacy way to identify a particular resource instance.
+//
+// New code should use addrs.ResourceInstance instead. This is still here
+// only for codepaths that haven't been updated yet.
 type Resource struct {
 	// These are all used by the new EvalNode stuff.
 	Name       string
@@ -47,6 +54,31 @@ type Resource struct {
 	Flags        ResourceFlag
 }
 
+// NewResource constructs a legacy Resource object from an
+// addrs.ResourceInstance value.
+//
+// This is provided to shim to old codepaths that haven't been updated away
+// from this type yet. Since this old type is not able to represent instances
+// that have string keys, this function will panic if given a resource address
+// that has a string key.
+func NewResource(addr addrs.ResourceInstance) *Resource {
+	ret := &Resource{
+		Name: addr.Resource.Name,
+		Type: addr.Resource.Type,
+	}
+
+	if addr.Key != addrs.NoKey {
+		switch tk := addr.Key.(type) {
+		case addrs.IntKey:
+			ret.CountIndex = int(tk)
+		default:
+			panic(fmt.Errorf("resource instance with key %#v is not supported", addr.Key))
+		}
+	}
+
+	return ret
+}
+
 // ResourceKind specifies what kind of instance we're working with, whether
 // its a primary instance, a tainted instance, or an orphan.
 type ResourceFlag byte
@@ -72,6 +104,42 @@ type InstanceInfo struct {
 	uniqueExtra string
 }
 
+// NewInstanceInfo constructs an InstanceInfo from an addrs.AbsResource.
+//
+// In spite of the confusing name, an InstanceInfo actually identifies a
+// particular resource rather than a particular resource instance.
+// InstanceInfo is a legacy type, and uses of it should be gradually replaced
+// by direct use of addrs.AbsResource or addrs.AbsResourceInstance as
+// appropriate.
+//
+// The legacy InstanceInfo type cannot represent module instances with instance
+// keys, so this function will panic if given such a path. Uses of this type
+// should all be removed or replaced before implementing "count" and "for_each"
+// arguments on modules in order to avoid such panics.
+func NewInstanceInfo(addr addrs.AbsResource) *InstanceInfo {
+	// We need an old-style []string module path for InstanceInfo.
+	path := make([]string, len(addr.Module))
+	for i, step := range addr.Module {
+		if step.InstanceKey != addrs.NoKey {
+			panic("NewInstanceInfo cannot convert module instance with key")
+		}
+		path[i] = step.Name
+	}
+
+	// This is a funny old meaning of "id" that is no longer current. It should
+	// not be used for anything users might see. Note that it does not include
+	// a representation of the resource mode, and so it's impossible to
+	// determine from an InstanceInfo alone whether it is a managed or data
+	// resource that is being referred to.
+	id := fmt.Sprintf("%s.%s", addr.Resource.Type, addr.Resource.Name)
+
+	return &InstanceInfo{
+		Id:         id,
+		ModulePath: path,
+		Type:       addr.Resource.Type,
+	}
+}
+
 // HumanId is a unique Id that is human-friendly and useful for UI elements.
 func (i *InstanceInfo) HumanId() string {
 	if i == nil {
@@ -137,9 +205,9 @@ func (i *InstanceInfo) uniqueId() string {
 	return prefix
 }
 
-// ResourceConfig holds the configuration given for a resource. This is
-// done instead of a raw `map[string]interface{}` type so that rich
-// methods can be added to it to make dealing with it easier.
+// ResourceConfig is a legacy type that was formerly used to represent
+// interpolatable configuration blocks. It is now only used to shim to old
+// APIs that still use this type, via NewResourceConfigShimmed.
 type ResourceConfig struct {
 	ComputedKeys []string
 	Raw          map[string]interface{}
@@ -155,6 +223,98 @@ func NewResourceConfig(c *config.RawConfig) *ResourceConfig {
 	return result
 }
 
+// NewResourceConfigShimmed wraps a cty.Value of object type in a legacy
+// ResourceConfig object, so that it can be passed to older APIs that expect
+// this wrapping.
+//
+// The returned ResourceConfig is already interpolated and cannot be
+// re-interpolated. It is, therefore, useful only to functions that expect
+// an already-populated ResourceConfig which they then treat as read-only.
+//
+// If the given value is not of an object type that conforms to the given
+// schema then this function will panic.
+func NewResourceConfigShimmed(val cty.Value, schema *configschema.Block) *ResourceConfig {
+	if !val.Type().IsObjectType() {
+		panic(fmt.Errorf("NewResourceConfigShimmed given %#v; an object type is required", val.Type()))
+	}
+	ret := &ResourceConfig{}
+	legacyVal := hcl2shim.ConfigValueFromHCL2(val)
+	ret.Config = legacyVal.(map[string]interface{}) // guaranteed compatible because we require an object type
+	ret.Raw = ret.Config
+
+	// Now we need to walk through our structure and find any unknown values,
+	// producing the separate list ComputedKeys to represent these. We use the
+	// schema here so that we can preserve the expected invariant
+	// that an attribute is always either wholly known or wholly unknown, while
+	// a child block can be partially unknown.
+	ret.ComputedKeys = newResourceConfigShimmedComputedKeys(val, schema, "")
+
+	return ret
+}
+
+// newResourceConfigShimmedComputedKeys finds all of the unknown values in the
+// given object, which must conform to the given schema, returning them in
+// the format that's expected for ResourceConfig.ComputedKeys.
+func newResourceConfigShimmedComputedKeys(obj cty.Value, schema *configschema.Block, prefix string) []string {
+	var ret []string
+	ty := obj.Type()
+
+	for attrName := range schema.Attributes {
+		if !ty.HasAttribute(attrName) {
+			// Should never happen, but we'll tolerate it anyway
+			continue
+		}
+
+		attrVal := obj.GetAttr(attrName)
+		if !attrVal.IsWhollyKnown() {
+			ret = append(ret, prefix+attrName)
+		}
+	}
+
+	for typeName, blockS := range schema.BlockTypes {
+		if !ty.HasAttribute(typeName) {
+			// Should never happen, but we'll tolerate it anyway
+			continue
+		}
+
+		blockVal := obj.GetAttr(typeName)
+		switch blockS.Nesting {
+		case configschema.NestingSingle:
+			keys := newResourceConfigShimmedComputedKeys(blockVal, &blockS.Block, fmt.Sprintf("%s%s.", prefix, typeName))
+			ret = append(ret, keys...)
+		case configschema.NestingList, configschema.NestingSet:
+			// Producing computed keys items for sets is not really useful
+			// since they are not usefully addressable anyway, but we'll treat
+			// them like lists just so that ret.ComputedKeys accounts for them
+			// all. Our legacy system didn't support sets here anyway, so
+			// treating them as lists is the most accurate translation. Although
+			// set traversal isn't in any particular order, it is _stable_ as
+			// long as the list isn't mutated, and so we know we'll see the
+			// same order here as hcl2shim.ConfigValueFromHCL2 would've seen
+			// inside NewResourceConfigShimmed above.
+			i := 0
+			for it := blockVal.ElementIterator(); it.Next(); i++ {
+				_, subVal := it.Element()
+				subPrefix := fmt.Sprintf("%s%d.", prefix, i)
+				keys := newResourceConfigShimmedComputedKeys(subVal, &blockS.Block, subPrefix)
+				ret = append(ret, keys...)
+			}
+		case configschema.NestingMap:
+			for it := blockVal.ElementIterator(); it.Next(); {
+				subK, subVal := it.Element()
+				subPrefix := fmt.Sprintf("%s%s.", prefix, subK.AsString())
+				keys := newResourceConfigShimmedComputedKeys(subVal, &blockS.Block, subPrefix)
+				ret = append(ret, keys...)
+			}
+		default:
+			// Should never happen, since the above is exhaustive.
+			panic(fmt.Errorf("unsupported block nesting type %s", blockS.Nesting))
+		}
+	}
+
+	return ret
+}
+
 // DeepCopy performs a deep copy of the configuration. This makes it safe
 // to modify any of the structures that are part of the resource config without
 // affecting the original configuration.
@@ -374,6 +534,14 @@ func (c *ResourceConfig) get(
 // refactor is complete.
 func (c *ResourceConfig) interpolateForce() {
 	if c.raw == nil {
+		// If we don't have a lowercase "raw" but we _do_ have the uppercase
+		// Raw populated then this indicates that we're recieving a shim
+		// ResourceConfig created by NewResourceConfigShimmed, which is already
+		// fully evaluated and thus this function doesn't need to do anything.
+		if c.Raw != nil {
+			return
+		}
+
 		var err error
 		c.raw, err = config.NewRawConfig(make(map[string]interface{}))
 		if err != nil {

terraform/resource_address.go

@@ -289,6 +289,144 @@ func ParseResourceAddressForInstanceDiff(path []string, key string) (*ResourceAd
 	return addr, nil
 }
 
+// NewLegacyResourceAddress creates a ResourceAddress from a new-style
+// addrs.AbsResource value.
+//
+// This is provided for shimming purposes so that we can still easily call into
+// older functions that expect the ResourceAddress type.
+func NewLegacyResourceAddress(addr addrs.AbsResource) *ResourceAddress {
+	ret := &ResourceAddress{
+		Type: addr.Resource.Type,
+		Name: addr.Resource.Name,
+	}
+
+	switch addr.Resource.Mode {
+	case addrs.ManagedResourceMode:
+		ret.Mode = config.ManagedResourceMode
+	case addrs.DataResourceMode:
+		ret.Mode = config.DataResourceMode
+	default:
+		panic(fmt.Errorf("cannot shim %s to legacy config.ResourceMode value", addr.Resource.Mode))
+	}
+
+	path := make([]string, len(addr.Module))
+	for i, step := range addr.Module {
+		if step.InstanceKey != addrs.NoKey {
+			// At the time of writing this can't happen because we don't
+			// ket generate keyed module instances. This legacy codepath must
+			// be removed before we can support "count" and "for_each" for
+			// modules.
+			panic(fmt.Errorf("cannot shim module instance step with key %#v to legacy ResourceAddress.Path", step.InstanceKey))
+		}
+
+		path[i] = step.Name
+	}
+	ret.Path = path
+	ret.Index = -1
+
+	return ret
+}
+
+// NewLegacyResourceInstanceAddress creates a ResourceAddress from a new-style
+// addrs.AbsResource value.
+//
+// This is provided for shimming purposes so that we can still easily call into
+// older functions that expect the ResourceAddress type.
+func NewLegacyResourceInstanceAddress(addr addrs.AbsResourceInstance) *ResourceAddress {
+	ret := &ResourceAddress{
+		Type: addr.Resource.Resource.Type,
+		Name: addr.Resource.Resource.Name,
+	}
+
+	switch addr.Resource.Resource.Mode {
+	case addrs.ManagedResourceMode:
+		ret.Mode = config.ManagedResourceMode
+	case addrs.DataResourceMode:
+		ret.Mode = config.DataResourceMode
+	default:
+		panic(fmt.Errorf("cannot shim %s to legacy config.ResourceMode value", addr.Resource.Resource.Mode))
+	}
+
+	path := make([]string, len(addr.Module))
+	for i, step := range addr.Module {
+		if step.InstanceKey != addrs.NoKey {
+			// At the time of writing this can't happen because we don't
+			// ket generate keyed module instances. This legacy codepath must
+			// be removed before we can support "count" and "for_each" for
+			// modules.
+			panic(fmt.Errorf("cannot shim module instance step with key %#v to legacy ResourceAddress.Path", step.InstanceKey))
+		}
+
+		path[i] = step.Name
+	}
+	ret.Path = path
+
+	if addr.Resource.Key == addrs.NoKey {
+		ret.Index = 0
+	} else if ik, ok := addr.Resource.Key.(addrs.IntKey); ok {
+		ret.Index = int(ik)
+	} else {
+		panic(fmt.Errorf("cannot shim resource instance with key %#v to legacy ResourceAddress.Index", addr.Resource.Key))
+	}
+
+	return ret
+}
+
+// AbsResourceInstanceAddr converts the receiver, a legacy resource address, to
+// the new resource address type addrs.AbsResourceInstance.
+//
+// This method can be used only on an address that has a resource specification.
+// It will panic if called on a module-path-only ResourceAddress. Use
+// method HasResourceSpec to check before calling, in contexts where it is
+// unclear.
+//
+// addrs.AbsResourceInstance does not represent the "tainted" and "deposed"
+// states, and so if these are present on the receiver then they are discarded.
+//
+// This is provided for shimming purposes so that we can easily adapt functions
+// that are returning the legacy ResourceAddress type, for situations where
+// the new type is required.
+func (addr *ResourceAddress) AbsResourceInstanceAddr() addrs.AbsResourceInstance {
+	if !addr.HasResourceSpec() {
+		panic("AbsResourceInstanceAddr called on ResourceAddress with no resource spec")
+	}
+
+	ret := addrs.AbsResourceInstance{
+		Module: addr.ModuleInstanceAddr(),
+		Resource: addrs.ResourceInstance{
+			Resource: addrs.Resource{
+				Type: addr.Type,
+				Name: addr.Name,
+			},
+		},
+	}
+
+	switch addr.Mode {
+	case config.ManagedResourceMode:
+		ret.Resource.Resource.Mode = addrs.ManagedResourceMode
+	case config.DataResourceMode:
+		ret.Resource.Resource.Mode = addrs.DataResourceMode
+	default:
+		panic(fmt.Errorf("cannot shim %s to addrs.ResourceMode value", addr.Mode))
+	}
+
+	if addr.Index != -1 {
+		ret.Resource.Key = addrs.IntKey(addr.Index)
+	}
+
+	return ret
+}
+
+// ModuleInstanceAddr returns the module path portion of the receiver as a
+// addrs.ModuleInstance value.
+func (addr *ResourceAddress) ModuleInstanceAddr() addrs.ModuleInstance {
+	path := make(addrs.ModuleInstance, len(addr.Path))
+	for i, name := range addr.Path {
+		path[i] = addrs.ModuleInstanceStep{Name: name}
+	}
+	return path
+}
+
 // Contains returns true if and only if the given node is contained within
 // the receiver.
 //

terraform/resource_provisioner.go

@@ -1,9 +1,20 @@
 package terraform
 
+import (
+	"github.com/hashicorp/terraform/config/configschema"
+)
+
 // ResourceProvisioner is an interface that must be implemented by any
 // resource provisioner: the thing that initializes resources in
 // a Terraform configuration.
 type ResourceProvisioner interface {
+	// GetConfigSchema returns the schema for the provisioner type's main
+	// configuration block. This is called prior to Validate to enable some
+	// basic structural validation to be performed automatically and to allow
+	// the configuration to be properly extracted from potentially-ambiguous
+	// configuration file formats.
+	GetConfigSchema() (*configschema.Block, error)
+
 	// Validate is called once at the beginning with the raw
 	// configuration (no interpolation done) and can return a list of warnings
 	// and/or errors.

terraform/semantics.go

@@ -2,11 +2,13 @@ package terraform
 
 import (
 	"fmt"
-	"strings"
 
 	"github.com/hashicorp/go-multierror"
-	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/dag"
+	"github.com/hashicorp/terraform/tfdiags"
+	"github.com/zclconf/go-cty/cty/convert"
 )
 
 // GraphSemanticChecker is the interface that semantic checks across
@@ -49,84 +51,87 @@ type SemanticChecker interface {
 	Check(*dag.Graph, dag.Vertex) error
 }
 
-// smcUserVariables does all the semantic checks to verify that the
-// variables given satisfy the configuration itself.
-func smcUserVariables(c *config.Config, vs map[string]interface{}) []error {
-	var errs []error
+// checkInputVariables ensures that variable values supplied at the UI conform
+// to their corresponding declarations in configuration.
+//
+// The set of values is considered valid only if the returned diagnostics
+// does not contain errors. A valid set of values may still produce warnings,
+// which should be returned to the user.
+func checkInputVariables(vcs map[string]*configs.Variable, vs InputValues) tfdiags.Diagnostics {
+	var diags tfdiags.Diagnostics
 
-	cvs := make(map[string]*config.Variable)
-	for _, v := range c.Variables {
-		cvs[v.Name] = v
-	}
-
-	// Check that all required variables are present
-	required := make(map[string]struct{})
-	for _, v := range c.Variables {
-		if v.Required() {
-			required[v.Name] = struct{}{}
-		}
-	}
-	for k, _ := range vs {
-		delete(required, k)
-	}
-	if len(required) > 0 {
-		for k, _ := range required {
-			errs = append(errs, fmt.Errorf(
-				"Required variable not set: %s", k))
-		}
-	}
-
-	// Check that types match up
-	for name, proposedValue := range vs {
-		// Check for "map.key" fields. These stopped working with Terraform
-		// 0.7 but we do this to surface a better error message informing
-		// the user what happened.
-		if idx := strings.Index(name, "."); idx > 0 {
-			key := name[:idx]
-			if _, ok := cvs[key]; ok {
-				errs = append(errs, fmt.Errorf(
-					"%s: Overriding map keys with the format `name.key` is no "+
-						"longer allowed. You may still override keys by setting "+
-						"`name = { key = value }`. The maps will be merged. This "+
-						"behavior appeared in 0.7.0.", name))
-				continue
-			}
-		}
-
-		schema, ok := cvs[name]
-		if !ok {
+	for name, vc := range vcs {
+		val, isSet := vs[name]
+		if !isSet {
+			// Always an error, since the caller should already have included
+			// default values from the configuration in the values map.
+			diags = diags.Append(tfdiags.Sourceless(
+				tfdiags.Error,
+				"Unassigned variable",
+				fmt.Sprintf("The input variable %q has not been assigned a value. This is a bug in Terraform; please report it in a GitHub issue.", name),
+			))
 			continue
 		}
 
-		declaredType := schema.Type()
+		wantType := vc.Type
 
-		switch declaredType {
-		case config.VariableTypeString:
-			switch proposedValue.(type) {
-			case string:
-				continue
-			}
-		case config.VariableTypeMap:
-			switch v := proposedValue.(type) {
-			case map[string]interface{}:
-				continue
-			case []map[string]interface{}:
-				// if we have a list of 1 map, it will get coerced later as needed
-				if len(v) == 1 {
-					continue
-				}
-			}
-		case config.VariableTypeList:
-			switch proposedValue.(type) {
-			case []interface{}:
-				continue
+		// A given value is valid if it can convert to the desired type.
+		_, err := convert.Convert(val.Value, wantType)
+		if err != nil {
+			switch val.SourceType {
+			case ValueFromConfig, ValueFromFile:
+				// We have source location information for these.
+				diags = diags.Append(&hcl.Diagnostic{
+					Severity: hcl.DiagError,
+					Summary:  "Invalid value for input variable",
+					Detail:   fmt.Sprintf("The given value is not valid for variable %q: %s.", name, err),
+					Subject:  val.SourceRange.ToHCL().Ptr(),
+				})
+			case ValueFromEnvVar:
+				diags = diags.Append(tfdiags.Sourceless(
+					tfdiags.Error,
+					"Invalid value for input variable",
+					fmt.Sprintf("The environment variable TF_VAR_%s does not contain a valid value for variable %q: %s.", name, name, err),
+				))
+			case ValueFromCLIArg:
+				diags = diags.Append(tfdiags.Sourceless(
+					tfdiags.Error,
+					"Invalid value for input variable",
+					fmt.Sprintf("The argument -var=\"%s=...\" does not contain a valid value for variable %q: %s.", name, name, err),
+				))
+			case ValueFromInput:
+				diags = diags.Append(tfdiags.Sourceless(
+					tfdiags.Error,
+					"Invalid value for input variable",
+					fmt.Sprintf("The value entered for variable %q is not valid: %s.", name, err),
+				))
+			default:
+				// The above gets us good coverage for the situations users
+				// are likely to encounter with their own inputs. The other
+				// cases are generally implementation bugs, so we'll just
+				// use a generic error for these.
+				diags = diags.Append(tfdiags.Sourceless(
+					tfdiags.Error,
+					"Invalid value for input variable",
+					fmt.Sprintf("The value provided for variable %q is not valid: %s.", name, err),
+				))
 			}
 		}
-		errs = append(errs, fmt.Errorf("variable %s should be type %s, got %s",
-			name, declaredType.Printable(), hclTypeName(proposedValue)))
 	}
 
-	// TODO(mitchellh): variables that are unknown
+	// Check for any variables that are assigned without being configured.
+	// This is always an implementation error in the caller, because we
+	// expect undefined variables to be caught during context construction
+	// where there is better context to report it well.
+	for name := range vs {
+		if _, defined := vcs[name]; !defined {
+			diags = diags.Append(tfdiags.Sourceless(
+				tfdiags.Error,
+				"Value assigned to undeclared variable",
+				fmt.Sprintf("A value was assigned to an undeclared input variable %q.", name),
+			))
+		}
+	}
 
-	return errs
+	return diags
 }

terraform/semantics_test.go

@@ -2,56 +2,43 @@ package terraform
 
 import (
 	"testing"
+
+	"github.com/zclconf/go-cty/cty"
 )
 
 func TestSMCUserVariables(t *testing.T) {
-	c := testConfig(t, "smc-uservars")
+	c := testModule(t, "smc-uservars")
 
 	// Required variables not set
-	errs := smcUserVariables(c, nil)
-	if len(errs) == 0 {
-		t.Fatal("should have errors")
+	diags := checkInputVariables(c.Module.Variables, nil)
+	if !diags.HasErrors() {
+		t.Fatal("check succeeded, but want errors")
 	}
 
 	// Required variables set, optional variables unset
-	errs = smcUserVariables(c, map[string]interface{}{"foo": "bar"})
-	if len(errs) != 0 {
-		t.Fatalf("err: %#v", errs)
-	}
-
-	// Mapping element override
-	errs = smcUserVariables(c, map[string]interface{}{
-		"foo":     "bar",
-		"map.foo": "baz",
+	diags = checkInputVariables(c.Module.Variables, InputValues{
+		"foo": &InputValue{
+			Value:      cty.StringVal("bar"),
+			SourceType: ValueFromCLIArg,
+		},
 	})
-	if len(errs) == 0 {
-		t.Fatalf("err: %#v", errs)
+	if diags.HasErrors() {
+		t.Fatalf("unexpected errors: %s", diags.Err())
 	}
 
 	// Mapping complete override
-	errs = smcUserVariables(c, map[string]interface{}{
-		"foo": "bar",
-		"map": "baz",
-	})
-	if len(errs) == 0 {
-		t.Fatal("should have errors")
-	}
-
-}
-
-func TestSMCUserVariables_mapFromJSON(t *testing.T) {
-	c := testConfig(t, "uservars-map")
-
-	// ensure that a single map in a list can satisfy a map variable, since it
-	// will be coerced later to a map
-	err := smcUserVariables(c, map[string]interface{}{
-		"test_map": []map[string]interface{}{
-			map[string]interface{}{
-				"foo": "bar",
-			},
+	diags = checkInputVariables(c.Module.Variables, InputValues{
+		"foo": &InputValue{
+			Value:      cty.StringVal("bar"),
+			SourceType: ValueFromCLIArg,
+		},
+		"map": &InputValue{
+			Value:      cty.StringVal("baz"),
+			SourceType: ValueFromCLIArg,
 		},
 	})
-	if err != nil {
-		t.Fatal(err)
+	if !diags.HasErrors() {
+		t.Fatal("check succeeded, but want errors")
 	}
+
 }

terraform/state.go

@@ -19,13 +19,17 @@ import (
 	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/go-uuid"
 	"github.com/hashicorp/go-version"
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/hcl2/hcl/hclsyntax"
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/config"
 	"github.com/hashicorp/terraform/config/configschema"
+	"github.com/hashicorp/terraform/configs"
+	"github.com/hashicorp/terraform/tfdiags"
 	tfversion "github.com/hashicorp/terraform/version"
+	"github.com/mitchellh/copystructure"
 	"github.com/zclconf/go-cty/cty"
 	ctyjson "github.com/zclconf/go-cty/cty/json"
-
-	"github.com/mitchellh/copystructure"
 )
 
 const (
@@ -36,26 +40,38 @@ const (
 // rootModulePath is the path of the root module
 var rootModulePath = []string{"root"}
 
+// normalizeModulePath transforms a legacy module path (which may or may not
+// have a redundant "root" label at the start of it) into an
+// addrs.ModuleInstance representing the same module.
+//
+// For legacy reasons, different parts of Terraform disagree about whether the
+// root module has the path []string{} or []string{"root"}, and so this
+// function accepts both and trims off the "root". An implication of this is
+// that it's not possible to actually have a module call in the root module
+// that is itself named "root", since that would be ambiguous.
+//
 // normalizeModulePath takes a raw module path and returns a path that
 // has the rootModulePath prepended to it. If I could go back in time I
 // would've never had a rootModulePath (empty path would be root). We can
 // still fix this but thats a big refactor that my branch doesn't make sense
 // for. Instead, this function normalizes paths.
-func normalizeModulePath(p []string) []string {
-	k := len(rootModulePath)
+func normalizeModulePath(p []string) addrs.ModuleInstance {
+	// FIXME: Remove this once everyone is using addrs.ModuleInstance.
 
-	// If we already have a root module prefix, we're done
-	if len(p) >= len(rootModulePath) {
-		if reflect.DeepEqual(p[:k], rootModulePath) {
-			return p
-		}
+	if len(p) > 0 && p[0] == "root" {
+		p = p[1:]
 	}
 
-	// None? Prefix it
-	result := make([]string, len(rootModulePath)+len(p))
-	copy(result, rootModulePath)
-	copy(result[k:], p)
-	return result
+	ret := make(addrs.ModuleInstance, len(p))
+	for i, name := range p {
+		// For now we don't actually support modules with multiple instances
+		// identified by keys, so we just treat every path element as a
+		// step with no key.
+		ret[i] = addrs.ModuleInstanceStep{
+			Name: name,
+		}
+	}
+	return ret
 }
 
 // State keeps track of a snapshot state-of-the-world that Terraform
@@ -141,21 +157,37 @@ func (s *State) children(path []string) []*ModuleState {
 //
 // This should be the preferred method to add module states since it
 // allows us to optimize lookups later as well as control sorting.
-func (s *State) AddModule(path []string) *ModuleState {
+func (s *State) AddModule(path addrs.ModuleInstance) *ModuleState {
 	s.Lock()
 	defer s.Unlock()
 
 	return s.addModule(path)
 }
 
-func (s *State) addModule(path []string) *ModuleState {
+func (s *State) addModule(path addrs.ModuleInstance) *ModuleState {
 	// check if the module exists first
 	m := s.moduleByPath(path)
 	if m != nil {
 		return m
 	}
 
-	m = &ModuleState{Path: path}
+	// Lower the new-style address into a legacy-style address.
+	// This requires that none of the steps have instance keys, which is
+	// true for all addresses at the time of implementing this because
+	// "count" and "for_each" are not yet implemented for modules.
+	legacyPath := make([]string, len(path))
+	for i, step := range path {
+		if step.InstanceKey != addrs.NoKey {
+			// FIXME: Once the rest of Terraform is ready to use count and
+			// for_each, remove all of this and just write the addrs.ModuleInstance
+			// value itself into the ModuleState.
+			panic("state cannot represent modules with count or for_each keys")
+		}
+
+		legacyPath[i] = step.Name
+	}
+
+	m = &ModuleState{Path: legacyPath}
 	m.init()
 	s.Modules = append(s.Modules, m)
 	s.sort()
@@ -165,7 +197,7 @@ func (s *State) addModule(path []string) *ModuleState {
 // ModuleByPath is used to lookup the module state for the given path.
 // This should be the preferred lookup mechanism as it allows for future
 // lookup optimizations.
-func (s *State) ModuleByPath(path []string) *ModuleState {
+func (s *State) ModuleByPath(path addrs.ModuleInstance) *ModuleState {
 	if s == nil {
 		return nil
 	}
@@ -175,7 +207,7 @@ func (s *State) ModuleByPath(path []string) *ModuleState {
 	return s.moduleByPath(path)
 }
 
-func (s *State) moduleByPath(path []string) *ModuleState {
+func (s *State) moduleByPath(path addrs.ModuleInstance) *ModuleState {
 	for _, mod := range s.Modules {
 		if mod == nil {
 			continue
@@ -183,7 +215,8 @@ func (s *State) moduleByPath(path []string) *ModuleState {
 		if mod.Path == nil {
 			panic("missing module path")
 		}
-		if reflect.DeepEqual(mod.Path, path) {
+		modPath := normalizeModulePath(mod.Path)
+		if modPath.String() == path.String() {
 			return mod
 		}
 	}
@@ -397,8 +430,9 @@ func (s *State) Remove(addr ...string) error {
 	// Go through each result and grab what we need
 	removed := make(map[interface{}]struct{})
 	for _, r := range results {
-		// Convert the path to our own type
-		path := append([]string{"root"}, r.Path...)
+		// Convert the legacy path used by the state filter API into a
+		// new-style module instance address.
+		path := normalizeModulePath(r.Path)
 
 		// If we removed this already, then ignore
 		if _, ok := removed[r.Value]; ok {
@@ -435,7 +469,7 @@ func (s *State) Remove(addr ...string) error {
 	return nil
 }
 
-func (s *State) removeModule(path []string, v *ModuleState) {
+func (s *State) removeModule(path addrs.ModuleInstance, v *ModuleState) {
 	for i, m := range s.Modules {
 		if m == v {
 			s.Modules, s.Modules[len(s.Modules)-1] = append(s.Modules[:i], s.Modules[i+1:]...), nil
@@ -444,7 +478,7 @@ func (s *State) removeModule(path []string, v *ModuleState) {
 	}
 }
 
-func (s *State) removeResource(path []string, v *ResourceState) {
+func (s *State) removeResource(path addrs.ModuleInstance, v *ResourceState) {
 	// Get the module this resource lives in. If it doesn't exist, we're done.
 	mod := s.moduleByPath(path)
 	if mod == nil {
@@ -463,7 +497,7 @@ func (s *State) removeResource(path []string, v *ResourceState) {
 	}
 }
 
-func (s *State) removeInstance(path []string, r *ResourceState, v *InstanceState) {
+func (s *State) removeInstance(path addrs.ModuleInstance, r *ResourceState, v *InstanceState) {
 	// Go through the resource and find the instance that matches this
 	// (if any) and remove it.
 
@@ -490,7 +524,7 @@ func (s *State) removeInstance(path []string, r *ResourceState, v *InstanceState
 
 // RootModule returns the ModuleState for the root module
 func (s *State) RootModule() *ModuleState {
-	root := s.ModuleByPath(rootModulePath)
+	root := s.ModuleByPath(addrs.RootModuleInstance)
 	if root == nil {
 		panic("missing root module")
 	}
@@ -525,7 +559,7 @@ func (s *State) equal(other *State) bool {
 	}
 	for _, m := range s.Modules {
 		// This isn't very optimal currently but works.
-		otherM := other.moduleByPath(m.Path)
+		otherM := other.moduleByPath(normalizeModulePath(m.Path))
 		if otherM == nil {
 			return false
 		}
@@ -684,8 +718,8 @@ func (s *State) init() {
 		s.Version = StateVersion
 	}
 
-	if s.moduleByPath(rootModulePath) == nil {
-		s.addModule(rootModulePath)
+	if s.moduleByPath(addrs.RootModuleInstance) == nil {
+		s.addModule(addrs.RootModuleInstance)
 	}
 	s.ensureHasLineage()
 
@@ -1092,58 +1126,60 @@ func (m *ModuleState) IsDescendent(other *ModuleState) bool {
 // Orphans returns a list of keys of resources that are in the State
 // but aren't present in the configuration itself. Hence, these keys
 // represent the state of resources that are orphans.
-func (m *ModuleState) Orphans(c *config.Config) []string {
+func (m *ModuleState) Orphans(c *configs.Module) []addrs.ResourceInstance {
 	m.Lock()
 	defer m.Unlock()
 
-	keys := make(map[string]struct{})
-	for k := range m.Resources {
-		keys[k] = struct{}{}
-	}
-
+	inConfig := make(map[string]struct{})
 	if c != nil {
-		for _, r := range c.Resources {
-			delete(keys, r.Id())
-
-			for k := range keys {
-				if strings.HasPrefix(k, r.Id()+".") {
-					delete(keys, k)
-				}
-			}
+		for _, r := range c.ManagedResources {
+			inConfig[r.Addr().String()] = struct{}{}
+		}
+		for _, r := range c.DataResources {
+			inConfig[r.Addr().String()] = struct{}{}
 		}
 	}
 
-	result := make([]string, 0, len(keys))
-	for k := range keys {
-		result = append(result, k)
-	}
+	var result []addrs.ResourceInstance
+	for k := range m.Resources {
+		// Since we've not yet updated state to use our new address format,
+		// we need to do some shimming here.
+		legacyAddr, err := parseResourceAddressInternal(k)
+		if err != nil {
+			// Suggests that the user tampered with the state, since we always
+			// generate valid internal addresses.
+			log.Printf("ModuleState has invalid resource key %q. Ignoring.", k)
+			continue
+		}
 
+		addr := legacyAddr.AbsResourceInstanceAddr().Resource
+		compareKey := addr.Resource.String() // compare by resource address, ignoring instance key
+		if _, exists := inConfig[compareKey]; !exists {
+			result = append(result, addr)
+		}
+	}
 	return result
 }
 
 // RemovedOutputs returns a list of outputs that are in the State but aren't
 // present in the configuration itself.
-func (m *ModuleState) RemovedOutputs(c *config.Config) []string {
-	m.Lock()
-	defer m.Unlock()
-
-	keys := make(map[string]struct{})
-	for k := range m.Outputs {
-		keys[k] = struct{}{}
+func (s *ModuleState) RemovedOutputs(outputs map[string]*configs.Output) []addrs.OutputValue {
+	if len(outputs) == 0 {
+		return nil
 	}
+	s.Lock()
+	defer s.Unlock()
 
-	if c != nil {
-		for _, o := range c.Outputs {
-			delete(keys, o.Name)
+	var ret []addrs.OutputValue
+	for n := range s.Outputs {
+		if _, declared := outputs[n]; !declared {
+			ret = append(ret, addrs.OutputValue{
+				Name: n,
+			})
 		}
 	}
 
-	result := make([]string, 0, len(keys))
-	for k := range keys {
-		result = append(result, k)
-	}
-
-	return result
+	return ret
 }
 
 // View returns a view with the given resource prefix.
@@ -1546,6 +1582,24 @@ func (s *ResourceState) Untaint() {
 	}
 }
 
+// ProviderAddr returns the provider address for the receiver, by parsing the
+// string representation saved in state. An error can be returned if the
+// value in state is corrupt.
+func (s *ResourceState) ProviderAddr() (addrs.AbsProviderConfig, error) {
+	var diags tfdiags.Diagnostics
+
+	str := s.Provider
+	traversal, travDiags := hclsyntax.ParseTraversalAbs([]byte(str), "", hcl.Pos{Line: 1, Column: 1})
+	diags = diags.Append(travDiags)
+	if travDiags.HasErrors() {
+		return addrs.AbsProviderConfig{}, diags.Err()
+	}
+
+	addr, addrDiags := addrs.ParseAbsProviderConfig(traversal)
+	diags = diags.Append(addrDiags)
+	return addr, diags.Err()
+}
+
 func (s *ResourceState) init() {
 	s.Lock()
 	defer s.Unlock()
@@ -2190,17 +2244,27 @@ func (s moduleStateSort) Swap(i, j int) {
 	s[i], s[j] = s[j], s[i]
 }
 
-// StateCompatible returns an error if the state is not compatible with the
-// current version of terraform.
-func CheckStateVersion(state *State) error {
+// CheckStateVersion returns error diagnostics if the state is not compatible
+// with the current version of Terraform Core.
+func CheckStateVersion(state *State, allowFuture bool) tfdiags.Diagnostics {
+	var diags tfdiags.Diagnostics
+
 	if state == nil {
-		return nil
+		return diags
 	}
 
-	if state.FromFutureTerraform() {
-		return fmt.Errorf(stateInvalidTerraformVersionErr, state.TFVersion)
+	if state.FromFutureTerraform() && !allowFuture {
+		diags = diags.Append(tfdiags.Sourceless(
+			tfdiags.Error,
+			"Incompatible Terraform state format",
+			fmt.Sprintf(
+				"For safety reasons, Terraform will not run operations against a state that was written by a future Terraform version. Your current version is %s, but the state requires at least %s. To proceed, upgrade Terraform to a suitable version.",
+				tfversion.String(), state.TFVersion,
+			),
+		))
 	}
-	return nil
+
+	return diags
 }
 
 const stateValidateErrMultiModule = `
@@ -2211,11 +2275,3 @@ in your state file that point to the same module. This will cause Terraform
 to behave in unexpected and error prone ways and is invalid. Please back up
 and modify your state file manually to resolve this.
 `
-
-const stateInvalidTerraformVersionErr = `
-Terraform doesn't allow running any operations against a state
-that was written by a future Terraform version. The state is
-reporting it is written by Terraform '%s'
-
-Please run at least that version of Terraform to continue.
-`

terraform/state_add.go

@@ -91,7 +91,7 @@ func stateAddFunc_Module_Module(s *State, fromAddr, addr *ResourceAddress, raw i
 	src := root.(*ModuleState).deepcopy()
 
 	// If the target module exists, it is an error
-	path := append([]string{"root"}, addr.Path...)
+	path := normalizeModulePath(addr.Path)
 	if s.ModuleByPath(path) != nil {
 		return fmt.Errorf("module target is not empty: %s", addr)
 	}
@@ -317,7 +317,7 @@ func stateAddInitAddr(s *State, addr *ResourceAddress) (interface{}, bool) {
 	addType := detectAddrAddLoc(addr)
 
 	// Get the module
-	path := append([]string{"root"}, addr.Path...)
+	path := normalizeModulePath(addr.Path)
 	exists := true
 	mod := s.ModuleByPath(path)
 	if mod == nil {