terraform: don't prune, but disable, inherited configs [GH-1447]

terraform/context_test.go

@@ -2258,6 +2258,29 @@ func TestContext2Validate_moduleProviderVar(t *testing.T) {
 	}
 }
 
+func TestContext2Validate_moduleProviderInheritUnused(t *testing.T) {
+	m := testModule(t, "validate-module-pc-inherit-unused")
+	p := testProvider("aws")
+	c := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	p.ValidateFn = func(c *ResourceConfig) ([]string, []error) {
+		return nil, c.CheckSet([]string{"foo"})
+	}
+
+	w, e := c.Validate()
+	if len(w) > 0 {
+		t.Fatalf("bad: %#v", w)
+	}
+	if len(e) > 0 {
+		t.Fatalf("bad: %s", e)
+	}
+}
+
 func TestContext2Validate_orphans(t *testing.T) {
 	p := testProvider("aws")
 	m := testModule(t, "validate-good")

terraform/eval_context.go

@@ -33,6 +33,7 @@ type EvalContext interface {
 	// is used to store the provider configuration for inheritance lookups
 	// with ParentProviderConfig().
 	ConfigureProvider(string, *ResourceConfig) error
+	SetProviderConfig(string, *ResourceConfig) error
 	ParentProviderConfig(string) *ResourceConfig
 
 	// ProviderInput and SetProviderInput are used to configure providers

terraform/eval_context_builtin.go

@@ -106,6 +106,15 @@ func (ctx *BuiltinEvalContext) ConfigureProvider(
 		return fmt.Errorf("Provider '%s' not initialized", n)
 	}
 
+	if err := ctx.SetProviderConfig(n, cfg); err != nil {
+		return nil
+	}
+
+	return p.Configure(cfg)
+}
+
+func (ctx *BuiltinEvalContext) SetProviderConfig(
+	n string, cfg *ResourceConfig) error {
 	providerPath := make([]string, len(ctx.Path())+1)
 	copy(providerPath, ctx.Path())
 	providerPath[len(providerPath)-1] = n
@@ -115,7 +124,7 @@ func (ctx *BuiltinEvalContext) ConfigureProvider(
 	ctx.ProviderConfigCache[PathCacheKey(providerPath)] = cfg
 	ctx.ProviderLock.Unlock()
 
-	return p.Configure(cfg)
+	return nil
 }
 
 func (ctx *BuiltinEvalContext) ProviderInput(n string) map[string]interface{} {

terraform/eval_context_mock.go

@@ -38,6 +38,10 @@ type MockEvalContext struct {
 	ConfigureProviderConfig *ResourceConfig
 	ConfigureProviderError  error
 
+	SetProviderConfigCalled bool
+	SetProviderConfigName   string
+	SetProviderConfigConfig *ResourceConfig
+
 	ParentProviderConfigCalled bool
 	ParentProviderConfigName   string
 	ParentProviderConfigConfig *ResourceConfig
@@ -107,6 +111,14 @@ func (c *MockEvalContext) ConfigureProvider(n string, cfg *ResourceConfig) error
 	return c.ConfigureProviderError
 }
 
+func (c *MockEvalContext) SetProviderConfig(
+	n string, cfg *ResourceConfig) error {
+	c.SetProviderConfigCalled = true
+	c.SetProviderConfigName = n
+	c.SetProviderConfigConfig = cfg
+	return nil
+}
+
 func (c *MockEvalContext) ParentProviderConfig(n string) *ResourceConfig {
 	c.ParentProviderConfigCalled = true
 	c.ParentProviderConfigName = n

terraform/eval_provider.go

@@ -6,6 +6,17 @@ import (
 	"github.com/hashicorp/terraform/config"
 )
 
+// EvalSetProviderConfig sets the parent configuration for a provider
+// without configuring that provider, validating it, etc.
+type EvalSetProviderConfig struct {
+	Provider string
+	Config   **ResourceConfig
+}
+
+func (n *EvalSetProviderConfig) Eval(ctx EvalContext) (interface{}, error) {
+	return nil, ctx.SetProviderConfig(n.Provider, *n.Config)
+}
+
 // EvalBuildProviderConfig outputs a *ResourceConfig that is properly
 // merged with parents and inputs on top of what is configured in the file.
 type EvalBuildProviderConfig struct {

terraform/graph_config_node.go

@@ -209,6 +209,11 @@ func (n *GraphNodeConfigProvider) ProviderName() string {
 	return n.Provider.Name
 }
 
+// GraphNodeProvider implementation
+func (n *GraphNodeConfigProvider) ProviderConfig() *config.RawConfig {
+	return n.Provider.RawConfig
+}
+
 // GraphNodeDotter impl.
 func (n *GraphNodeConfigProvider) Dot(name string) string {
 	return fmt.Sprintf(

terraform/test-fixtures/validate-module-pc-inherit-unused/child/main.tf

@@ -0,0 +1 @@
+resource "aws_instance" "foo" {}

terraform/test-fixtures/validate-module-pc-inherit-unused/main.tf

@@ -0,0 +1,7 @@
+module "child" {
+    source = "./child"
+}
+
+provider "aws" {
+    foo = "set"
+}

terraform/transform_provider.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/hashicorp/go-multierror"
+	"github.com/hashicorp/terraform/config"
 	"github.com/hashicorp/terraform/dag"
 )
 
@@ -12,6 +13,7 @@ import (
 // they satisfy.
 type GraphNodeProvider interface {
 	ProviderName() string
+	ProviderConfig() *config.RawConfig
 }
 
 // GraphNodeProviderConsumer is an interface that nodes that require
@@ -28,7 +30,8 @@ type DisableProviderTransformer struct{}
 func (t *DisableProviderTransformer) Transform(g *Graph) error {
 	for _, v := range g.Vertices() {
 		// We only care about providers
-		if _, ok := v.(GraphNodeProvider); !ok {
+		pn, ok := v.(GraphNodeProvider)
+		if !ok {
 			continue
 		}
 
@@ -54,8 +57,13 @@ func (t *DisableProviderTransformer) Transform(g *Graph) error {
 			continue
 		}
 
-		// Disable the provider by removing it from the graph.
-		g.Remove(v)
+		// Disable the provider by replacing it with a "disabled" provider
+		disabled := &graphNodeDisabledProvider{GraphNodeProvider: pn}
+		if !g.Replace(v, disabled) {
+			panic(fmt.Sprintf(
+				"vertex disappeared from under us: %s",
+				dag.VertexName(v)))
+		}
 	}
 
 	return nil
@@ -134,6 +142,36 @@ func (t *PruneProviderTransformer) Transform(g *Graph) error {
 	return nil
 }
 
+type graphNodeDisabledProvider struct {
+	GraphNodeProvider
+}
+
+// GraphNodeEvalable impl.
+func (n *graphNodeDisabledProvider) EvalTree() EvalNode {
+	var resourceConfig *ResourceConfig
+
+	return &EvalOpFilter{
+		Ops: []walkOperation{walkValidate, walkRefresh, walkPlan, walkApply},
+		Node: &EvalSequence{
+			Nodes: []EvalNode{
+				&EvalInterpolate{
+					Config: n.ProviderConfig(),
+					Output: &resourceConfig,
+				},
+				&EvalBuildProviderConfig{
+					Provider: n.ProviderName(),
+					Config:   &resourceConfig,
+					Output:   &resourceConfig,
+				},
+				&EvalSetProviderConfig{
+					Provider: n.ProviderName(),
+					Config:   &resourceConfig,
+				},
+			},
+		},
+	}
+}
+
 type graphNodeMissingProvider struct {
 	ProviderNameValue string
 }
@@ -151,6 +189,10 @@ func (n *graphNodeMissingProvider) ProviderName() string {
 	return n.ProviderNameValue
 }
 
+func (n *graphNodeMissingProvider) ProviderConfig() *config.RawConfig {
+	return nil
+}
+
 // GraphNodeDotter impl.
 func (n *graphNodeMissingProvider) Dot(name string) string {
 	return fmt.Sprintf(