terraform: Shadow interface, properly string through errors at the right

time

terraform/context.go

@@ -2,7 +2,6 @@ package terraform
 
 import (
 	"fmt"
-	"io"
 	"log"
 	"sort"
 	"strings"
@@ -615,7 +614,7 @@ func (c *Context) walk(
 	// If we have a shadow graph, walk that as well
 	var shadowCtx *Context
 	var shadowCh chan error
-	var shadowCloser io.Closer
+	var shadowCloser Shadow
 	if shadow != nil {
 		// Build the shadow context. In the process, override the real context
 		// with the one that is wrapped so that the shadow context can verify
@@ -647,13 +646,16 @@ func (c *Context) walk(
 	// If we have a shadow graph, wait for that to complete
 	if shadowCloser != nil {
 		// Notify the shadow that we're done
-		if err := shadowCloser.Close(); err != nil {
+		if err := shadowCloser.CloseShadow(); err != nil {
 			c.shadowErr = multierror.Append(c.shadowErr, err)
 		}
 
 		// Wait for the walk to end
 		log.Printf("[DEBUG] Waiting for shadow graph to complete...")
-		if err := <-shadowCh; err != nil {
+		shadowWalkErr := <-shadowCh
+
+		// Get any shadow errors
+		if err := shadowCloser.ShadowError(); err != nil {
 			c.shadowErr = multierror.Append(c.shadowErr, err)
 		}
 
@@ -662,6 +664,22 @@ func (c *Context) walk(
 			c.shadowErr = multierror.Append(c.shadowErr, err)
 		}
 
+		// At this point, if we're supposed to fail on error, then
+		// we PANIC. Some tests just verify that there is an error,
+		// so simply appending it to realErr and returning could hide
+		// shadow problems.
+		//
+		// This must be done BEFORE appending shadowWalkErr since the
+		// shadowWalkErr may include expected errors.
+		if c.shadowErr != nil && contextFailOnShadowError {
+			panic(multierror.Prefix(c.shadowErr, "shadow graph:"))
+		}
+
+		// Now, if we have a walk error, we append that through
+		if shadowWalkErr != nil {
+			c.shadowErr = multierror.Append(c.shadowErr, shadowWalkErr)
+		}
+
 		if c.shadowErr == nil {
 			log.Printf("[INFO] Shadow graph success!")
 		} else {

terraform/context_apply_test.go

@@ -318,10 +318,10 @@ func TestContext2Apply_computedAttrRefTypeMismatch(t *testing.T) {
 	}
 
 	_, err := ctx.Apply()
-
 	if err == nil {
 		t.Fatalf("Expected err, got none!")
 	}
+
 	expected := "Expected ami to be string"
 	if !strings.Contains(err.Error(), expected) {
 		t.Fatalf("expected:\n\n%s\n\nto contain:\n\n%s", err, expected)

terraform/shadow.go

@@ -0,0 +1,28 @@
+package terraform
+
+// Shadow is the interface that any "shadow" structures must implement.
+//
+// A shadow structure is an interface implementation (typically) that
+// shadows a real implementation and verifies that the same behavior occurs
+// on both. The semantics of this behavior are up to the interface itself.
+//
+// A shadow NEVER modifies real values or state. It must always be safe to use.
+//
+// For example, a ResourceProvider shadow ensures that the same operations
+// are done on the same resources with the same configurations.
+//
+// The typical usage of a shadow following this interface is to complete
+// the real operations, then call CloseShadow which tells the shadow that
+// the real side is done. Then, once the shadow is also complete, call
+// ShadowError to find any errors that may have been caught.
+type Shadow interface {
+	// CloseShadow tells the shadow that the REAL implementation is
+	// complete. Therefore, any calls that would block should now return
+	// immediately since no more changes will happen to the real side.
+	CloseShadow() error
+
+	// ShadowError returns the errors that the shadow has found.
+	// This should be called AFTER CloseShadow and AFTER the shadow is
+	// known to be complete (no more calls to it).
+	ShadowError() error
+}

terraform/shadow_components.go

@@ -112,6 +112,38 @@ func (f *shadowComponentFactory) CloseShadow() error {
 	return result
 }
 
+func (f *shadowComponentFactory) ShadowError() error {
+	// If we aren't the shadow, just return
+	if !f.Shadow {
+		return nil
+	}
+
+	// Lock ourselves so we don't modify state
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
+	// Grab our shared state
+	shared := f.shadowComponentFactoryShared
+
+	// If we're not closed, its an error
+	if !shared.closed {
+		return fmt.Errorf("component factory must be closed to retrieve errors")
+	}
+
+	// Close all the providers and provisioners and return the error
+	var result error
+	for _, n := range shared.providerKeys {
+		_, shadow, err := shared.ResourceProvider(n, n)
+		if err == nil && shadow != nil {
+			if err := shadow.ShadowError(); err != nil {
+				result = multierror.Append(result, err)
+			}
+		}
+	}
+
+	return result
+}
+
 // shadowComponentFactoryShared is shared data between the two factories.
 //
 // It is NOT SAFE to run any function on this struct in parallel. Lock

terraform/shadow_context.go

@@ -2,7 +2,6 @@ package terraform
 
 import (
 	"fmt"
-	"io"
 	"reflect"
 
 	"github.com/hashicorp/go-multierror"
@@ -13,14 +12,13 @@ import (
 // when walking the graph. The resulting context should be used _only once_
 // for a graph walk.
 //
-// The returned io.Closer should be closed after the graph walk with the
-// real context is complete. The result of the Close function will be any
-// errors caught during the shadowing operation.
+// The returned Shadow should be closed after the graph walk with the
+// real context is complete. Errors from the shadow can be retrieved there.
 //
 // Most importantly, any operations done on the shadow context (the returned
 // context) will NEVER affect the real context. All structures are deep
 // copied, no real providers or resources are used, etc.
-func newShadowContext(c *Context) (*Context, *Context, io.Closer) {
+func newShadowContext(c *Context) (*Context, *Context, Shadow) {
 	// Copy the targets
 	targetRaw, err := copystructure.Copy(c.targets)
 	if err != nil {
@@ -99,6 +97,10 @@ type shadowContextCloser struct {
 }
 
 // Close closes the shadow context.
-func (c *shadowContextCloser) Close() error {
+func (c *shadowContextCloser) CloseShadow() error {
 	return c.Components.CloseShadow()
 }
+
+func (c *shadowContextCloser) ShadowError() error {
+	return c.Components.ShadowError()
+}

terraform/shadow_resource_provider.go

@@ -16,14 +16,7 @@ import (
 // be used directly.
 type shadowResourceProvider interface {
 	ResourceProvider
-
-	// CloseShadow should be called when the _real_ side is complete.
-	// This will immediately end any blocked calls and return any errors.
-	//
-	// Any operations on the shadow provider after this is undefined. It
-	// could be fine, it could result in crashes, etc. Do not use the
-	// shadow after this is called.
-	CloseShadow() error
+	Shadow
 }
 
 // newShadowResourceProvider creates a new shadowed ResourceProvider.
@@ -174,6 +167,7 @@ type shadowResourceProviderShared struct {
 	Input            shadow.Value
 	Validate         shadow.Value
 	Configure        shadow.Value
+	ValidateResource shadow.KeyedValue
 	Apply            shadow.KeyedValue
 	Diff             shadow.KeyedValue
 	Refresh          shadow.KeyedValue
@@ -182,7 +176,7 @@ type shadowResourceProviderShared struct {
 func (p *shadowResourceProviderShared) Close() error {
 	closers := []io.Closer{
 		&p.CloseErr, &p.Input, &p.Validate,
-		&p.Configure, &p.Apply, &p.Diff,
+		&p.Configure, &p.ValidateResource, &p.Apply, &p.Diff,
 		&p.Refresh,
 	}
 
@@ -199,13 +193,16 @@ func (p *shadowResourceProviderShared) Close() error {
 }
 
 func (p *shadowResourceProviderShadow) CloseShadow() error {
-	result := p.Error
-	if err := p.Shared.Close(); err != nil {
-		result = multierror.Append(result, fmt.Errorf(
-			"close error: %s", err))
+	err := p.Shared.Close()
+	if err != nil {
+		err = fmt.Errorf("close error: %s", err)
 	}
 
-	return result
+	return err
+}
+
+func (p *shadowResourceProviderShadow) ShadowError() error {
+	return p.Error
 }
 
 func (p *shadowResourceProviderShadow) Resources() []ResourceType {
@@ -313,6 +310,57 @@ func (p *shadowResourceProviderShadow) Configure(c *ResourceConfig) error {
 	return result.Result
 }
 
+func (p *shadowResourceProviderShadow) ValidateResource(t string, c *ResourceConfig) ([]string, []error) {
+	// Unique key
+	key := t
+
+	// Get the initial value
+	raw := p.Shared.ValidateResource.Value(key)
+
+	// Find a validation with our configuration
+	var result *shadowResourceProviderValidateResource
+	for {
+		// Get the value
+		if raw == nil {
+			p.ErrorLock.Lock()
+			defer p.ErrorLock.Unlock()
+			p.Error = multierror.Append(p.Error, fmt.Errorf(
+				"Unknown 'ValidateResource' call for %q:\n\n%#v",
+				key, c))
+			return nil, nil
+		}
+
+		wrapper, ok := raw.(*shadowResourceProviderValidateResourceWrapper)
+		if !ok {
+			p.ErrorLock.Lock()
+			defer p.ErrorLock.Unlock()
+			p.Error = multierror.Append(p.Error, fmt.Errorf(
+				"Unknown 'ValidateResource' shadow value: %#v", raw))
+			return nil, nil
+		}
+
+		// Look for the matching call with our configuration
+		wrapper.RLock()
+		for _, call := range wrapper.Calls {
+			if call.Config.Equal(c) {
+				result = call
+				break
+			}
+		}
+		wrapper.RUnlock()
+
+		// If we found a result, exit
+		if result != nil {
+			break
+		}
+
+		// Wait for a change so we can get the wrapper again
+		raw = p.Shared.ValidateResource.WaitForChange(key)
+	}
+
+	return result.Warns, result.Errors
+}
+
 func (p *shadowResourceProviderShadow) Apply(
 	info *InstanceInfo,
 	state *InstanceState,
@@ -438,10 +486,6 @@ func (p *shadowResourceProviderShadow) Refresh(
 // TODO
 // TODO
 
-func (p *shadowResourceProviderShadow) ValidateResource(t string, c *ResourceConfig) ([]string, []error) {
-	return nil, nil
-}
-
 func (p *shadowResourceProviderShadow) ImportState(info *InstanceInfo, id string) ([]*InstanceState, error) {
 	return nil, nil
 }
@@ -482,6 +526,18 @@ type shadowResourceProviderConfigure struct {
 	Result error
 }
 
+type shadowResourceProviderValidateResourceWrapper struct {
+	sync.RWMutex
+
+	Calls []*shadowResourceProviderValidateResource
+}
+
+type shadowResourceProviderValidateResource struct {
+	Config *ResourceConfig
+	Warns  []string
+	Errors []error
+}
+
 type shadowResourceProviderApply struct {
 	State     *InstanceState
 	Diff      *InstanceDiff

terraform/shadow_resource_provider_test.go

@@ -7,6 +7,10 @@ import (
 	"time"
 )
 
+func TestShadowResourceProvider_impl(t *testing.T) {
+	var _ Shadow = new(shadowResourceProviderShadow)
+}
+
 func TestShadowResourceProvider_cachedValues(t *testing.T) {
 	mock := new(MockResourceProvider)
 	real, shadow := newShadowResourceProvider(mock)