terraform: destroy graph builder, -Xnew-destroy flag

terraform/context.go

@@ -21,6 +21,10 @@ var (
 	// X_newApply will enable the new apply graph. This will be removed
 	// and be on by default in 0.8.0.
 	X_newApply = false
+
+	// X_newDestroy will enable the new destroy graph. This will be removed
+	// and be on by default in 0.8.0.
+	X_newDestroy = false
 )
 
 // InputMode defines what sort of input will be asked for when Input
@@ -371,6 +375,8 @@ func (c *Context) Apply() (*State, error) {
 	// Copy our own state
 	c.state = c.state.DeepCopy()
 
+	newGraphEnabled := (c.destroy && X_newDestroy) || (!c.destroy && X_newApply)
+
 	// Build the original graph. This is before the new graph builders
 	// coming in 0.8. We do this for shadow graphing.
 	oldGraph, err := c.Graph(&ContextGraphOpts{Validate: true})
@@ -386,18 +392,28 @@ func (c *Context) Apply() (*State, error) {
 	}
 
 	// Build the new graph. We do this no matter what so we can shadow it.
-	newGraph, err := (&ApplyGraphBuilder{
-		Module:       c.module,
-		Diff:         c.diff,
-		State:        c.state,
-		Providers:    c.components.ResourceProviders(),
-		Provisioners: c.components.ResourceProvisioners(),
-	}).Build(RootModulePath)
-	if err != nil && !X_newApply {
+	var newGraph *Graph
+	if c.destroy {
+		newGraph, err = (&DestroyApplyGraphBuilder{
+			Module:    c.module,
+			Diff:      c.diff,
+			State:     c.state,
+			Providers: c.providersList(),
+		}).Build(RootModulePath)
+	} else {
+		newGraph, err = (&ApplyGraphBuilder{
+			Module:       c.module,
+			Diff:         c.diff,
+			State:        c.state,
+			Providers:    c.components.ResourceProviders(),
+			Provisioners: c.components.ResourceProvisioners(),
+		}).Build(RootModulePath)
+	}
+	if err != nil && !newGraphEnabled {
 		// If we had an error graphing but we're not using this graph, just
 		// set it to nil and record it as a shadow error.
 		c.shadowErr = multierror.Append(c.shadowErr, fmt.Errorf(
-			"Error building new apply graph: %s", err))
+			"Error building new graph: %s", err))
 
 		newGraph = nil
 		err = nil
@@ -418,16 +434,11 @@ func (c *Context) Apply() (*State, error) {
 	//
 	real := oldGraph
 	shadow := newGraph
-	if c.destroy {
-		log.Printf("[WARN] terraform: real graph is original, shadow is nil")
-		shadow = nil
+	if newGraphEnabled {
+		log.Printf("[WARN] terraform: real graph is experiment, shadow is experiment")
+		real = shadow
 	} else {
-		if X_newApply {
-			log.Printf("[WARN] terraform: real graph is Xnew-apply, shadow is Xnew-apply")
-			real = shadow
-		} else {
-			log.Printf("[WARN] terraform: real graph is original, shadow is Xnew-apply")
-		}
+		log.Printf("[WARN] terraform: real graph is original, shadow is experiment")
 	}
 
 	// For now, always shadow with the real graph for verification. We don't

terraform/graph_builder_destroy_apply.go

@@ -0,0 +1,109 @@
+package terraform
+
+import (
+	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/terraform/dag"
+)
+
+// DestroyApplyGraphBuilder implements GraphBuilder and is responsible for
+// applying a pure-destroy plan.
+//
+// This graph builder is very similar to the ApplyGraphBuilder but
+// is slightly simpler.
+type DestroyApplyGraphBuilder struct {
+	// Module is the root module for the graph to build.
+	Module *module.Tree
+
+	// Diff is the diff to apply.
+	Diff *Diff
+
+	// State is the current state
+	State *State
+
+	// Providers is the list of providers supported.
+	Providers []string
+
+	// DisableReduce, if true, will not reduce the graph. Great for testing.
+	DisableReduce bool
+}
+
+// See GraphBuilder
+func (b *DestroyApplyGraphBuilder) Build(path []string) (*Graph, error) {
+	return (&BasicGraphBuilder{
+		Steps:    b.Steps(),
+		Validate: true,
+	}).Build(path)
+}
+
+// See GraphBuilder
+func (b *DestroyApplyGraphBuilder) Steps() []GraphTransformer {
+	// Custom factory for creating providers.
+	providerFactory := func(name string, path []string) GraphNodeProvider {
+		return &NodeApplyableProvider{
+			NameValue: name,
+			PathValue: path,
+		}
+	}
+
+	concreteResource := func(a *NodeAbstractResource) dag.Vertex {
+		return &NodeApplyableResource{
+			NodeAbstractResource: a,
+		}
+	}
+
+	steps := []GraphTransformer{
+		// Creates all the nodes represented in the diff.
+		&DiffTransformer{
+			Concrete: concreteResource,
+
+			Diff:   b.Diff,
+			Module: b.Module,
+			State:  b.State,
+		},
+
+		// Create orphan output nodes
+		&OrphanOutputTransformer{Module: b.Module, State: b.State},
+
+		// Attach the configuration to any resources
+		&AttachResourceConfigTransformer{Module: b.Module},
+
+		// Attach the state
+		&AttachStateTransformer{State: b.State},
+
+		// Destruction ordering. NOTE: For destroys, we don't need to
+		// do any CBD stuff, so that is explicitly not here.
+		&DestroyEdgeTransformer{Module: b.Module, State: b.State},
+
+		// Create all the providers
+		&MissingProviderTransformer{Providers: b.Providers, Factory: providerFactory},
+		&ProviderTransformer{},
+		&ParentProviderTransformer{},
+		&AttachProviderConfigTransformer{Module: b.Module},
+
+		// Add root variables
+		&RootVariableTransformer{Module: b.Module},
+
+		// Add module variables
+		&ModuleVariableTransformer{Module: b.Module},
+
+		// Add the outputs
+		&OutputTransformer{Module: b.Module},
+
+		// Connect references so ordering is correct
+		&ReferenceTransformer{},
+
+		// Add the node to fix the state count boundaries
+		&CountBoundaryTransformer{},
+
+		// Single root
+		&RootTransformer{},
+	}
+
+	if !b.DisableReduce {
+		// Perform the transitive reduction to make our graph a bit
+		// more sane if possible (it usually is possible).
+		steps = append(steps, &TransitiveReductionTransformer{})
+	}
+
+	return steps
+}

terraform/terraform_test.go

@@ -24,6 +24,7 @@ const fixtureDir = "./test-fixtures"
 func TestMain(m *testing.M) {
 	// Experimental features
 	xNewApply := flag.Bool("Xnew-apply", false, "Experiment: new apply graph")
+	xNewDestroy := flag.Bool("Xnew-destroy", false, "Experiment: new destroy graph")
 
 	// Normal features
 	shadow := flag.Bool("shadow", true, "Enable shadow graph")
@@ -32,6 +33,7 @@ func TestMain(m *testing.M) {
 
 	// Setup experimental features
 	X_newApply = *xNewApply
+	X_newDestroy = *xNewDestroy
 
 	if testing.Verbose() {
 		// if we're verbose, use the logging requested by TF_LOG