terraform: destroy graph must connect edges for proper target ordering

This connects the destroy edges so that when a `-target` is specified on
a destroy, the proper dependencies get destroyed as well.

terraform/context_apply_test.go

@@ -4963,6 +4963,43 @@ aws_instance.bar:
 	`)
 }
 
+func TestContext2Apply_targetedDestroyCountDeps(t *testing.T) {
+	m := testModule(t, "apply-destroy-targeted-count")
+	p := testProvider("aws")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+		State: &State{
+			Modules: []*ModuleState{
+				&ModuleState{
+					Path: rootModulePath,
+					Resources: map[string]*ResourceState{
+						"aws_instance.foo": resourceState("aws_instance", "i-bcd345"),
+						"aws_instance.bar": resourceState("aws_instance", "i-abc123"),
+					},
+				},
+			},
+		},
+		Targets: []string{"aws_instance.foo"},
+		Destroy: true,
+	})
+
+	if _, err := ctx.Plan(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	state, err := ctx.Apply()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	checkStateString(t, state, `<no state>`)
+}
+
 // https://github.com/hashicorp/terraform/issues/4462
 func TestContext2Apply_targetedDestroyModule(t *testing.T) {
 	m := testModule(t, "apply-targeted-module")

terraform/graph_builder_destroy_plan.go

@@ -45,12 +45,17 @@ func (b *DestroyPlanGraphBuilder) Steps() []GraphTransformer {
 			State:    b.State,
 		},
 
-		// Target
-		&TargetsTransformer{Targets: b.Targets},
-
 		// Attach the configuration to any resources
 		&AttachResourceConfigTransformer{Module: b.Module},
 
+		// Destruction ordering. We require this only so that
+		// targeting below will prune the correct things.
+		&DestroyEdgeTransformer{Module: b.Module, State: b.State},
+
+		// Target. Note we don't set "Destroy: true" here since we already
+		// created proper destroy ordering.
+		&TargetsTransformer{Targets: b.Targets},
+
 		// Single root
 		&RootTransformer{},
 	}

terraform/node_resource_plan_destroy.go

@@ -10,6 +10,11 @@ type NodePlanDestroyableResource struct {
 	*NodeAbstractResource
 }
 
+// GraphNodeDestroyer
+func (n *NodePlanDestroyableResource) DestroyAddr() *ResourceAddress {
+	return n.Addr
+}
+
 // GraphNodeEvalable
 func (n *NodePlanDestroyableResource) EvalTree() EvalNode {
 	addr := n.NodeAbstractResource.Addr

terraform/test-fixtures/apply-destroy-targeted-count/main.tf

@@ -0,0 +1,7 @@
+resource "aws_instance" "foo" {
+  count = 3
+}
+
+resource "aws_instance" "bar" {
+  instances = ["${aws_instance.foo.*.id}"]
+}