terraform: outputs should not be included if not targeted

Fixes #10911

Outputs that aren't targeted shouldn't be included in the graph.

This requires passing targets to the apply graph. This is unfortunate
but long term should be removable since I'd like to move output changes
to the diff as well.

terraform/context.go

@@ -215,6 +215,7 @@ func (c *Context) Graph(typ GraphType, opts *ContextGraphOpts) (*Graph, error) {
 			State:        c.state,
 			Providers:    c.components.ResourceProviders(),
 			Provisioners: c.components.ResourceProvisioners(),
+			Targets:      c.targets,
 			Destroy:      c.destroy,
 			Validate:     opts.Validate,
 		}).Build(RootModulePath)

terraform/context_apply_test.go

@@ -6977,6 +6977,38 @@ module.child:
 	`)
 }
 
+// GH-10911 untargeted outputs should not be in the graph, and therefore
+// not execute.
+func TestContext2Apply_targetedModuleUnrelatedOutputs(t *testing.T) {
+	m := testModule(t, "apply-targeted-module-unrelated-outputs")
+	p := testProvider("aws")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+		Targets: []string{"module.child2"},
+	})
+
+	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>
+module.child2:
+  aws_instance.foo:
+    ID = foo
+	`)
+}
+
 func TestContext2Apply_targetedModuleResource(t *testing.T) {
 	m := testModule(t, "apply-targeted-module-resource")
 	p := testProvider("aws")

terraform/graph_builder_apply.go

@@ -28,6 +28,12 @@ type ApplyGraphBuilder struct {
 	// Provisioners is the list of provisioners supported.
 	Provisioners []string
 
+	// Targets are resources to target. This is only required to make sure
+	// 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
+
 	// DisableReduce, if true, will not reduce the graph. Great for testing.
 	DisableReduce bool
 
@@ -114,6 +120,9 @@ func (b *ApplyGraphBuilder) Steps() []GraphTransformer {
 		// Add the node to fix the state count boundaries
 		&CountBoundaryTransformer{},
 
+		// Target
+		&TargetsTransformer{Targets: b.Targets},
+
 		// Single root
 		&RootTransformer{},
 	}

terraform/graph_builder_apply_test.go

@@ -95,9 +95,7 @@ func TestApplyGraphBuilder_depCbd(t *testing.T) {
 		Modules: []*ModuleDiff{
 			&ModuleDiff{
 				Path: []string{"root"},
-				Resources: map[string]*InstanceDiff{
+				Resources: map[string]*InstanceDiff{"aws_instance.A": &InstanceDiff{Destroy: true,
-					"aws_instance.A": &InstanceDiff{
-						Destroy: true,
 					Attributes: map[string]*ResourceAttrDiff{
 						"name": &ResourceAttrDiff{
 							Old:         "",
@@ -440,6 +438,54 @@ func TestApplyGraphBuilder_provisionerDestroy(t *testing.T) {
 		"null_resource.foo (destroy)")
 }
 
+func TestApplyGraphBuilder_targetModule(t *testing.T) {
+	diff := &Diff{
+		Modules: []*ModuleDiff{
+			&ModuleDiff{
+				Path: []string{"root"},
+				Resources: map[string]*InstanceDiff{
+					"null_resource.foo": &InstanceDiff{
+						Attributes: map[string]*ResourceAttrDiff{
+							"name": &ResourceAttrDiff{
+								Old: "",
+								New: "foo",
+							},
+						},
+					},
+				},
+			},
+
+			&ModuleDiff{
+				Path: []string{"root", "child2"},
+				Resources: map[string]*InstanceDiff{
+					"null_resource.foo": &InstanceDiff{
+						Attributes: map[string]*ResourceAttrDiff{
+							"name": &ResourceAttrDiff{
+								Old: "",
+								New: "foo",
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+
+	b := &ApplyGraphBuilder{
+		Module:    testModule(t, "graph-builder-apply-target-module"),
+		Diff:      diff,
+		Providers: []string{"null"},
+		Targets:   []string{"module.child2"},
+	}
+
+	g, err := b.Build(RootModulePath)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	testGraphNotContains(t, g, "module.child1.output.instance_id")
+}
+
 const testApplyGraphBuilderStr = `
 aws_instance.create
   provider.aws

terraform/node_output.go

@@ -28,6 +28,13 @@ func (n *NodeApplyableOutput) Path() []string {
 	return n.PathValue
 }
 
+// RemovableIfNotTargeted
+func (n *NodeApplyableOutput) RemoveIfNotTargeted() bool {
+	// We need to add this so that this node will be removed if
+	// it isn't targeted or a dependency of a target.
+	return true
+}
+
 // GraphNodeReferenceable
 func (n *NodeApplyableOutput) ReferenceableName() []string {
 	name := fmt.Sprintf("output.%s", n.Config.Name)

terraform/test-fixtures/apply-targeted-module-unrelated-outputs/child1/main.tf

@@ -0,0 +1,10 @@
+variable "instance_id" {
+}
+
+output "instance_id" {
+  value = "${var.instance_id}"
+}
+
+resource "aws_instance" "foo" {
+  foo = "${var.instance_id}"
+}

terraform/test-fixtures/apply-targeted-module-unrelated-outputs/child2/main.tf

@@ -0,0 +1,2 @@
+resource "aws_instance" "foo" {
+}

terraform/test-fixtures/apply-targeted-module-unrelated-outputs/main.tf

@@ -0,0 +1,10 @@
+resource "aws_instance" "foo" {}
+
+module "child1" {
+  source = "./child1"
+  instance_id = "${aws_instance.foo.id}"
+}
+
+module "child2" {
+  source = "./child2"
+}

terraform/test-fixtures/graph-builder-apply-target-module/child1/main.tf

@@ -0,0 +1,12 @@
+variable "instance_id" {
+}
+
+output "instance_id" {
+  value = "${var.instance_id}"
+}
+
+resource "null_resource" "foo" {
+  triggers = {
+    instance_id = "${var.instance_id}"
+  }
+}

terraform/test-fixtures/graph-builder-apply-target-module/child2/main.tf

@@ -0,0 +1,2 @@
+resource "null_resource" "foo" {
+}

terraform/test-fixtures/graph-builder-apply-target-module/main.tf

@@ -0,0 +1,10 @@
+resource "null_resource" "foo" {}
+
+module "child1" {
+  source = "./child1"
+  instance_id = "${null_resource.foo.id}"
+}
+
+module "child2" {
+  source = "./child2"
+}