terraform: add test to verify orphan outputs in modules are removed

For #7598

This doesn't work with the old graph, we guard it as such.

terraform/context_apply_test.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"github.com/hashicorp/terraform/config/module"
+	"github.com/hashicorp/terraform/helper/experiment"
 )
 
 func TestContext2Apply_basic(t *testing.T) {
@@ -2113,6 +2114,58 @@ func TestContext2Apply_outputOrphan(t *testing.T) {
 	}
 }
 
+func TestContext2Apply_outputOrphanModule(t *testing.T) {
+	if !experiment.Enabled(experiment.X_newApply) {
+		t.SkipNow()
+	}
+
+	m := testModule(t, "apply-output-orphan-module")
+	p := testProvider("aws")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+
+	state := &State{
+		Modules: []*ModuleState{
+			&ModuleState{
+				Path: []string{"root", "child"},
+				Outputs: map[string]*OutputState{
+					"foo": &OutputState{
+						Type:  "string",
+						Value: "bar",
+					},
+					"bar": &OutputState{
+						Type:  "string",
+						Value: "baz",
+					},
+				},
+			},
+		},
+	}
+
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+		State: state,
+	})
+
+	if _, err := ctx.Plan(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	state, err := ctx.Apply()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	actual := strings.TrimSpace(state.String())
+	expected := strings.TrimSpace(testTerraformApplyOutputOrphanModuleStr)
+	if actual != expected {
+		t.Fatalf("bad: \n%s", actual)
+	}
+}
+
 func TestContext2Apply_providerComputedVar(t *testing.T) {
 	m := testModule(t, "apply-provider-computed")
 	p := testProvider("aws")

terraform/terraform_test.go

@@ -501,6 +501,14 @@ Outputs:
 foo = bar
 `
 
+const testTerraformApplyOutputOrphanModuleStr = `
+module.child:
+  <no state>
+  Outputs:
+
+  foo = bar
+`
+
 const testTerraformApplyProvisionerStr = `
 aws_instance.bar:
   ID = foo

terraform/test-fixtures/apply-output-orphan-module/child/main.tf

@@ -0,0 +1 @@
+output "foo" { value = "bar" }

terraform/test-fixtures/apply-output-orphan-module/main.tf

@@ -0,0 +1,3 @@
+module "child" {
+    source = "./child"
+}