From 5f4ff0e8be5df05f2ad21f093feb1bb8738ac91b Mon Sep 17 00:00:00 2001
From: James Bardin <j.bardin@gmail.com>
Date: Tue, 17 Nov 2020 09:31:18 -0500
Subject: [PATCH 1/2] don't render plan for module outputs

Module outputs should not trigger plan rendering.
---
 plans/changes.go   |  2 +-
 plans/plan_test.go | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/plans/changes.go b/plans/changes.go
index 414099488..72b6a8938 100644
--- a/plans/changes.go
+++ b/plans/changes.go
@@ -39,7 +39,7 @@ func (c *Changes) Empty() bool {
 	}
 
 	for _, out := range c.Outputs {
-		if out.Action != NoOp {
+		if out.Addr.Module.IsRoot() && out.Action != NoOp {
 			return false
 		}
 	}
diff --git a/plans/plan_test.go b/plans/plan_test.go
index 012ff06a6..b8a0e4501 100644
--- a/plans/plan_test.go
+++ b/plans/plan_test.go
@@ -68,3 +68,28 @@ func TestProviderAddrs(t *testing.T) {
 		t.Error(problem)
 	}
 }
+
+// Module outputs should not effect the result of Empty
+func TestModuleOutputChangesEmpty(t *testing.T) {
+	changes := &Changes{
+		Outputs: []*OutputChangeSrc{
+			{
+				Addr: addrs.AbsOutputValue{
+					Module: addrs.RootModuleInstance.Child("child", addrs.NoKey),
+					OutputValue: addrs.OutputValue{
+						Name: "output",
+					},
+				},
+				ChangeSrc: ChangeSrc{
+					Action: Update,
+					Before: []byte("a"),
+					After:  []byte("b"),
+				},
+			},
+		},
+	}
+
+	if !changes.Empty() {
+		t.Fatal("plan has no visible changes")
+	}
+}

From 8e7a9b6312890a90ef5d9818fc636177807cb475 Mon Sep 17 00:00:00 2001
From: James Bardin <j.bardin@gmail.com>
Date: Tue, 17 Nov 2020 16:11:57 -0500
Subject: [PATCH 2/2] output test for plan with no root output changes

Module outputs do not show up in the plan, and are not rendered in the
UI.
---
 backend/local/backend_plan_test.go            | 50 +++++++++++++++++++
 .../plan-module-outputs-changed/main.tf       |  3 ++
 .../plan-module-outputs-changed/mod/main.tf   |  3 ++
 3 files changed, 56 insertions(+)
 create mode 100644 backend/local/testdata/plan-module-outputs-changed/main.tf
 create mode 100644 backend/local/testdata/plan-module-outputs-changed/mod/main.tf

diff --git a/backend/local/backend_plan_test.go b/backend/local/backend_plan_test.go
index f275d20b1..0b6cc2678 100644
--- a/backend/local/backend_plan_test.go
+++ b/backend/local/backend_plan_test.go
@@ -241,6 +241,56 @@ Changes to Outputs:
 	}
 }
 
+// Module outputs should not cause the plan to be rendered
+func TestLocal_planModuleOutputsChanged(t *testing.T) {
+	b, cleanup := TestLocal(t)
+	defer cleanup()
+	testStateFile(t, b.StatePath, states.BuildState(func(ss *states.SyncState) {
+		ss.SetOutputValue(addrs.AbsOutputValue{
+			Module:      addrs.RootModuleInstance.Child("mod", addrs.NoKey),
+			OutputValue: addrs.OutputValue{Name: "changed"},
+		}, cty.StringVal("before"), false)
+	}))
+	b.CLI = cli.NewMockUi()
+	outDir := testTempDir(t)
+	defer os.RemoveAll(outDir)
+	planPath := filepath.Join(outDir, "plan.tfplan")
+	op, configCleanup := testOperationPlan(t, "./testdata/plan-module-outputs-changed")
+	defer configCleanup()
+	op.PlanRefresh = true
+	op.PlanOutPath = planPath
+	cfg := cty.ObjectVal(map[string]cty.Value{
+		"path": cty.StringVal(b.StatePath),
+	})
+	cfgRaw, err := plans.NewDynamicValue(cfg, cfg.Type())
+	if err != nil {
+		t.Fatal(err)
+	}
+	op.PlanOutBackend = &plans.Backend{
+		Type:   "local",
+		Config: cfgRaw,
+	}
+	run, err := b.Operation(context.Background(), op)
+	if err != nil {
+		t.Fatalf("bad: %s", err)
+	}
+	<-run.Done()
+	if run.Result != backend.OperationSuccess {
+		t.Fatalf("plan operation failed")
+	}
+	if !run.PlanEmpty {
+		t.Fatal("plan should be empty")
+	}
+
+	expectedOutput := strings.TrimSpace(`
+No changes. Infrastructure is up-to-date.
+`)
+	output := b.CLI.(*cli.MockUi).OutputWriter.String()
+	if !strings.Contains(output, expectedOutput) {
+		t.Fatalf("Unexpected output:\n%s\n\nwant output containing:\n%s", output, expectedOutput)
+	}
+}
+
 func TestLocal_planTainted(t *testing.T) {
 	b, cleanup := TestLocal(t)
 	defer cleanup()
diff --git a/backend/local/testdata/plan-module-outputs-changed/main.tf b/backend/local/testdata/plan-module-outputs-changed/main.tf
new file mode 100644
index 000000000..ba8468469
--- /dev/null
+++ b/backend/local/testdata/plan-module-outputs-changed/main.tf
@@ -0,0 +1,3 @@
+module "mod" {
+  source = "./mod"
+}
diff --git a/backend/local/testdata/plan-module-outputs-changed/mod/main.tf b/backend/local/testdata/plan-module-outputs-changed/mod/main.tf
new file mode 100644
index 000000000..cee14bd9c
--- /dev/null
+++ b/backend/local/testdata/plan-module-outputs-changed/mod/main.tf
@@ -0,0 +1,3 @@
+output "changed" {
+  value = "after"
+}