detect new outputs and plans as Create actions

Rather than using a prior value of null to indicate create, which is
imprecise because null is a valid output value, only plan values that
didn't exist in the prior state as Create changes.

terraform/context_plan_test.go

@@ -6714,3 +6714,29 @@ output "planned" {
 		}
 	}
 }
+
+func TestContext2Plan_createOutput(t *testing.T) {
+	// this should always plan a NoOp change for the output
+	m := testModuleInline(t, map[string]string{
+		"main.tf": `
+output "planned" {
+  value = 1
+}
+`,
+	})
+
+	ctx := testContext2(t, &ContextOpts{
+		Config: m,
+		State:  states.NewState(),
+	})
+	plan, diags := ctx.Plan()
+	if diags.HasErrors() {
+		t.Fatal(diags.Err())
+	}
+
+	for _, c := range plan.Changes.Outputs {
+		if c.Action != plans.Create {
+			t.Fatalf("expected Create change, got %s for %q", c.Action, c.Addr)
+		}
+	}
+}

terraform/node_output.go

@@ -432,12 +432,17 @@ func (n *NodeApplyableOutput) setValue(state *states.SyncState, changes *plans.C
 		// the diff
 		sensitiveBefore := false
 		before := cty.NullVal(cty.DynamicPseudoType)
+
+		// is this output new to our state?
+		newOutput := true
+
 		mod := state.Module(n.Addr.Module)
 		if n.Addr.Module.IsRoot() && mod != nil {
 			for name, o := range mod.OutputValues {
 				if name == n.Addr.OutputValue.Name {
 					before = o.Value
 					sensitiveBefore = o.Sensitive
+					newOutput = false
 					break
 				}
 			}
@@ -455,10 +460,11 @@ func (n *NodeApplyableOutput) setValue(state *states.SyncState, changes *plans.C
 		switch {
 		case val.IsNull() && before.IsNull():
 			// This is separate from the NoOp case below, since we can ignore
-			// sensitivity here if there are only null values.
+			// sensitivity here when there are only null values.
 			action = plans.NoOp
 
-		case before.IsNull():
+		case newOutput:
+			// This output was just added to the configuration
 			action = plans.Create
 
 		case val.IsWhollyKnown() &&