Use saved plan to determine CreateBeforeDestroy status

terraform/context_apply_test.go

@@ -11847,3 +11847,68 @@ resource "test_resource" "a" {
 		t.Fatalf("apply errors: %s", diags.Err())
 	}
 }
+
+func TestContext2Apply_forcedCBD(t *testing.T) {
+	m := testModuleInline(t, map[string]string{
+		"main.tf": `
+variable "v" {}
+
+resource "test_instance" "a" {
+  require_new = var.v
+}
+
+resource "test_instance" "b" {
+  depends_on = [test_instance.a]
+  lifecycle {
+    create_before_destroy = true
+  }
+}
+`})
+
+	p := testProvider("test")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+
+	ctx := testContext2(t, &ContextOpts{
+		Config: m,
+		Providers: map[addrs.Provider]providers.Factory{
+			addrs.NewDefaultProvider("test"): testProviderFuncFixed(p),
+		},
+		Variables: InputValues{
+			"v": &InputValue{
+				Value: cty.StringVal("A"),
+			},
+		},
+	})
+
+	if _, diags := ctx.Plan(); diags.HasErrors() {
+		t.Fatalf("plan errors: %s", diags.Err())
+	}
+
+	state, diags := ctx.Apply()
+	if diags.HasErrors() {
+		t.Fatalf("apply errors: %s", diags.Err())
+	}
+
+	ctx = testContext2(t, &ContextOpts{
+		Config: m,
+		Providers: map[addrs.Provider]providers.Factory{
+			addrs.NewDefaultProvider("test"): testProviderFuncFixed(p),
+		},
+		Variables: InputValues{
+			"v": &InputValue{
+				Value: cty.StringVal("B"),
+			},
+		},
+		State: state,
+	})
+
+	if _, diags := ctx.Plan(); diags.HasErrors() {
+		t.Fatalf("plan errors: %s", diags.Err())
+	}
+
+	_, diags = ctx.Apply()
+	if diags.HasErrors() {
+		t.Fatalf("apply errors: %s", diags.Err())
+	}
+}

terraform/eval_diff.go

@@ -59,6 +59,18 @@ func (n *EvalCheckPlannedChange) Eval(ctx EvalContext) (interface{}, error) {
 			// all of the unknown values, since the final values might actually
 			// match what was there before after all.
 			log.Printf("[DEBUG] After incorporating new values learned so far during apply, %s change has become NoOp", absAddr)
+
+		case (plannedChange.Action == plans.CreateThenDelete && actualChange.Action == plans.DeleteThenCreate) ||
+			(plannedChange.Action == plans.DeleteThenCreate && actualChange.Action == plans.CreateThenDelete):
+			// If the order of replacement changed, then that is a bug in terraform
+			diags = diags.Append(tfdiags.Sourceless(
+				tfdiags.Error,
+				"Terraform produced inconsistent final plan",
+				fmt.Sprintf(
+					"When expanding the plan for %s to include new values learned so far during apply, the planned action changed from %s to %s.\n\nThis is a bug in Terraform and should be reported.",
+					absAddr, plannedChange.Action, actualChange.Action,
+				),
+			))
 		default:
 			diags = diags.Append(tfdiags.Sourceless(
 				tfdiags.Error,
@@ -118,6 +130,12 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 	provider := *n.Provider
 	providerSchema := *n.ProviderSchema
 
+	createBeforeDestroy := n.CreateBeforeDestroy
+	if n.PreviousDiff != nil {
+		// If we already planned the action, we stick to that plan
+		createBeforeDestroy = (*n.PreviousDiff).Action == plans.CreateThenDelete
+	}
+
 	if providerSchema == nil {
 		return nil, fmt.Errorf("provider schema is unavailable for %s", n.Addr)
 	}
@@ -372,7 +390,7 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 	case !reqRep.Empty():
 		// If there are any "requires replace" paths left _after our filtering
 		// above_ then this is a replace action.
-		if n.CreateBeforeDestroy {
+		if createBeforeDestroy {
 			action = plans.CreateThenDelete
 		} else {
 			action = plans.DeleteThenCreate
@@ -438,7 +456,7 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 	// as a replace change, even though so far we've been treating it as a
 	// create.
 	if action == plans.Create && priorValTainted != cty.NilVal {
-		if n.CreateBeforeDestroy {
+		if createBeforeDestroy {
 			action = plans.CreateThenDelete
 		} else {
 			action = plans.DeleteThenCreate

terraform/node_resource_apply_instance.go

@@ -263,10 +263,15 @@ func (n *NodeApplyableResourceInstance) evalTreeManagedResource(addr addrs.AbsRe
 					destroy := false
 					if diffApply != nil {
 						destroy = (diffApply.Action == plans.Delete || diffApply.Action.IsReplace())
+
+						// Get the stored action for CBD if we have a plan already
+						createBeforeDestroyEnabled = diffApply.Change.Action == plans.CreateThenDelete
 					}
+
 					if destroy && n.CreateBeforeDestroy() {
 						createBeforeDestroyEnabled = true
 					}
+
 					return createBeforeDestroyEnabled, nil
 				},
 				Then: &EvalDeposeState{