Deletion effects should fire parent -> child

packages/react-reconciler/src/ReactFiberCommitWork.new.js

@@ -2005,6 +2005,13 @@ function commitPassiveUnmountEffectsInsideOfDeletedTree_begin(
 ) {
   while (nextEffect !== null) {
     const fiber = nextEffect;
+
+    // Deletion effects fire in parent -> child order
+    // TODO: Check if fiber has a PassiveStatic flag
+    setCurrentDebugFiberInDEV(fiber);
+    commitPassiveUnmountInsideDeletedTreeOnFiber(fiber);
+    resetCurrentDebugFiberInDEV();
+
     const child = fiber.child;
     // TODO: Only traverse subtree if it has a PassiveStatic flag
     if (child !== null) {
@@ -2023,11 +2030,6 @@ function commitPassiveUnmountEffectsInsideOfDeletedTree_complete(
 ) {
   while (nextEffect !== null) {
     const fiber = nextEffect;
-    // TODO: Check if fiber has a PassiveStatic flag
-    setCurrentDebugFiberInDEV(fiber);
-    commitPassiveUnmountInsideDeletedTreeOnFiber(fiber);
-    resetCurrentDebugFiberInDEV();
-
     if (fiber === deletedSubtreeRoot) {
       nextEffect = null;
       return;

packages/react-reconciler/src/ReactFiberCommitWork.old.js

@@ -2005,6 +2005,13 @@ function commitPassiveUnmountEffectsInsideOfDeletedTree_begin(
 ) {
   while (nextEffect !== null) {
     const fiber = nextEffect;
+
+    // Deletion effects fire in parent -> child order
+    // TODO: Check if fiber has a PassiveStatic flag
+    setCurrentDebugFiberInDEV(fiber);
+    commitPassiveUnmountInsideDeletedTreeOnFiber(fiber);
+    resetCurrentDebugFiberInDEV();
+
     const child = fiber.child;
     // TODO: Only traverse subtree if it has a PassiveStatic flag
     if (child !== null) {
@@ -2023,11 +2030,6 @@ function commitPassiveUnmountEffectsInsideOfDeletedTree_complete(
 ) {
   while (nextEffect !== null) {
     const fiber = nextEffect;
-    // TODO: Check if fiber has a PassiveStatic flag
-    setCurrentDebugFiberInDEV(fiber);
-    commitPassiveUnmountInsideDeletedTreeOnFiber(fiber);
-    resetCurrentDebugFiberInDEV();
-
     if (fiber === deletedSubtreeRoot) {
       nextEffect = null;
       return;

packages/react-reconciler/src/__tests__/ReactEffectOrdering-test.js

@@ -0,0 +1,86 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails react-core
+ * @jest-environment node
+ */
+
+/* eslint-disable no-func-assign */
+
+'use strict';
+
+let React;
+let ReactNoop;
+let Scheduler;
+let useEffect;
+let useLayoutEffect;
+
+describe('ReactHooksWithNoopRenderer', () => {
+  beforeEach(() => {
+    jest.resetModules();
+    jest.useFakeTimers();
+
+    React = require('react');
+    ReactNoop = require('react-noop-renderer');
+    Scheduler = require('scheduler');
+    useEffect = React.useEffect;
+    useLayoutEffect = React.useLayoutEffect;
+  });
+
+  test('layout unmmouts on deletion are fired in parent -> child order', async () => {
+    const root = ReactNoop.createRoot();
+
+    function Parent() {
+      useLayoutEffect(() => {
+        return () => Scheduler.unstable_yieldValue('Unmount parent');
+      });
+      return <Child />;
+    }
+
+    function Child() {
+      useLayoutEffect(() => {
+        return () => Scheduler.unstable_yieldValue('Unmount child');
+      });
+      return 'Child';
+    }
+
+    await ReactNoop.act(async () => {
+      root.render(<Parent />);
+    });
+    expect(root).toMatchRenderedOutput('Child');
+    await ReactNoop.act(async () => {
+      root.render(null);
+    });
+    expect(Scheduler).toHaveYielded(['Unmount parent', 'Unmount child']);
+  });
+
+  test('passive unmmouts on deletion are fired in parent -> child order', async () => {
+    const root = ReactNoop.createRoot();
+
+    function Parent() {
+      useEffect(() => {
+        return () => Scheduler.unstable_yieldValue('Unmount parent');
+      });
+      return <Child />;
+    }
+
+    function Child() {
+      useEffect(() => {
+        return () => Scheduler.unstable_yieldValue('Unmount child');
+      });
+      return 'Child';
+    }
+
+    await ReactNoop.act(async () => {
+      root.render(<Parent />);
+    });
+    expect(root).toMatchRenderedOutput('Child');
+    await ReactNoop.act(async () => {
+      root.render(null);
+    });
+    expect(Scheduler).toHaveYielded(['Unmount parent', 'Unmount child']);
+  });
+});