[react-testing] fixed react queue emptying for React 17

.changeset/great-comics-appear.md

@@ -0,0 +1,5 @@
+---
+'@shopify/react-testing': patch
+---
+
+Fix act queue emptying for React 17

packages/react-testing/src/compat.ts

@@ -1,4 +1,5 @@
 import ReactDOM from 'react-dom';
+import React from 'react';
 import type {Root as ReactRoot} from 'react-dom/client';
 
 import {ReactInstance, Fiber} from './types';
@@ -34,3 +35,32 @@ export function createRoot(element: HTMLElement): ReactRoot {
     return createRootShim(element);
   }
 }
+
+export const isLegacyReact = parseInt(React.version, 10) < 18;
+
+// https://github.com/facebook/react/blob/12adaffef7105e2714f82651ea51936c563fe15c/packages/shared/enqueueTask.js#L13
+let enqueueTaskImpl: any = null;
+
+export function enqueueTask(task: (v: any) => void) {
+  if (enqueueTaskImpl === null) {
+    try {
+      // read require off the module object to get around the bundlers.
+      // we don't want them to detect a require and bundle a Node polyfill.
+      const requireString = `require${Math.random()}`.slice(0, 7);
+      const nodeRequire = module && module[requireString];
+      // assuming we're in node, let's try to get node's
+      // version of setImmediate, bypassing fake timers if any.
+      enqueueTaskImpl = nodeRequire.call(module, 'timers').setImmediate;
+    } catch (_err) {
+      // we're in a browser
+      // we can't use regular timers because they may still be faked
+      // so we try MessageChannel+postMessage instead
+      enqueueTaskImpl = function (callback: () => void) {
+        const channel = new MessageChannel();
+        channel.port1.onmessage = callback;
+        channel.port2.postMessage(undefined);
+      };
+    }
+  }
+  return enqueueTaskImpl!(task);
+}

packages/react-testing/src/root.tsx

@@ -5,7 +5,7 @@ import {act} from 'react-dom/test-utils';
 
 import {TestWrapper} from './TestWrapper';
 import {Element} from './element';
-import {createRoot, getInternals} from './compat';
+import {createRoot, getInternals, enqueueTask, isLegacyReact} from './compat';
 import {
   Tag,
   Fiber,
@@ -313,6 +313,11 @@ export class Root<Props> implements Node<Props> {
     this.destroyed = true;
     await mountedPromise;
     this.actCallbacks.forEach((callback) => callback());
+
+    if (isLegacyReact) {
+      // flush macro task for react 17 only
+      await new Promise((resolve) => enqueueTask(resolve));
+    }
   }
 
   setProps(props: Partial<Props>) {

packages/react-testing/src/tests/e2e.test.tsx

@@ -15,8 +15,6 @@ import {createPortal} from 'react-dom';
 
 import {mount, createMount} from '../mount';
 
-const itIf = (condition) => (condition ? it : it.skip);
-
 describe('@shopify/react-testing', () => {
   it('does not time out with large trees', () => {
     function RecurseMyself({times}: {times: number}) {
@@ -175,35 +173,28 @@ describe('@shopify/react-testing', () => {
       );
     }
 
-    // eslint-disable-next-line no-process-env
-    itIf(process.env.REACT_VERSION !== '17')(
-      'releases any stale promises when component is destroyed',
-      async () => {
-        const wrapper = mount(<Counter />);
-        wrapper.act(() => new Promise(() => {}));
-        wrapper.act(() => new Promise(() => {}));
-        await wrapper.destroy();
-
-        // React 17 will fail without this await
-        await new Promise((resolve) => setTimeout(resolve, 0));
+    it('releases any stale promises when component is destroyed', async () => {
+      const wrapper = mount(<Counter />);
+      wrapper.act(() => new Promise(() => {}));
+      wrapper.act(() => new Promise(() => {}));
+      await wrapper.destroy();
 
-        function EffectChangeComponent({children}: {children?: ReactNode}) {
-          const [counter, setCounter] = useState(0);
-          useEffect(() => setCounter(100), []);
+      function EffectChangeComponent({children}: {children?: ReactNode}) {
+        const [counter, setCounter] = useState(0);
+        useEffect(() => setCounter(100), []);
 
-          return (
-            // eslint-disable-next-line @shopify/jsx-prefer-fragment-wrappers
-            <div>
-              <Message>{counter}</Message>
-              {children}
-            </div>
-          );
-        }
-        const newWrapper = mount(<EffectChangeComponent />);
+        return (
+          // eslint-disable-next-line @shopify/jsx-prefer-fragment-wrappers
+          <div>
+            <Message>{counter}</Message>
+            {children}
+          </div>
+        );
+      }
+      const newWrapper = mount(<EffectChangeComponent />);
 
-        expect(newWrapper.find(Message)!.html()).toBe('<span>100</span>');
-      },
-    );
+      expect(newWrapper.find(Message)!.html()).toBe('<span>100</span>');
+    });
 
     it('updates element tree when state is changed', () => {
       const wrapper = mount(<Counter />);