Add new mock build of Scheduler with flush, yield API (#14964)

* Add new mock build of Scheduler with flush, yield API

Test environments need a way to take control of the Scheduler queue and
incrementally flush work. Our current tests accomplish this either using
dynamic injection, or by using Jest's fake timers feature. Both of these
options are fragile and rely too much on implementation details.

In this new approach, we have a separate build of Scheduler that is
specifically designed for test environments. We mock the default
implementation like we would any other module; in our case, via Jest.
This special build has methods like `flushAll` and `yieldValue` that
control when work is flushed. These methods are based on equivalent
methods we've been using to write incremental React tests. Eventually
we may want to migrate the React tests to interact with the mock
Scheduler directly, instead of going through the host config like we
currently do.

For now, I'm using our custom static injection infrastructure to create
the two builds of Scheduler — a default build for DOM (which falls back
to a naive timer based implementation), and the new mock build. I did it
this way because it allows me to share most of the implementation, which
isn't specific to a host environment — e.g. everything related to the
priority queue. It may be better to duplicate the shared code instead,
especially considering that future environments (like React Native) may
have entirely forked implementations. I'd prefer to wait until the
implementation stabilizes before worrying about that, but I'm open to
changing this now if we decide it's important enough.

* Mock Scheduler in bundle tests, too

* Remove special case by making regex more restrictive

Author: acdlite

packages/jest-mock-scheduler/npm/index.js

@@ -1,7 +1,3 @@
 'use strict';
 
-if (process.env.NODE_ENV === 'production') {
-  module.exports = require('./cjs/jest-mock-scheduler.production.min.js');
-} else {
-  module.exports = require('./cjs/jest-mock-scheduler.development.js');
-}
+module.exports = require('scheduler/unstable_mock');

packages/jest-mock-scheduler/src/JestMockScheduler.js

@@ -13,6 +13,7 @@ const React = require('react');
 let ReactFeatureFlags = require('shared/ReactFeatureFlags');
 
 let ReactDOM;
+let Scheduler;
 
 const ConcurrentMode = React.unstable_ConcurrentMode;
 
@@ -25,33 +26,10 @@ describe('ReactDOMFiberAsync', () => {
   let container;
 
   beforeEach(() => {
-    // TODO pull this into helper method, reduce repetition.
-    // mock the browser APIs which are used in schedule:
-    // - requestAnimationFrame should pass the DOMHighResTimeStamp argument
-    // - calling 'window.postMessage' should actually fire postmessage handlers
-    global.requestAnimationFrame = function(cb) {
-      return setTimeout(() => {
-        cb(Date.now());
-      });
-    };
-    const originalAddEventListener = global.addEventListener;
-    let postMessageCallback;
-    global.addEventListener = function(eventName, callback, useCapture) {
-      if (eventName === 'message') {
-        postMessageCallback = callback;
-      } else {
-        originalAddEventListener(eventName, callback, useCapture);
-      }
-    };
-    global.postMessage = function(messageKey, targetOrigin) {
-      const postMessageEvent = {source: window, data: messageKey};
-      if (postMessageCallback) {
-        postMessageCallback(postMessageEvent);
-      }
-    };
     jest.resetModules();
     container = document.createElement('div');
     ReactDOM = require('react-dom');
+    Scheduler = require('scheduler');
 
     document.body.appendChild(container);
   });
@@ -124,6 +102,7 @@ describe('ReactDOMFiberAsync', () => {
 
     // Should flush both updates now.
     jest.runAllTimers();
+    Scheduler.flushAll();
     expect(asyncValueRef.current.textContent).toBe('hello');
     expect(syncValueRef.current.textContent).toBe('hello');
   });
@@ -133,6 +112,7 @@ describe('ReactDOMFiberAsync', () => {
       jest.resetModules();
       ReactFeatureFlags = require('shared/ReactFeatureFlags');
       ReactDOM = require('react-dom');
+      Scheduler = require('scheduler');
     });
 
     it('renders synchronously', () => {
@@ -160,18 +140,19 @@ describe('ReactDOMFiberAsync', () => {
       ReactFeatureFlags = require('shared/ReactFeatureFlags');
       ReactFeatureFlags.debugRenderPhaseSideEffectsForStrictMode = false;
       ReactDOM = require('react-dom');
+      Scheduler = require('scheduler');
     });
 
     it('createRoot makes the entire tree async', () => {
       const root = ReactDOM.unstable_createRoot(container);
       root.render(<div>Hi</div>);
       expect(container.textContent).toEqual('');
-      jest.runAllTimers();
+      Scheduler.flushAll();
       expect(container.textContent).toEqual('Hi');
 
       root.render(<div>Bye</div>);
       expect(container.textContent).toEqual('Hi');
-      jest.runAllTimers();
+      Scheduler.flushAll();
       expect(container.textContent).toEqual('Bye');
     });
 
@@ -188,12 +169,12 @@ describe('ReactDOMFiberAsync', () => {
       const root = ReactDOM.unstable_createRoot(container);
       root.render(<Component />);
       expect(container.textContent).toEqual('');
-      jest.runAllTimers();
+      Scheduler.flushAll();
       expect(container.textContent).toEqual('0');
 
       instance.setState({step: 1});
       expect(container.textContent).toEqual('0');
-      jest.runAllTimers();
+      Scheduler.flushAll();
       expect(container.textContent).toEqual('1');
     });
 
@@ -213,11 +194,11 @@ describe('ReactDOMFiberAsync', () => {
         </ConcurrentMode>,
         container,
       );
-      jest.runAllTimers();
+      Scheduler.flushAll();
 
       instance.setState({step: 1});
       expect(container.textContent).toEqual('0');
-      jest.runAllTimers();
+      Scheduler.flushAll();
       expect(container.textContent).toEqual('1');
     });
 
@@ -239,11 +220,11 @@ describe('ReactDOMFiberAsync', () => {
         </div>,
         container,
       );
-      jest.runAllTimers();
+      Scheduler.flushAll();
 
       instance.setState({step: 1});
       expect(container.textContent).toEqual('0');
-      jest.runAllTimers();
+      Scheduler.flushAll();
       expect(container.textContent).toEqual('1');
     });
 
@@ -369,7 +350,7 @@ describe('ReactDOMFiberAsync', () => {
         </ConcurrentMode>,
         container,
       );
-      jest.runAllTimers();
+      Scheduler.flushAll();
 
       // Updates are async by default
       instance.push('A');
@@ -392,7 +373,7 @@ describe('ReactDOMFiberAsync', () => {
       expect(ops).toEqual(['BC']);
 
       // Flush the async updates
-      jest.runAllTimers();
+      Scheduler.flushAll();
       expect(container.textContent).toEqual('ABCD');
       expect(ops).toEqual(['BC', 'ABCD']);
     });
@@ -419,7 +400,7 @@ describe('ReactDOMFiberAsync', () => {
       // Test that a normal update is async
       inst.increment();
       expect(container.textContent).toEqual('0');
-      jest.runAllTimers();
+      Scheduler.flushAll();
       expect(container.textContent).toEqual('1');
 
       let ops = [];
@@ -525,7 +506,7 @@ describe('ReactDOMFiberAsync', () => {
       const root = ReactDOM.unstable_createRoot(container);
       root.render(<Form />);
       // Flush
-      jest.runAllTimers();
+      Scheduler.flushAll();
 
       let disableButton = disableButtonRef.current;
       expect(disableButton.tagName).toBe('BUTTON');
@@ -592,7 +573,7 @@ describe('ReactDOMFiberAsync', () => {
       const root = ReactDOM.unstable_createRoot(container);
       root.render(<Form />);
       // Flush
-      jest.runAllTimers();
+      Scheduler.flushAll();
 
       let disableButton = disableButtonRef.current;
       expect(disableButton.tagName).toBe('BUTTON');
@@ -652,7 +633,7 @@ describe('ReactDOMFiberAsync', () => {
       const root = ReactDOM.unstable_createRoot(container);
       root.render(<Form />);
       // Flush
-      jest.runAllTimers();
+      Scheduler.flushAll();
 
       let enableButton = enableButtonRef.current;
       expect(enableButton.tagName).toBe('BUTTON');

packages/react-dom/src/__tests__/ReactDOMFiberAsync-test.internal.js

@@ -11,6 +11,7 @@
 
 let React;
 let ReactDOM;
+let Scheduler;
 
 describe('ReactDOMHooks', () => {
   let container;
@@ -20,6 +21,7 @@ describe('ReactDOMHooks', () => {
 
     React = require('react');
     ReactDOM = require('react-dom');
+    Scheduler = require('scheduler');
 
     container = document.createElement('div');
     document.body.appendChild(container);
@@ -55,7 +57,7 @@ describe('ReactDOMHooks', () => {
     expect(container.textContent).toBe('1');
     expect(container2.textContent).toBe('');
     expect(container3.textContent).toBe('');
-    jest.runAllTimers();
+    Scheduler.flushAll();
     expect(container.textContent).toBe('1');
     expect(container2.textContent).toBe('2');
     expect(container3.textContent).toBe('3');
@@ -64,7 +66,7 @@ describe('ReactDOMHooks', () => {
     expect(container.textContent).toBe('2');
     expect(container2.textContent).toBe('2'); // Not flushed yet
     expect(container3.textContent).toBe('3'); // Not flushed yet
-    jest.runAllTimers();
+    Scheduler.flushAll();
     expect(container.textContent).toBe('2');
     expect(container2.textContent).toBe('4');
     expect(container3.textContent).toBe('6');
@@ -166,14 +168,14 @@ describe('ReactDOMHooks', () => {
       </React.unstable_ConcurrentMode>,
     );
 
-    jest.runAllTimers();
+    Scheduler.flushAll();
 
     inputRef.current.value = 'abc';
     inputRef.current.dispatchEvent(
       new Event('input', {bubbles: true, cancelable: true}),
     );
 
-    jest.runAllTimers();
+    Scheduler.flushAll();
 
     expect(labelRef.current.innerHTML).toBe('abc');
   });