Fix ignored sync work in passive effects (#14799)

* Fix ignored sync work in passive effects

* Fix batching

packages/react-dom/src/__tests__/ReactDOMHooks-test.js

@@ -12,7 +12,7 @@
 let React;
 let ReactDOM;
 
-describe('ReactDOMSuspensePlaceholder', () => {
+describe('ReactDOMHooks', () => {
  let container;
 
  beforeEach(() => {
@@ -29,6 +29,83 @@ describe('ReactDOMSuspensePlaceholder', () => {
  document.body.removeChild(container);
  });
 
+ it('can ReactDOM.render() from useEffect', () => {
+ let container2 = document.createElement('div');
+ let container3 = document.createElement('div');
+
+ function Example1({n}) {
+ React.useEffect(() => {
+ ReactDOM.render(<Example2 n={n} />, container2);
+ });
+ return 1 * n;
+ }
+
+ function Example2({n}) {
+ React.useEffect(() => {
+ ReactDOM.render(<Example3 n={n} />, container3);
+ });
+ return 2 * n;
+ }
+
+ function Example3({n}) {
+ return 3 * n;
+ }
+
+ ReactDOM.render(<Example1 n={1} />, container);
+ expect(container.textContent).toBe('1');
+ expect(container2.textContent).toBe('');
+ expect(container3.textContent).toBe('');
+ jest.runAllTimers();
+ expect(container.textContent).toBe('1');
+ expect(container2.textContent).toBe('2');
+ expect(container3.textContent).toBe('3');
+
+ ReactDOM.render(<Example1 n={2} />, container);
+ expect(container.textContent).toBe('2');
+ expect(container2.textContent).toBe('2'); // Not flushed yet
+ expect(container3.textContent).toBe('3'); // Not flushed yet
+ jest.runAllTimers();
+ expect(container.textContent).toBe('2');
+ expect(container2.textContent).toBe('4');
+ expect(container3.textContent).toBe('6');
+ });
+
+ it('can batch synchronous work inside effects with other work', () => {
+ let otherContainer = document.createElement('div');
+
+ let calledA = false;
+ function A() {
+ calledA = true;
+ return 'A';
+ }
+
+ let calledB = false;
+ function B() {
+ calledB = true;
+ return 'B';
+ }
+
+ let _set;
+ function Foo() {
+ _set = React.useState(0)[1];
+ React.useEffect(() => {
+ ReactDOM.render(<A />, otherContainer);
+ });
+ return null;
+ }
+
+ ReactDOM.render(<Foo />, container);
+ ReactDOM.unstable_batchedUpdates(() => {
+ _set(0); // Forces the effect to be flushed
+ expect(otherContainer.textContent).toBe('');
+ ReactDOM.render(<B />, otherContainer);
+ expect(otherContainer.textContent).toBe('');
+ });
+ expect(otherContainer.textContent).toBe('B');
+ expect(calledA).toBe(false); // It was in a batch
+ expect(calledB).toBe(true);
+ });
+
  it('should not bail out when an update is scheduled from within an event handler', () => {
  const {createRef, useCallback, useState} = React;
 

packages/react-reconciler/src/ReactFiberScheduler.js

@@ -575,6 +575,10 @@ function commitPassiveEffects(root: FiberRoot, firstEffect: Fiber): void {
  if (rootExpirationTime !== NoWork) {
  requestWork(root, rootExpirationTime);
  }
+ // Flush any sync work that was scheduled by effects
+ if (!isBatchingUpdates && !isRendering) {
+ performSyncWork();
+ }
 }
 
 function isAlreadyFailedLegacyErrorBoundary(instance: mixed): boolean {