React.unstable_AsyncComponent (#10239)

Alternative to using the static class property unstable_asyncUpdates.
Everything inside <AsyncComponent /> has async updates by default. You
can also extend it like PureComponent or Component.

scripts/fiber/tests-passing.txt

@@ -674,9 +674,9 @@ src/renderers/dom/fiber/__tests__/ReactDOMFiber-test.js
 src/renderers/dom/fiber/__tests__/ReactDOMFiberAsync-test.js
 * renders synchronously by default
 * renders synchronously when feature flag is disabled
-* unstable_asyncUpdates at the root makes the entire tree async
+* AsyncComponent at the root makes the entire tree async
 * updates inside an async tree are async by default
-* unstable_asyncUpdates creates an async subtree
+* AsyncComponent creates an async subtree
 * updates inside an async subtree are async by default
 
 src/renderers/dom/shared/__tests__/CSSProperty-test.js

src/isomorphic/ReactEntry.js

@@ -40,6 +40,7 @@ var React = {
 
   Component: ReactBaseClasses.Component,
   PureComponent: ReactBaseClasses.PureComponent,
+  unstable_AsyncComponent: ReactBaseClasses.AsyncComponent,
 
   createElement: createElement,
   cloneElement: cloneElement,

src/isomorphic/modern/class/ReactBaseClasses.js

@@ -138,13 +138,33 @@ function ReactPureComponent(props, context, updater) {
 
 function ComponentDummy() {}
 ComponentDummy.prototype = ReactComponent.prototype;
-ReactPureComponent.prototype = new ComponentDummy();
-ReactPureComponent.prototype.constructor = ReactPureComponent;
+var pureComponentPrototype = (ReactPureComponent.prototype = new ComponentDummy());
+pureComponentPrototype.constructor = ReactPureComponent;
 // Avoid an extra prototype jump for these methods.
-Object.assign(ReactPureComponent.prototype, ReactComponent.prototype);
-ReactPureComponent.prototype.isPureReactComponent = true;
+Object.assign(pureComponentPrototype, ReactComponent.prototype);
+pureComponentPrototype.isPureReactComponent = true;
+
+function ReactAsyncComponent(props, context, updater) {
+  // Duplicated from ReactComponent.
+  this.props = props;
+  this.context = context;
+  this.refs = emptyObject;
+  // We initialize the default updater but the real one gets injected by the
+  // renderer.
+  this.updater = updater || ReactNoopUpdateQueue;
+}
+
+var asyncComponentPrototype = (ReactAsyncComponent.prototype = new ComponentDummy());
+asyncComponentPrototype.constructor = ReactAsyncComponent;
+// Avoid an extra prototype jump for these methods.
+Object.assign(asyncComponentPrototype, ReactComponent.prototype);
+asyncComponentPrototype.unstable_isAsyncReactComponent = true;
+asyncComponentPrototype.render = function() {
+  return this.props.children;
+};
 
 module.exports = {
   Component: ReactComponent,
   PureComponent: ReactPureComponent,
+  AsyncComponent: ReactAsyncComponent,
 };

src/renderers/dom/fiber/__tests__/ReactDOMFiberAsync-test.js

@@ -4,6 +4,8 @@ var ReactFeatureFlags = require('ReactFeatureFlags');
 
 var ReactDOM;
 
+var AsyncComponent = React.unstable_AsyncComponent;
+
 describe('ReactDOMFiberAsync', () => {
   var container;
 
@@ -25,16 +27,16 @@ describe('ReactDOMFiberAsync', () => {
 
   if (ReactDOMFeatureFlags.useFiber) {
     it('renders synchronously when feature flag is disabled', () => {
-      class Async extends React.Component {
-        static unstable_asyncUpdates = true;
-        render() {
-          return this.props.children;
-        }
-      }
-      ReactDOM.render(<Async><div>Hi</div></Async>, container);
+      ReactDOM.render(
+        <AsyncComponent><div>Hi</div></AsyncComponent>,
+        container,
+      );
       expect(container.textContent).toEqual('Hi');
 
-      ReactDOM.render(<Async><div>Bye</div></Async>, container);
+      ReactDOM.render(
+        <AsyncComponent><div>Bye</div></AsyncComponent>,
+        container,
+      );
       expect(container.textContent).toEqual('Bye');
     });
 
@@ -47,32 +49,25 @@ describe('ReactDOMFiberAsync', () => {
         ReactDOM = require('react-dom');
       });
 
-      it('unstable_asyncUpdates at the root makes the entire tree async', () => {
-        class Async extends React.Component {
-          static unstable_asyncUpdates = true;
-          render() {
-            return this.props.children;
-          }
-        }
-        ReactDOM.render(<Async><div>Hi</div></Async>, container);
+      it('AsyncComponent at the root makes the entire tree async', () => {
+        ReactDOM.render(
+          <AsyncComponent><div>Hi</div></AsyncComponent>,
+          container,
+        );
         expect(container.textContent).toEqual('');
         jest.runAllTimers();
         expect(container.textContent).toEqual('Hi');
 
-        ReactDOM.render(<Async><div>Bye</div></Async>, container);
+        ReactDOM.render(
+          <AsyncComponent><div>Bye</div></AsyncComponent>,
+          container,
+        );
         expect(container.textContent).toEqual('Hi');
         jest.runAllTimers();
         expect(container.textContent).toEqual('Bye');
       });
 
       it('updates inside an async tree are async by default', () => {
-        class Async extends React.Component {
-          static unstable_asyncUpdates = true;
-          render() {
-            return this.props.children;
-          }
-        }
-
         let instance;
         class Component extends React.Component {
           state = {step: 0};
@@ -82,7 +77,10 @@ describe('ReactDOMFiberAsync', () => {
           }
         }
 
-        ReactDOM.render(<Async><Component /></Async>, container);
+        ReactDOM.render(
+          <AsyncComponent><Component /></AsyncComponent>,
+          container,
+        );
         expect(container.textContent).toEqual('');
         jest.runAllTimers();
         expect(container.textContent).toEqual('0');
@@ -93,11 +91,10 @@ describe('ReactDOMFiberAsync', () => {
         expect(container.textContent).toEqual('1');
       });
 
-      it('unstable_asyncUpdates creates an async subtree', () => {
+      it('AsyncComponent creates an async subtree', () => {
         let instance;
-        class Component extends React.Component {
+        class Component extends React.unstable_AsyncComponent {
           state = {step: 0};
-          static unstable_asyncUpdates = true;
           render() {
             instance = this;
             return <div>{this.state.step}</div>;
@@ -114,8 +111,7 @@ describe('ReactDOMFiberAsync', () => {
       });
 
       it('updates inside an async subtree are async by default', () => {
-        class Component extends React.Component {
-          static unstable_asyncUpdates = true;
+        class Component extends React.unstable_AsyncComponent {
           render() {
             return <Child />;
           }

src/renderers/shared/fiber/ReactFiberClassComponent.js

@@ -388,7 +388,8 @@ module.exports = function(
     if (
       ReactFeatureFlags.enableAsyncSubtreeAPI &&
       workInProgress.type != null &&
-      workInProgress.type.unstable_asyncUpdates === true
+      workInProgress.type.prototype != null &&
+      workInProgress.type.prototype.unstable_isAsyncReactComponent === true
     ) {
       workInProgress.internalContextTag |= AsyncUpdates;
     }

src/renderers/shared/fiber/ReactFiberReconciler.js

@@ -225,7 +225,8 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
       ReactFeatureFlags.enableAsyncSubtreeAPI &&
       element != null &&
       element.type != null &&
-      (element.type: any).unstable_asyncUpdates === true;
+      element.type.prototype != null &&
+      (element.type.prototype: any).unstable_isAsyncReactComponent === true;
     const priorityLevel = getPriorityContext(current, forceAsync);
     const nextState = {element};
     callback = callback === undefined ? null : callback;