Export React as Named Exports instead of CommonJS (#18106)

* Add options for forked entry points

We currently fork .fb.js entry points. This adds a few more options.

.modern.fb.js - experimental FB builds
.classic.fb.js - stable FB builds
.fb.js - if no other FB build, use this for FB builds
.experimental.js - experimental builds
.stable.js - stable builds
.js - used if no other override exists

This will be used to have different ES exports for different builds.

* Switch React to named exports

* Export named exports from the export point itself

We need to re-export the Flow exported types so we can use them in our code.

We don't want to use the Flow types from upstream since it doesn't have the non-public APIs that we have.

This should be able to use export * but I don't know why it doesn't work.

This actually enables Flow typing of React which was just "any" before.
This exposed some Flow errors that needs fixing.

* Create forks for the react entrypoint

None of our builds expose all exports and they all differ in at least one
way, so we need four forks.

* Set esModule flag to false

We don't want to emit the esModule compatibility flag on our CommonJS
output. For now we treat our named exports as if they're CommonJS.

This is a potentially breaking change for scheduler (but all those apis
are unstable), react-is and use-subscription. However, it seems unlikely
that anyone would rely on this since these only have named exports.

* Remove unused Feature Flags

* Let jest observe the stable fork for stable tests

This lets it do the negative test by ensuring that the right tests fail.

However, this in turn will make other tests that are not behind
__EXPERIMENTAL__ fail. So I need to do that next.

* Put all tests that depend on exports behind __EXPERIMENTAL__

Since there's no way to override the exports using feature flags
in .intern.js anymore we can't use these APIs in stable.

The tradeoff here is that we can either enable the negative tests on
"stable" that means experimental are expected to fail, or we can disable
tests on stable. This is unfortunate since some of these APIs now run on
a "stable" config at FB instead of the experimental.

* Switch ReactDOM to named exports

Same strategy as React.

I moved the ReactDOMFB runtime injection to classic.fb.js

Since we only fork the entrypoint, the `/testing` entrypoint needs to
be forked too to re-export the same things plus `act`. This is a bit
unfortunate. If it becomes a pattern we can consider forking in the
module resolution deeply.

fix flow

* Fix ReactDOM Flow Types

Now that ReactDOM is Flow type checked we need to fix up its types.

* Configure jest to use stable entry for ReactDOM in non-experimental

* Remove additional FeatureFlags that are no longer needed

These are only flagging the exports and no implementation details so we
can control them fully through the export overrides.

packages/react-debug-tools/src/__tests__/ReactHooksInspection-test.internal.js

@@ -22,6 +22,11 @@ describe('ReactHooksInspection', () => {
     ReactDebugTools = require('react-debug-tools');
   });
 
+  if (!__EXPERIMENTAL__) {
+    it("empty test so Jest doesn't complain", () => {});
+    return;
+  }
+
   it('should inspect a simple useResponder hook', () => {
     const TestResponder = React.DEPRECATED_createResponder('TestResponder', {});
 

packages/react-devtools-shared/src/devtools/ContextMenu/useContextMenu.js

@@ -19,18 +19,22 @@ export default function useContextMenu({
 }: {|
   data: Object,
   id: string,
-  ref: ElementRef<HTMLElement>,
+  ref: {current: ElementRef<'div'> | null},
 |}) {
   const {showMenu} = useContext(RegistryContext);
 
   useEffect(() => {
     if (ref.current !== null) {
-      const handleContextMenu = event => {
+      const handleContextMenu = (event: MouseEvent | TouchEvent) => {
         event.preventDefault();
         event.stopPropagation();
 
-        const pageX = event.pageX || (event.touches && event.touches[0].pageX);
-        const pageY = event.pageY || (event.touches && event.touches[0].pageY);
+        const pageX =
+          event.pageX ||
+          (event.touches && ((event: any): TouchEvent).touches[0].pageX);
+        const pageY =
+          event.pageY ||
+          (event.touches && ((event: any): TouchEvent).touches[0].pageY);
 
         showMenu({data, id, pageX, pageY});
       };

packages/react-dom/index.classic.fb.js

@@ -0,0 +1,46 @@
+/**
+ * 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.
+ *
+ * @flow
+ */
+
+import {addUserTimingListener} from 'shared/ReactFeatureFlags';
+import {isEnabled} from './src/events/ReactDOMEventListener';
+import {getClosestInstanceFromNode} from './src/client/ReactDOMComponentTree';
+
+import {__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED} from './src/client/ReactDOM';
+
+// For classic WWW builds, include a few internals that are already in use.
+Object.assign((__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED: any), {
+  ReactBrowserEventEmitter: {
+    isEnabled,
+  },
+  ReactDOMComponentTree: {
+    getClosestInstanceFromNode,
+  },
+  // Perf experiment
+  addUserTimingListener,
+});
+
+export {
+  createPortal,
+  unstable_batchedUpdates,
+  flushSync,
+  __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
+  version,
+  findDOMNode,
+  hydrate,
+  render,
+  unmountComponentAtNode,
+  createRoot,
+  createBlockingRoot,
+  unstable_discreteUpdates,
+  unstable_flushDiscreteUpdates,
+  unstable_flushControlled,
+  unstable_scheduleHydration,
+  unstable_renderSubtreeIntoContainer,
+  unstable_createPortal,
+} from './src/client/ReactDOM';

packages/react-dom/index.experimental.js

@@ -0,0 +1,34 @@
+/**
+ * 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.
+ *
+ * @flow
+ */
+
+export {
+  createPortal,
+  unstable_batchedUpdates,
+  flushSync,
+  __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
+  version,
+  // Disabled behind disableLegacyReactDOMAPIs
+  findDOMNode,
+  hydrate,
+  render,
+  unmountComponentAtNode,
+  // exposeConcurrentModeAPIs
+  createRoot,
+  createBlockingRoot,
+  unstable_discreteUpdates,
+  unstable_flushDiscreteUpdates,
+  unstable_flushControlled,
+  unstable_scheduleHydration,
+  // Disabled behind disableUnstableRenderSubtreeIntoContainer
+  unstable_renderSubtreeIntoContainer,
+  // Disabled behind disableUnstableCreatePortal
+  // Temporary alias since we already shipped React 16 RC with it.
+  // TODO: remove in React 17.
+  unstable_createPortal,
+} from './src/client/ReactDOM';

packages/react-dom/index.js

@@ -7,10 +7,4 @@
  * @flow
  */
 
-'use strict';
-
-const ReactDOM = require('./src/client/ReactDOM');
-
-// TODO: decide on the top-level export form.
-// This is hacky but makes it work with both Rollup and Jest.
-module.exports = ReactDOM.default || ReactDOM;
+export * from './src/client/ReactDOM';

packages/react-dom/index.modern.fb.js

@@ -0,0 +1,22 @@
+/**
+ * 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.
+ *
+ * @flow
+ */
+
+export {
+  createPortal,
+  unstable_batchedUpdates,
+  flushSync,
+  __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
+  version,
+  createRoot,
+  createBlockingRoot,
+  unstable_discreteUpdates,
+  unstable_flushDiscreteUpdates,
+  unstable_flushControlled,
+  unstable_scheduleHydration,
+} from './src/client/ReactDOM';

packages/react-dom/index.stable.js

@@ -0,0 +1,24 @@
+/**
+ * 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.
+ *
+ * @flow
+ */
+
+export {
+  createPortal,
+  unstable_batchedUpdates,
+  flushSync,
+  __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED,
+  version,
+  findDOMNode,
+  hydrate,
+  render,
+  unmountComponentAtNode,
+  unstable_renderSubtreeIntoContainer,
+  // Temporary alias since we already shipped React 16 RC with it.
+  // TODO: remove in React 17.
+  unstable_createPortal,
+} from './src/client/ReactDOM';

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

@@ -13,8 +13,6 @@ const React = require('react');
 const ReactDOM = require('react-dom');
 const PropTypes = require('prop-types');
 
-const ReactFeatureFlags = require('shared/ReactFeatureFlags');
-
 describe('ReactDOMFiber', () => {
   let container;
 
@@ -249,7 +247,7 @@ describe('ReactDOMFiber', () => {
   });
 
   // TODO: remove in React 17
-  if (!ReactFeatureFlags.disableUnstableCreatePortal) {
+  if (!__EXPERIMENTAL__) {
     it('should support unstable_createPortal alias', () => {
       const portalContainer = document.createElement('div');