Use testing builds for our own tests

Following up from facebook#17915 where we generated testing builds for `react-dom`, this PR uses those builds for our own tests.

- fixes `ReactFeatureFlags.testing` to use all the default flags
- changes `ReactFeatureFlags.readonly` to return `isTestEnvironment: true` (this might not strictly be needed)
- with jest, mocks `react-dom` with the testing version, both for source and builds
- uses `ReactDOM.act` in one of these tests to verify it actually works

fixtures/dom/src/__tests__/nested-act-test.js

@@ -13,10 +13,7 @@ let TestRenderer;
 
 global.__DEV__ = process.env.NODE_ENV !== 'production';
 
-jest.mock('react-dom', () =>
-  require.requireActual('react-dom/cjs/react-dom-testing.development.js')
-);
-// we'll replace the above with react/testing and react-dom/testing right before the next minor
+jest.mock('react-dom', () => require.requireActual('react-dom/testing'));
 
 expect.extend(require('../toWarnDev'));
 

fixtures/dom/src/__tests__/wrong-act-test.js

@@ -18,10 +18,7 @@ let ARTTest;
 global.__DEV__ = process.env.NODE_ENV !== 'production';
 global.__EXPERIMENTAL__ = process.env.RELEASE_CHANNEL === 'experimental';
 
-jest.mock('react-dom', () =>
-  require.requireActual('react-dom/cjs/react-dom-testing.development.js')
-);
-// we'll replace the above with react/testing and react-dom/testing right before the next minor
+jest.mock('react-dom', () => require.requireActual('react-dom/testing'));
 
 expect.extend(require('../toWarnDev'));
 

packages/react-dom/package.json

@@ -30,6 +30,7 @@
     "README.md",
     "build-info.json",
     "index.js",
+    "testing.js",
     "profiling.js",
     "server.js",
     "server.browser.js",

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

@@ -13,7 +13,6 @@ let React;
 let ReactDOM;
 let Suspense;
 let ReactCache;
-let ReactTestUtils;
 let Scheduler;
 let TextResource;
 let act;
@@ -26,9 +25,8 @@ describe('ReactDOMSuspensePlaceholder', () => {
     React = require('react');
     ReactDOM = require('react-dom');
     ReactCache = require('react-cache');
-    ReactTestUtils = require('react-dom/test-utils');
     Scheduler = require('scheduler');
-    act = ReactTestUtils.act;
+    act = ReactDOM.act;
     Suspense = React.Suspense;
     container = document.createElement('div');
     document.body.appendChild(container);

packages/react-dom/testing.fb.js

@@ -0,0 +1,14 @@
+/**
+ * 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.
+ */
+
+'use strict';
+
+const ReactDOMFB = require('./src/client/ReactDOMFB');
+
+// TODO: decide on the top-level export form.
+// This is hacky but makes it work with both Rollup and Jest.
+module.exports = ReactDOMFB.default || ReactDOMFB;

packages/shared/ReactFeatureFlags.js

@@ -7,6 +7,11 @@
  * @flow strict
  */
 
+/*
+  SYNC WITH forks/ReactFeatureFlags.testing.js
+  except isTestEnvironment = true
+*/
+
 export const enableUserTimingAPI = __DEV__;
 
 // Helps identify side effects in render-phase lifecycle hooks and setState

packages/shared/forks/ReactFeatureFlags.readonly.js

@@ -9,4 +9,4 @@
 // It lets us determine whether we're running in Fire mode without making tests internal.
 const ReactFeatureFlags = require('../ReactFeatureFlags');
 // Forbid writes because this wouldn't work with bundle tests.
-module.exports = Object.freeze({...ReactFeatureFlags});
+module.exports = Object.freeze({...ReactFeatureFlags, isTestEnvironment: true});

packages/shared/forks/ReactFeatureFlags.test-renderer.js

@@ -47,7 +47,7 @@ export const disableUnstableRenderSubtreeIntoContainer = false;
 export const warnUnstableRenderSubtreeIntoContainer = false;
 export const disableUnstableCreatePortal = false;
 export const deferPassiveEffectCleanupDuringUnmount = false;
-export const isTestEnvironment = true; // this should probably *never* change
+export const isTestEnvironment = true;
 
 // Only used in www builds.
 export function addUserTimingListener() {

packages/shared/forks/ReactFeatureFlags.test-renderer.www.js

@@ -45,7 +45,7 @@ export const disableUnstableRenderSubtreeIntoContainer = false;
 export const warnUnstableRenderSubtreeIntoContainer = false;
 export const disableUnstableCreatePortal = false;
 export const deferPassiveEffectCleanupDuringUnmount = false;
-export const isTestEnvironment = true; // this should probably *never* change
+export const isTestEnvironment = true;
 
 // Only used in www builds.
 export function addUserTimingListener() {

packages/shared/forks/ReactFeatureFlags.testing.js

@@ -4,58 +4,131 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @flow
+ * @flow strict
  */
 
-import invariant from 'shared/invariant';
+/*
+  SYNC WITH ReactFeatureFlags.js
+  except isTestEnvironment = true
+*/
 
-import typeof * as FeatureFlagsType from 'shared/ReactFeatureFlags';
-import typeof * as PersistentFeatureFlagsType from './ReactFeatureFlags.persistent';
-
-export const debugRenderPhaseSideEffectsForStrictMode = false;
 export const enableUserTimingAPI = __DEV__;
+
+// Helps identify side effects in render-phase lifecycle hooks and setState
+// reducers by double invoking them in Strict Mode.
+export const debugRenderPhaseSideEffectsForStrictMode = __DEV__;
+
+// To preserve the "Pause on caught exceptions" behavior of the debugger, we
+// replay the begin phase of a failed component inside invokeGuardedCallback.
+export const replayFailedUnitOfWorkWithInvokeGuardedCallback = __DEV__;
+
+// Warn about deprecated, async-unsafe lifecycles; relates to RFC #6:
 export const warnAboutDeprecatedLifecycles = true;
-export const replayFailedUnitOfWorkWithInvokeGuardedCallback = false;
+
+// Gather advanced timing metrics for Profiler subtrees.
 export const enableProfilerTimer = __PROFILE__;
+
+// Trace which interactions trigger each commit.
 export const enableSchedulerTracing = __PROFILE__;
-export const enableSuspenseServerRenderer = false;
-export const enableSelectiveHydration = false;
-export const enableChunksAPI = false;
+
+// SSR experiments
+export const enableSuspenseServerRenderer = __EXPERIMENTAL__;
+export const enableSelectiveHydration = __EXPERIMENTAL__;
+
+// Flight experiments
+export const enableChunksAPI = __EXPERIMENTAL__;
+
+// Only used in www builds.
+export const enableSchedulerDebugging = false;
+
+// Only used in www builds.
+export function addUserTimingListener() {
+  throw new Error('Not implemented.');
+}
+
+// Disable javascript: URL strings in href for XSS protection.
 export const disableJavaScriptURLs = false;
-export const disableInputAttributeSyncing = false;
+
+// These APIs will no longer be "unstable" in the upcoming 16.7 release,
+// Control this behavior with a flag to support 16.6 minor releases in the meanwhile.
 export const exposeConcurrentModeAPIs = __EXPERIMENTAL__;
+
 export const warnAboutShorthandPropertyCollision = false;
-export const enableSchedulerDebugging = false;
+
+// Experimental React Flare event system and event components support.
 export const enableDeprecatedFlareAPI = false;
+
+// Experimental Host Component support.
 export const enableFundamentalAPI = false;
+
+// Experimental Scope support.
 export const enableScopeAPI = false;
+
+// New API for JSX transforms to target - https://github.com/reactjs/rfcs/pull/107
 export const enableJSXTransformAPI = false;
+
+// We will enforce mocking scheduler with scheduler/unstable_mock at some point. (v17?)
+// Till then, we warn about the missing mock, but still fallback to a legacy mode compatible version
 export const warnAboutUnmockedScheduler = false;
+
+// For tests, we flush suspense fallbacks in an act scope;
+// *except* in some of our own tests, where we test incremental loading states.
 export const flushSuspenseFallbacksInTests = true;
+
+// Add a callback property to suspense to notify which promises are currently
+// in the update queue. This allows reporting and tracing of what is causing
+// the user to see a loading state.
+// Also allows hydration callbacks to fire when a dehydrated boundary gets
+// hydrated or deleted.
 export const enableSuspenseCallback = false;
+
+// Part of the simplification of React.createElement so we can eventually move
+// from React.createElement to React.jsx
+// https://github.com/reactjs/rfcs/blob/createlement-rfc/text/0000-create-element-changes.md
 export const warnAboutDefaultPropsOnFunctionComponents = false;
-export const warnAboutStringRefs = false;
-export const disableLegacyContext = false;
+
 export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
+
 export const enableTrainModelFix = true;
+
 export const enableTrustedTypesIntegration = false;
+
+// Flag to turn event.target and event.currentTarget in ReactNative from a reactTag to a component instance
 export const enableNativeTargetAsInstance = false;
+
+// Controls behavior of deferred effect destroy functions during unmount.
+// Previously these functions were run during commit (along with layout effects).
+// Ideally we should delay these until after commit for performance reasons.
+// This flag provides a killswitch if that proves to break existing code somehow.
+export const deferPassiveEffectCleanupDuringUnmount = false;
+
+export const isTestEnvironment = true;
+
+// --------------------------
+// Future APIs to be deprecated
+// --------------------------
+
+// Prevent the value and checked attributes from syncing
+// with their related DOM properties
+export const disableInputAttributeSyncing = false;
+
+export const warnAboutStringRefs = false;
+
+export const disableLegacyContext = false;
+
+// Disables React.createFactory
 export const disableCreateFactory = false;
+
+// Disables children for <textarea> elements
 export const disableTextareaChildren = false;
+
+// Disables Maps as ReactElement children
 export const disableMapsAsChildren = false;
+
+// Disables ReactDOM.unstable_renderSubtreeIntoContainer
 export const disableUnstableRenderSubtreeIntoContainer = false;
+// We should remove this flag once the above flag becomes enabled
 export const warnUnstableRenderSubtreeIntoContainer = false;
-export const disableUnstableCreatePortal = false;
-export const deferPassiveEffectCleanupDuringUnmount = false;
-export const isTestEnvironment = true;
 
-// Only used in www builds.
-export function addUserTimingListener() {
-  invariant(false, 'Not implemented.');
-}
-
-// Flow magic to verify the exports of this file match the original version.
-// eslint-disable-next-line no-unused-vars
-type Check<_X, Y: _X, X: Y = _X> = null;
-// eslint-disable-next-line no-unused-expressions
-(null: Check<PersistentFeatureFlagsType, FeatureFlagsType>);
+// Disables ReactDOM.unstable_createPortal
+export const disableUnstableCreatePortal = false;

packages/shared/forks/ReactFeatureFlags.testing.www.js

@@ -0,0 +1,118 @@
+/**
+ * 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
+ */
+
+/*
+  SYNC WITH forks/ReactFeatureFlags.www.js
+  except isTestEnvironment = true
+*/
+
+import typeof * as FeatureFlagsType from 'shared/ReactFeatureFlags';
+import typeof * as FeatureFlagsShimType from './ReactFeatureFlags.www';
+
+// Re-export dynamic flags from the www version.
+export const {
+  debugRenderPhaseSideEffectsForStrictMode,
+  disableInputAttributeSyncing,
+  enableTrustedTypesIntegration,
+  deferPassiveEffectCleanupDuringUnmount,
+} = require('ReactFeatureFlags');
+
+// In www, we have experimental support for gathering data
+// from User Timing API calls in production. By default, we
+// only emit performance.mark/measure calls in __DEV__. But if
+// somebody calls addUserTimingListener() which is exposed as an
+// experimental FB-only export, we call performance.mark/measure
+// as long as there is more than a single listener.
+export let enableUserTimingAPI = __DEV__;
+
+export const enableProfilerTimer = __PROFILE__;
+export const enableSchedulerTracing = __PROFILE__;
+export const enableSchedulerDebugging = true;
+
+export const replayFailedUnitOfWorkWithInvokeGuardedCallback = false;
+export const warnAboutDeprecatedLifecycles = true;
+export const warnAboutShorthandPropertyCollision = false;
+export const disableLegacyContext = false;
+export const warnAboutStringRefs = false;
+export const warnAboutDefaultPropsOnFunctionComponents = false;
+export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
+
+export const enableTrainModelFix = true;
+
+export const exposeConcurrentModeAPIs = __EXPERIMENTAL__;
+
+export const enableSuspenseServerRenderer = true;
+export const enableSelectiveHydration = true;
+
+export const enableChunksAPI = __EXPERIMENTAL__;
+
+export const disableJavaScriptURLs = true;
+
+let refCount = 0;
+export function addUserTimingListener() {
+  if (__DEV__) {
+    // Noop.
+    return () => {};
+  }
+  refCount++;
+  updateFlagOutsideOfReactCallStack();
+  return () => {
+    refCount--;
+    updateFlagOutsideOfReactCallStack();
+  };
+}
+
+// The flag is intentionally updated in a timeout.
+// We don't support toggling it during reconciliation or
+// commit since that would cause mismatching user timing API calls.
+let timeout = null;
+function updateFlagOutsideOfReactCallStack() {
+  if (!timeout) {
+    timeout = setTimeout(() => {
+      timeout = null;
+      enableUserTimingAPI = refCount > 0;
+    });
+  }
+}
+
+export const enableDeprecatedFlareAPI = true;
+
+export const enableFundamentalAPI = false;
+
+export const enableScopeAPI = true;
+
+export const enableJSXTransformAPI = true;
+
+export const warnAboutUnmockedScheduler = true;
+
+export const enableSuspenseCallback = true;
+
+export const flushSuspenseFallbacksInTests = true;
+
+export const enableNativeTargetAsInstance = false;
+
+export const disableCreateFactory = false;
+
+export const disableTextareaChildren = false;
+
+export const disableMapsAsChildren = false;
+
+export const disableUnstableRenderSubtreeIntoContainer = false;
+
+export const warnUnstableRenderSubtreeIntoContainer = false;
+
+export const disableUnstableCreatePortal = false;
+
+export const isTestEnvironment = true;
+
+// Flow magic to verify the exports of this file match the original version.
+// eslint-disable-next-line no-unused-vars
+type Check<_X, Y: _X, X: Y = _X> = null;
+// eslint-disable-next-line no-unused-expressions
+(null: Check<FeatureFlagsShimType, FeatureFlagsType>);

packages/shared/forks/ReactFeatureFlags.www.js

@@ -7,6 +7,11 @@
  * @flow
  */
 
+/*
+  SYNC WITH forks/ReactFeatureFlags.testing.www.js
+  except isTestEnvironment = false
+*/
+
 import typeof * as FeatureFlagsType from 'shared/ReactFeatureFlags';
 import typeof * as FeatureFlagsShimType from './ReactFeatureFlags.www';