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7e87df8090
We'll use this in www to test whether the polyfill is better at scheduling high-pri async work than the native one. My preliminary tests suggest "yes" but it's hard to say for certain, given how difficult it is to consistently reproduce the starvation issues we've been seeing.
71 lines
2.2 KiB
JavaScript
71 lines
2.2 KiB
JavaScript
/**
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* Copyright (c) 2013-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @flow
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*/
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import typeof * as FeatureFlagsType from 'shared/ReactFeatureFlags';
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import typeof * as FeatureFlagsShimType from './ReactFeatureFlags.www';
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// Re-export dynamic flags from the www version.
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export const {
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enableGetDerivedStateFromCatch,
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debugRenderPhaseSideEffects,
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debugRenderPhaseSideEffectsForStrictMode,
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warnAboutDeprecatedLifecycles,
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replayFailedUnitOfWorkWithInvokeGuardedCallback,
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alwaysUseRequestIdleCallbackPolyfill,
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} = require('ReactFeatureFlags');
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// The rest of the flags are static for better dead code elimination.
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export const enableCreateRoot = true;
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// The www bundles only use the mutating reconciler.
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export const enableMutatingReconciler = true;
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export const enableNoopReconciler = false;
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export const enablePersistentReconciler = false;
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// In www, we have experimental support for gathering data
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// from User Timing API calls in production. By default, we
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// only emit performance.mark/measure calls in __DEV__. But if
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// somebody calls addUserTimingListener() which is exposed as an
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// experimental FB-only export, we call performance.mark/measure
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// as long as there is more than a single listener.
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export let enableUserTimingAPI = __DEV__;
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let refCount = 0;
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export function addUserTimingListener() {
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if (__DEV__) {
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// Noop.
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return () => {};
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}
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refCount++;
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updateFlagOutsideOfReactCallStack();
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return () => {
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refCount--;
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updateFlagOutsideOfReactCallStack();
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};
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}
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// The flag is intentionally updated in a timeout.
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// We don't support toggling it during reconciliation or
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// commit since that would cause mismatching user timing API calls.
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let timeout = null;
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function updateFlagOutsideOfReactCallStack() {
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if (!timeout) {
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timeout = setTimeout(() => {
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timeout = null;
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enableUserTimingAPI = refCount > 0;
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});
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}
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}
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// Flow magic to verify the exports of this file match the original version.
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// eslint-disable-next-line no-unused-vars
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type Check<_X, Y: _X, X: Y = _X> = null;
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// eslint-disable-next-line no-unused-expressions
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(null: Check<FeatureFlagsShimType, FeatureFlagsType>);
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