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14fd9630ee
Previously, `<Context>` was equivalent to `<Context.Consumer>`. However,
since the introduction of Hooks, the `<Context.Consumer>` API is rarely
used. The goal here is to make the common case cleaner:
```js
const ThemeContext = createContext('light')
function App() {
return (
<ThemeContext value="dark">
...
</ThemeContext>
)
}
function Button() {
const theme = use(ThemeContext)
// ...
}
```
This is technically a breaking change, but we've been warning about
rendering `<Context>` directly for several years by now, so it's
unlikely much code in the wild depends on the old behavior. [Proof that
it warns today (check
console).](https://codesandbox.io/p/sandbox/peaceful-nobel-pdxtfl)
---
**The relevant commit is 5696782b428a5ace96e66c1857e13249b6c07958.** It
switches `createContext` implementation so that `Context.Provider ===
Context`.
The main assumption that changed is that a Provider's fiber type is now
the context itself (rather than an intermediate object). Whereas a
Consumer's fiber type is now always an intermediate object (rather than
it being sometimes the context itself and sometimes an intermediate
object).
My methodology was to start with the relevant symbols, work tags, and
types, and work my way backwards to all usages.
This might break tooling that depends on inspecting React's internal
fields. I've added DevTools support in the second commit. This didn't
need explicit versioning—the structure tells us enough.
265 lines
10 KiB
JavaScript
265 lines
10 KiB
JavaScript
/**
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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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 strict
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*/
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// -----------------------------------------------------------------------------
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// Land or remove (zero effort)
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//
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// Flags that can likely be deleted or landed without consequences
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// -----------------------------------------------------------------------------
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export const enableComponentStackLocations = true;
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// -----------------------------------------------------------------------------
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// Killswitch
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//
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// Flags that exist solely to turn off a change in case it causes a regression
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// when it rolls out to prod. We should remove these as soon as possible.
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// -----------------------------------------------------------------------------
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// -----------------------------------------------------------------------------
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// Land or remove (moderate effort)
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//
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// Flags that can be probably deleted or landed, but might require extra effort
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// like migrating internal callers or performance testing.
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// -----------------------------------------------------------------------------
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// TODO: Finish rolling out in www
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export const enableClientRenderFallbackOnTextMismatch = true;
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export const enableFormActions = true;
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export const enableAsyncActions = true;
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// Need to remove didTimeout argument from Scheduler before landing
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export const disableSchedulerTimeoutInWorkLoop = false;
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// This will break some internal tests at Meta so we need to gate this until
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// those can be fixed.
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export const enableDeferRootSchedulingToMicrotask = true;
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// -----------------------------------------------------------------------------
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// Slated for removal in the future (significant effort)
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//
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// These are experiments that didn't work out, and never shipped, but we can't
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// delete from the codebase until we migrate internal callers.
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// -----------------------------------------------------------------------------
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// Add a callback property to suspense to notify which promises are currently
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// in the update queue. This allows reporting and tracing of what is causing
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// the user to see a loading state.
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//
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// Also allows hydration callbacks to fire when a dehydrated boundary gets
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// hydrated or deleted.
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//
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// This will eventually be replaced by the Transition Tracing proposal.
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export const enableSuspenseCallback = false;
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// Experimental Scope support.
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export const enableScopeAPI = false;
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// Experimental Create Event Handle API.
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export const enableCreateEventHandleAPI = false;
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// Support legacy Primer support on internal FB www
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export const enableLegacyFBSupport = false;
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// -----------------------------------------------------------------------------
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// Ongoing experiments
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//
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// These are features that we're either actively exploring or are reasonably
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// likely to include in an upcoming release.
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// -----------------------------------------------------------------------------
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export const enableCache = true;
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export const enableLegacyCache = __EXPERIMENTAL__;
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export const enableCacheElement = __EXPERIMENTAL__;
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export const enableFetchInstrumentation = true;
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export const enableBinaryFlight = __EXPERIMENTAL__;
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export const enableTaint = __EXPERIMENTAL__;
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export const enablePostpone = __EXPERIMENTAL__;
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export const enableTransitionTracing = false;
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// No known bugs, but needs performance testing
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export const enableLazyContextPropagation = false;
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// FB-only usage. The new API has different semantics.
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export const enableLegacyHidden = false;
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// Enables unstable_avoidThisFallback feature in Fiber
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export const enableSuspenseAvoidThisFallback = false;
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// Enables unstable_avoidThisFallback feature in Fizz
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export const enableSuspenseAvoidThisFallbackFizz = false;
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export const enableCPUSuspense = __EXPERIMENTAL__;
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export const enableFloat = true;
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// Enables unstable_useMemoCache hook, intended as a compilation target for
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// auto-memoization.
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export const enableUseMemoCacheHook = __EXPERIMENTAL__;
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export const enableUseEffectEventHook = __EXPERIMENTAL__;
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// Test in www before enabling in open source.
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// Enables DOM-server to stream its instruction set as data-attributes
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// (handled with an MutationObserver) instead of inline-scripts
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export const enableFizzExternalRuntime = true;
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export const alwaysThrottleRetries = true;
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export const useMicrotasksForSchedulingInFabric = false;
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export const passChildrenWhenCloningPersistedNodes = false;
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export const enableUseDeferredValueInitialArg = __EXPERIMENTAL__;
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export const enableRenderableContext = false;
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/**
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* Enables an expiration time for retry lanes to avoid starvation.
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*/
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export const enableRetryLaneExpiration = false;
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export const retryLaneExpirationMs = 5000;
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export const syncLaneExpirationMs = 250;
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export const transitionLaneExpirationMs = 5000;
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// -----------------------------------------------------------------------------
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// Ready for next major.
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//
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// Alias __NEXT_MAJOR__ to __EXPERIMENTAL__ for easier skimming.
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// -----------------------------------------------------------------------------
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const __NEXT_MAJOR__ = __EXPERIMENTAL__;
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// Not ready to break experimental yet.
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export const disableLegacyContext = false;
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// Not ready to break experimental yet.
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// Disable javascript: URL strings in href for XSS protection.
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export const disableJavaScriptURLs = false;
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// Not ready to break experimental yet.
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// Modern <StrictMode /> behaviour aligns more with what components
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// components will encounter in production, especially when used With <Offscreen />.
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// TODO: clean up legacy <StrictMode /> once tests pass WWW.
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export const useModernStrictMode = __NEXT_MAJOR__;
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// Not ready to break experimental yet.
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// Remove IE and MsApp specific workarounds for innerHTML
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export const disableIEWorkarounds = __NEXT_MAJOR__;
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// Changes the behavior for rendering custom elements in both server rendering
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// and client rendering, mostly to allow JSX attributes to apply to the custom
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// element's object properties instead of only HTML attributes.
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// https://github.com/facebook/react/issues/11347
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export const enableCustomElementPropertySupport = __NEXT_MAJOR__;
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// Filter certain DOM attributes (e.g. src, href) if their values are empty
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// strings. This prevents e.g. <img src=""> from making an unnecessary HTTP
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// request for certain browsers.
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export const enableFilterEmptyStringAttributesDOM = __NEXT_MAJOR__;
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// Disabled caching behavior of `react/cache` in client runtimes.
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export const disableClientCache = false;
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// Changes Server Components Reconciliation when they have keys
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export const enableServerComponentKeys = __NEXT_MAJOR__;
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/**
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* Enables a new error detection for infinite render loops from updates caused
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* by setState or similar outside of the component owning the state.
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*/
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export const enableInfiniteRenderLoopDetection = true;
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// -----------------------------------------------------------------------------
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// Chopping Block
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//
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// Planned feature deprecations and breaking changes. Sorted roughly in order of
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// when we plan to enable them.
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// -----------------------------------------------------------------------------
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export const disableModulePatternComponents = false;
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export const enableUseRefAccessWarning = false;
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// Enables time slicing for updates that aren't wrapped in startTransition.
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export const forceConcurrentByDefaultForTesting = false;
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export const enableUnifiedSyncLane = true;
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// Adds an opt-in to time slicing for updates that aren't wrapped in startTransition.
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export const allowConcurrentByDefault = false;
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// -----------------------------------------------------------------------------
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// React DOM Chopping Block
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//
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// Similar to main Chopping Block but only flags related to React DOM. These are
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// grouped because we will likely batch all of them into a single major release.
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// -----------------------------------------------------------------------------
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// Disable support for comment nodes as React DOM containers. Already disabled
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// in open source, but www codebase still relies on it. Need to remove.
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export const disableCommentsAsDOMContainers = true;
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export const enableTrustedTypesIntegration = false;
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// Prevent the value and checked attributes from syncing with their related
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// DOM properties
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export const disableInputAttributeSyncing = false;
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// Disables children for <textarea> elements
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export const disableTextareaChildren = false;
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// -----------------------------------------------------------------------------
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// Debugging and DevTools
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// -----------------------------------------------------------------------------
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// Adds user timing marks for e.g. state updates, suspense, and work loop stuff,
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// for an experimental timeline tool.
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export const enableSchedulingProfiler = __PROFILE__;
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// Helps identify side effects in render-phase lifecycle hooks and setState
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// reducers by double invoking them in StrictLegacyMode.
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export const debugRenderPhaseSideEffectsForStrictMode = __DEV__;
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// To preserve the "Pause on caught exceptions" behavior of the debugger, we
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// replay the begin phase of a failed component inside invokeGuardedCallback.
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export const replayFailedUnitOfWorkWithInvokeGuardedCallback = __DEV__;
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// Gather advanced timing metrics for Profiler subtrees.
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export const enableProfilerTimer = __PROFILE__;
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// Record durations for commit and passive effects phases.
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export const enableProfilerCommitHooks = __PROFILE__;
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// Phase param passed to onRender callback differentiates between an "update" and a "cascading-update".
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export const enableProfilerNestedUpdatePhase = __PROFILE__;
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// Adds verbose console logging for e.g. state updates, suspense, and work loop
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// stuff. Intended to enable React core members to more easily debug scheduling
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// issues in DEV builds.
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export const enableDebugTracing = false;
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export const enableAsyncDebugInfo = __EXPERIMENTAL__;
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// Track which Fiber(s) schedule render work.
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export const enableUpdaterTracking = __PROFILE__;
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// Internal only.
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export const enableGetInspectorDataForInstanceInProduction = false;
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// Profiler API accepts a function to be called when a nested update is scheduled.
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// This callback accepts the component type (class instance or function) the update is scheduled for.
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export const enableProfilerNestedUpdateScheduledHook = false;
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export const consoleManagedByDevToolsDuringStrictMode = true;
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export const enableDO_NOT_USE_disableStrictPassiveEffect = false;
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