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This flag first moves the `shouldYield()` logic into React itself. We need this for `postTask` compatibility anyway since this logic is no longer a concern of the scheduler. This means that there can also be no global `requestPaint()` that asks for painting earlier. So this is best rolled out with `enableAlwaysYieldScheduler` (and ideally `enableYieldingBeforePassive`) instead of `enableRequestPaint`. Once in React we can change the yield timing heuristics. This uses the previous 5ms for Idle work to keep everything responsive while doing background work. However, for Transitions and Retries we have seen that same thread animations (like loading states animating, or constant animations like cool Three.js stuff) can take CPU time away from the Transition that causes moving into new content to slow down. Therefore we only yield every 25ms. The purpose of this yield is not to avoid the overhead of yielding, which is very low, but rather to intentionally block any frequently occurring other main thread work like animations from starving our work. If we could we could just tell everyone else to throttle their stuff for ideal scheduling but that's not quite realistic. In other words, the purpose of this is to reduce the frame rate of animations to 30 fps and we achieve this by not yielding. We still do yield to allow the animations to not just stall. This seems like a good balance. The 5ms of Idle is because we don't really need to yield less often since the overhead is low. We keep it low to allow 120 fps animations to run if necessary and our work may not be the only work within a frame so we need to yield early enough to leave enough time left. Similarly we choose 25ms rather than say 35ms to ensure that we push long enough to guarantee to half the frame rate but low enough that there's plenty of time left for a rAF to power each animation every other frame. It's also low enough that if something else interrupts the work like a new interaction, we can still be responsive to that within 50ms or so. We also need to yield in case there's I/O work that needs to get bounced through the main thread. This flag is currently off everywhere since we have so many other scheduling flags but that means there's some urgency to roll those out fully so we can test this one. There's also some tests to update since this doesn't go through the Mock scheduler anymore for yields.
270 lines
9.8 KiB
JavaScript
270 lines
9.8 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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// None
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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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export const enableHydrationLaneScheduling = true;
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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 favorSafetyOverHydrationPerf = 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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// TODO: Land at Meta before removing.
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export const disableDefaultPropsExceptForClasses = 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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// Yield to the browser event loop and not just the scheduler event loop before passive effects.
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// Fix gated tests that fail with this flag enabled before turning it back on.
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export const enableYieldingBeforePassive = false;
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// Experiment to intentionally yield less to block high framerate animations.
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export const enableThrottledScheduling = false;
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export const enableLegacyCache = __EXPERIMENTAL__;
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export const enableAsyncIterableChildren = __EXPERIMENTAL__;
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export const enableTaint = __EXPERIMENTAL__;
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export const enablePostpone = __EXPERIMENTAL__;
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export const enableHalt = __EXPERIMENTAL__;
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/**
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* Switches the Fabric API from doing layout in commit work instead of complete work.
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*/
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export const enableFabricCompleteRootInCommitPhase = false;
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/**
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* Switches Fiber creation to a simple object instead of a constructor.
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*/
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export const enableObjectFiber = false;
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export const enableTransitionTracing = 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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export const enableCPUSuspense = __EXPERIMENTAL__;
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// Test this at Meta before enabling.
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export const enableNoCloningMemoCache = false;
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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 = __EXPERIMENTAL__;
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export const alwaysThrottleRetries = true;
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export const passChildrenWhenCloningPersistedNodes = false;
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export const enableServerComponentLogs = true;
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/**
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* Enables a new Fiber flag used in persisted mode to reduce the number
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* of cloned host components.
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*/
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export const enablePersistedModeClonedFlag = false;
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export const enableOwnerStacks = __EXPERIMENTAL__;
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export const enableShallowPropDiffing = false;
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export const enableSiblingPrerendering = true;
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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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* 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 = false;
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/**
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* Experimental new hook for better managing resources in effects.
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*/
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export const enableUseResourceEffectHook = false;
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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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// TODO: Anything that's set to `true` in this section should either be cleaned
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// up (if it's on everywhere, including Meta and RN builds) or moved to a
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// different section of this file.
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// const __NEXT_MAJOR__ = __EXPERIMENTAL__;
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// Renames the internal symbol for elements since they have changed signature/constructor
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export const renameElementSymbol = true;
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/**
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* Enables a fix to run insertion effect cleanup on hidden subtrees.
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*/
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export const enableHiddenSubtreeInsertionEffectCleanup = false;
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/**
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* Removes legacy style context defined using static `contextTypes` and consumed with static `childContextTypes`.
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*/
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export const disableLegacyContext = true;
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/**
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* Removes legacy style context just from function components.
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*/
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export const disableLegacyContextForFunctionComponents = true;
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// Enable the moveBefore() alternative to insertBefore(). This preserves states of moves.
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export const enableMoveBefore = false;
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// Disabled caching behavior of `react/cache` in client runtimes.
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export const disableClientCache = true;
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// Warn on any usage of ReactTestRenderer
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export const enableReactTestRendererWarning = true;
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// Disables legacy mode
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// This allows us to land breaking changes to remove legacy mode APIs in experimental builds
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// before removing them in stable in the next Major
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export const disableLegacyMode = true;
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// Make <Context> equivalent to <Context.Provider> instead of <Context.Consumer>
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export const enableRenderableContext = 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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// -----------------------------------------------------------------------------
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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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// Gather advanced timing metrics for Profiler subtrees.
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export const enableProfilerTimer = __PROFILE__;
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// Adds performance.measure() marks using Chrome extensions to allow formatted
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// Component rendering tracks to show up in the Performance tab.
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// This flag will be used for both Server Component and Client Component tracks.
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// All calls should also be gated on enableProfilerTimer.
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export const enableComponentPerformanceTrack = __EXPERIMENTAL__;
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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: boolean =
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!enableComponentPerformanceTrack && __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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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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export const enableDO_NOT_USE_disableStrictPassiveEffect = false;
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