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Re-arrange main ReactFeatureFlags module
@sebmarkbage and I audited the feature flags file to review the status of each feature or experiment. Based on that, I've added some more comments to the main ReactFeatureFlags module and rearranged them into groups. I haven't changed the value of any flags, yet. There are a few we're going to land but I'll do them as separate PRs.
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‎packages/shared/ReactFeatureFlags.js‎

Lines changed: 182 additions & 121 deletions
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@@ -7,119 +7,102 @@
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* @flow strict
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*/
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10-
// Filter certain DOM attributes (e.g. src, href) if their values are empty strings.
11-
// This prevents e.g. <img src=""> from making an unnecessary HTTP request for certain browsers.
12-
export const enableFilterEmptyStringAttributesDOM = false;
13-
14-
// Adds verbose console logging for e.g. state updates, suspense, and work loop stuff.
15-
// Intended to enable React core members to more easily debug scheduling issues in DEV builds.
16-
export const enableDebugTracing = false;
17-
18-
// Adds user timing marks for e.g. state updates, suspense, and work loop stuff,
19-
// for an experimental timeline tool.
20-
export const enableSchedulingProfiler = __PROFILE__;
21-
22-
// Helps identify side effects in render-phase lifecycle hooks and setState
23-
// reducers by double invoking them in StrictLegacyMode.
24-
export const debugRenderPhaseSideEffectsForStrictMode = __DEV__;
25-
26-
// Helps identify code that is not safe for planned Offscreen API and Suspense semantics;
27-
// this feature flag only impacts StrictEffectsMode.
28-
export const enableStrictEffects = __DEV__;
29-
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// If TRUE, trees rendered with createRoot will be StrictEffectsMode.
31-
// If FALSE, these trees will be StrictLegacyMode.
32-
export const createRootStrictEffectsByDefault = false;
33-
34-
// To preserve the "Pause on caught exceptions" behavior of the debugger, we
35-
// replay the begin phase of a failed component inside invokeGuardedCallback.
36-
export const replayFailedUnitOfWorkWithInvokeGuardedCallback = __DEV__;
37-
38-
// Warn about deprecated, async-unsafe lifecycles; relates to RFC #6:
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export const warnAboutDeprecatedLifecycles = true;
40-
41-
// Gather advanced timing metrics for Profiler subtrees.
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export const enableProfilerTimer = __PROFILE__;
43-
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// Record durations for commit and passive effects phases.
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export const enableProfilerCommitHooks = __PROFILE__;
46-
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// Phase param passed to onRender callback differentiates between an "update" and a "cascading-update".
48-
export const enableProfilerNestedUpdatePhase = __PROFILE__;
49-
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// Profiler API accepts a function to be called when a nested update is scheduled.
51-
// This callback accepts the component type (class instance or function) the update is scheduled for.
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export const enableProfilerNestedUpdateScheduledHook = false;
53-
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// Track which Fiber(s) schedule render work.
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export const enableUpdaterTracking = __PROFILE__;
10+
// -----------------------------------------------------------------------------
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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
14+
// -----------------------------------------------------------------------------
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// SSR experiments
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export const warnOnSubscriptionInsideStartTransition = false;
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export const enableSuspenseServerRenderer = true;
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export const enableSelectiveHydration = true;
60-
61-
// Flight experiments
19+
export const warnAboutDeprecatedLifecycles = true;
6220
export const enableLazyElements = true;
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export const enableCache = __EXPERIMENTAL__;
21+
export const enableComponentStackLocations = true;
22+
export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
23+
export const warnUnstableRenderSubtreeIntoContainer = false;
24+
export const enablePersistentOffscreenHostContainer = false;
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65-
// Only used in www builds.
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export const enableSchedulerDebugging = false;
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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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// -----------------------------------------------------------------------------
32+
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// Destroy layout effects for components that are hidden because something
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// suspended in an update and recreate them when they are shown again (after the
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// suspended boundary has resolved). Note that this should be an uncommon use
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// case and can be avoided by using the transition API.
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//
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// TODO: Finish rolling out in www
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export const enableSuspenseLayoutEffectSemantics = true;
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68-
// Disable javascript: URL strings in href for XSS protection.
69-
export const disableJavaScriptURLs = false;
41+
// TODO: Finish rolling out in www
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export const enableClientRenderFallbackOnHydrationMismatch = true;
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71-
// Disable support for comment nodes as React DOM containers. Only supported
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// by www builds.
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export const disableCommentsAsDOMContainers = true;
44+
// TODO: Need to review this code one more time before landing
45+
export const enableCapturePhaseSelectiveHydrationWithoutDiscreteEventReplay = true;
7446

75-
// Experimental Scope support.
76-
export const enableScopeAPI = false;
47+
// Recoil still uses useMutableSource in www, need to delete
48+
export const enableUseMutableSource = false;
7749

78-
// Experimental Create Event Handle API.
79-
export const enableCreateEventHandleAPI = false;
50+
// Not sure if www still uses this. We don't have a replacement but whatever we
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// replace it with will likely be different than what's already there, so we
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// probably should just delete it as long as nothing in www relies on it.
53+
export const enableSchedulerDebugging = false;
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81-
// New API for JSX transforms to target - https://github.com/reactjs/rfcs/pull/107
55+
// Need to remove didTimeout argument from Scheduler before landing
56+
export const disableSchedulerTimeoutInWorkLoop = false;
8257

83-
// We will enforce mocking scheduler with scheduler/unstable_mock at some point. (v18?)
84-
// Till then, we warn about the missing mock, but still fallback to a legacy mode compatible version
58+
// -----------------------------------------------------------------------------
59+
// Slated for removal in the future (significant effort)
60+
//
61+
// 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.
63+
// -----------------------------------------------------------------------------
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8665
// Add a callback property to suspense to notify which promises are currently
8766
// in the update queue. This allows reporting and tracing of what is causing
8867
// the user to see a loading state.
68+
//
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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.
9173
export const enableSuspenseCallback = false;
9274

93-
// Part of the simplification of React.createElement so we can eventually move
94-
// from React.createElement to React.jsx
95-
// https://github.com/reactjs/rfcs/blob/createlement-rfc/text/0000-create-element-changes.md
96-
export const warnAboutDefaultPropsOnFunctionComponents = false;
97-
98-
export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
99-
100-
export const enableTrustedTypesIntegration = false;
101-
102-
// Enables a warning when trying to spread a 'key' to an element;
103-
// a deprecated pattern we want to get rid of in the future
104-
export const warnAboutSpreadingKeyToJSX = false;
75+
// Experimental Scope support.
76+
export const enableScopeAPI = false;
10577

106-
export const warnOnSubscriptionInsideStartTransition = false;
78+
// Experimental Create Event Handle API.
79+
export const enableCreateEventHandleAPI = false;
10780

108-
export const enableSuspenseAvoidThisFallback = false;
109-
export const enableSuspenseAvoidThisFallbackFizz = false;
81+
// This controls whether you get the `.old` modules or the `.new` modules in
82+
// the react-reconciler package.
83+
export const enableNewReconciler = false;
11084

111-
export const enableCapturePhaseSelectiveHydrationWithoutDiscreteEventReplay = true;
85+
// Support legacy Primer support on internal FB www
86+
export const enableLegacyFBSupport = false;
11287

113-
export const enableClientRenderFallbackOnHydrationMismatch = true;
88+
// -----------------------------------------------------------------------------
89+
// Ongoing experiments
90+
//
91+
// These are features that we're either actively exploring or are reasonably
92+
// likely to include in an upcoming release.
93+
// -----------------------------------------------------------------------------
11494

115-
export const enableComponentStackLocations = true;
95+
export const enableCache = __EXPERIMENTAL__;
11696

117-
export const enableNewReconciler = false;
97+
export const enableTransitionTracing = false;
11898

119-
export const disableNativeComponentFrames = false;
99+
// No known bugs, but needs performance testing
100+
export const enableLazyContextPropagation = false;
120101

121-
// Internal only.
122-
export const enableGetInspectorDataForInstanceInProduction = false;
102+
// Enables unstable_avoidThisFallback feature in Fiber
103+
export const enableSuspenseAvoidThisFallback = false;
104+
// Enables unstable_avoidThisFallback feature in Fizz
105+
export const enableSuspenseAvoidThisFallbackFizz = false;
123106

124107
// When a node is unmounted, recurse into the Fiber subtree and clean out
125108
// references. Each level cleans up more fiber fields than the previous level.
@@ -134,62 +117,140 @@ export const enableGetInspectorDataForInstanceInProduction = false;
134117
// aggressiveness.
135118
export const deletedTreeCleanUpLevel = 3;
136119

137-
// Destroy layout effects for components that are hidden because something suspended in an update
138-
// and recreate them when they are shown again (after the suspended boundary has resolved).
139-
// Note that this should be an uncommon use case and can be avoided by using the transition API.
140-
export const enableSuspenseLayoutEffectSemantics = true;
120+
// -----------------------------------------------------------------------------
121+
// Chopping Block
122+
//
123+
// Planned feature deprecations and breaking changes. Sorted roughly in order of
124+
// when we we plan to enable them.
125+
// -----------------------------------------------------------------------------
126+
127+
// This flag enables Strict Effects by default. We're not turning this on until
128+
// after 18 because it requires migration work. Recommendation is to use
129+
// <StrictMode /> to gradually upgrade components.
130+
// If TRUE, trees rendered with createRoot will be StrictEffectsMode.
131+
// If FALSE, these trees will be StrictLegacyMode.
132+
export const createRootStrictEffectsByDefault = false;
133+
134+
export const disableModulePatternComponents = false;
135+
136+
export const disableLegacyContext = false;
137+
138+
export const enableUseRefAccessWarning = false;
139+
140+
// Enables time slicing for updates that aren't wrapped in startTransition.
141+
export const enableSyncDefaultUpdates = true;
142+
143+
// Adds an opt-in to time slicing for updates that aren't wrapped in
144+
// startTransition. Only relevant when enableSyncDefaultUpdates is disabled.
145+
export const allowConcurrentByDefault = false;
146+
147+
// Updates that occur in the render phase are not officially supported. But when
148+
// they do occur, we defer them to a subsequent render by picking a lane that's
149+
// not currently rendering. We treat them the same as if they came from an
150+
// interleaved event. Remove this flag once we have migrated to the
151+
// new behavior.
152+
// NOTE: Not sure if we'll end up doing this or not.
153+
export const deferRenderPhaseUpdateToNextBatch = false;
154+
155+
// -----------------------------------------------------------------------------
156+
// React DOM Chopping Block
157+
//
158+
// Similar to main Chopping Block but only flags related to React DOM. These are
159+
// grouped because we will likely batch all of them into a single major release.
160+
// -----------------------------------------------------------------------------
161+
162+
// Disable support for comment nodes as React DOM containers. Already disabled
163+
// in open source, but www codebase still relies on it. Need to remove.
164+
export const disableCommentsAsDOMContainers = true;
165+
166+
// Disable javascript: URL strings in href for XSS protection.
167+
export const disableJavaScriptURLs = false;
168+
169+
export const enableTrustedTypesIntegration = false;
170+
171+
// Prevent the value and checked attributes from syncing with their related
172+
// DOM properties
173+
export const disableInputAttributeSyncing = false;
174+
175+
// Filter certain DOM attributes (e.g. src, href) if their values are empty
176+
// strings. This prevents e.g. <img src=""> from making an unnecessary HTTP
177+
// request for certain browsers.
178+
export const enableFilterEmptyStringAttributesDOM = false;
141179

142180
// Changes the behavior for rendering custom elements in both server rendering
143181
// and client rendering, mostly to allow JSX attributes to apply to the custom
144182
// element's object properties instead of only HTML attributes.
145183
// https://github.com/facebook/react/issues/11347
146184
export const enableCustomElementPropertySupport = __EXPERIMENTAL__;
147185

148-
// --------------------------
149-
// Future APIs to be deprecated
150-
// --------------------------
186+
// Disables children for <textarea> elements
187+
export const disableTextareaChildren = false;
151188

152-
// Prevent the value and checked attributes from syncing
153-
// with their related DOM properties
154-
export const disableInputAttributeSyncing = false;
189+
// -----------------------------------------------------------------------------
190+
// JSX Chopping Block
191+
//
192+
// Similar to main Chopping Block but only flags related to JSX. These are
193+
// grouped because we will likely batch all of them into a single major release.
194+
// -----------------------------------------------------------------------------
155195

156-
export const warnAboutStringRefs = false;
196+
// New API for JSX transforms to target - https://github.com/reactjs/rfcs/pull/107
157197

158-
export const disableLegacyContext = false;
198+
// Part of the simplification of React.createElement so we can eventually move
199+
// from React.createElement to React.jsx
200+
// https://github.com/reactjs/rfcs/blob/createlement-rfc/text/0000-create-element-changes.md
201+
export const warnAboutDefaultPropsOnFunctionComponents = false; // deprecate later, not 18.0
159202

160-
// Disables children for <textarea> elements
161-
export const disableTextareaChildren = false;
203+
// Enables a warning when trying to spread a 'key' to an element;
204+
// a deprecated pattern we want to get rid of in the future
205+
export const warnAboutSpreadingKeyToJSX = false;
162206

163-
export const disableModulePatternComponents = false;
207+
export const warnAboutStringRefs = false;
164208

165-
// We should remove this flag once the above flag becomes enabled
166-
export const warnUnstableRenderSubtreeIntoContainer = false;
209+
// -----------------------------------------------------------------------------
210+
// Debugging and DevTools
211+
// -----------------------------------------------------------------------------
167212

168-
// Support legacy Primer support on internal FB www
169-
export const enableLegacyFBSupport = false;
213+
// Adds user timing marks for e.g. state updates, suspense, and work loop stuff,
214+
// for an experimental timeline tool.
215+
export const enableSchedulingProfiler = __PROFILE__;
170216

171-
// Updates that occur in the render phase are not officially supported. But when
172-
// they do occur, we defer them to a subsequent render by picking a lane that's
173-
// not currently rendering. We treat them the same as if they came from an
174-
// interleaved event. Remove this flag once we have migrated to the
175-
// new behavior.
176-
export const deferRenderPhaseUpdateToNextBatch = false;
217+
// Helps identify side effects in render-phase lifecycle hooks and setState
218+
// reducers by double invoking them in StrictLegacyMode.
219+
export const debugRenderPhaseSideEffectsForStrictMode = __DEV__;
177220

178-
export const enableUseRefAccessWarning = false;
221+
// Helps identify code that is not safe for planned Offscreen API and Suspense semantics;
222+
// this feature flag only impacts StrictEffectsMode.
223+
export const enableStrictEffects = __DEV__;
179224

180-
export const disableSchedulerTimeoutInWorkLoop = false;
225+
// To preserve the "Pause on caught exceptions" behavior of the debugger, we
226+
// replay the begin phase of a failed component inside invokeGuardedCallback.
227+
export const replayFailedUnitOfWorkWithInvokeGuardedCallback = __DEV__;
181228

182-
export const enableLazyContextPropagation = false;
229+
// Gather advanced timing metrics for Profiler subtrees.
230+
export const enableProfilerTimer = __PROFILE__;
183231

184-
export const enableSyncDefaultUpdates = true;
232+
// Record durations for commit and passive effects phases.
233+
export const enableProfilerCommitHooks = __PROFILE__;
185234

186-
export const allowConcurrentByDefault = false;
235+
// Phase param passed to onRender callback differentiates between an "update" and a "cascading-update".
236+
export const enableProfilerNestedUpdatePhase = __PROFILE__;
187237

188-
export const enablePersistentOffscreenHostContainer = false;
238+
// Adds verbose console logging for e.g. state updates, suspense, and work loop
239+
// stuff. Intended to enable React core members to more easily debug scheduling
240+
// issues in DEV builds.
241+
export const enableDebugTracing = false;
189242

190-
export const consoleManagedByDevToolsDuringStrictMode = true;
243+
// Track which Fiber(s) schedule render work.
244+
export const enableUpdaterTracking = __PROFILE__;
191245

192-
// Only enabled in www builds
193-
export const enableUseMutableSource = false;
246+
// Only enabled in RN, related to enableComponentStackLocations
247+
export const disableNativeComponentFrames = false;
194248

195-
export const enableTransitionTracing = false;
249+
// Internal only.
250+
export const enableGetInspectorDataForInstanceInProduction = false;
251+
252+
// Profiler API accepts a function to be called when a nested update is scheduled.
253+
// This callback accepts the component type (class instance or function) the update is scheduled for.
254+
export const enableProfilerNestedUpdateScheduledHook = false;
255+
256+
export const consoleManagedByDevToolsDuringStrictMode = true;

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