unify feature flags between fb and oss for React Native renderer

[sammy-SC]

Affected flags:

alwaysThrottleRetries

In RN OSS changed from true to false. This is what FB build uses. This flag was a root cause for big perf regression internally.

enableDeferRootSchedulingToMicrotask

In RN OSS build changed from true to false. This is what FB build uses.

debugRenderPhaseSideEffectsForStrictMode

Changed from true to DEV in FB and OSS build. The flag is only used in debug builds and was previously false in RN OSS builds

enableUnifiedSyncLane

Changed from __VARIANT__ to true in FB build. This is what OSS build uses. This flag is shipped internally. cc @tyao1

enableLegacyHidden

In RN FB changed from true to false. This is what OSS uses.

allowConcurrentByDefault

In RN FB changed from true to false.

I ran yarn flags --diff rn rn-fb to get the difference between feature flags and unify them.

Before

yarn run v1.22.19
$ node ./scripts/flags/flags.js --diff rn rn-fb
┌───────────────────────────────────────────────┬────────┬───────┐
│                    (index)                    │ RN OSS │ RN FB │
├───────────────────────────────────────────────┼────────┼───────┤
│ allowConcurrentByDefault                      │  '❌'  │ '✅'  │
│ debugRenderPhaseSideEffectsForStrictMode      │  '❌'  │ '✅'  │
│ disableModulePatternComponents                │  '❌'  │ '✅'  │
│ enableCPUSuspense                             │  '❌'  │ '✅'  │
│ enableCacheElement                            │  '❌'  │ '✅'  │
│ enableGetInspectorDataForInstanceInProduction │  '❌'  │ '✅'  │
│ enableLegacyHidden                            │  '❌'  │ '✅'  │
│ enableSchedulingProfiler                      │  '❌'  │ '📊'  │
│ enableUseDeferredValueInitialArg              │  '❌'  │ '✅'  │
│ enableUseMemoCacheHook                        │  '❌'  │ '✅'  │
│ enableUseRefAccessWarning                     │  '❌'  │ '🧪'  │
│ passChildrenWhenCloningPersistedNodes         │  '❌'  │ '🧪'  │
│ useMicrotasksForSchedulingInFabric            │  '❌'  │ '🧪'  │
│ alwaysThrottleRetries                         │  '✅'  │ '🧪'  │
│ enableDeferRootSchedulingToMicrotask          │  '✅'  │ '🧪'  │
│ enableUnifiedSyncLane                         │  '✅'  │ '🧪'  │
└───────────────────────────────────────────────┴────────┴───────┘

After

yarn run v1.22.19
$ node ./scripts/flags/flags.js --diff rn rn-fb
┌───────────────────────────────────────────────┬────────┬───────┐
│                    (index)                    │ RN OSS │ RN FB │
├───────────────────────────────────────────────┼────────┼───────┤
│ alwaysThrottleRetries                         │  '❌'  │ '🧪'  │
│ disableModulePatternComponents                │  '❌'  │ '✅'  │
│ enableCPUSuspense                             │  '❌'  │ '✅'  │
│ enableCacheElement                            │  '❌'  │ '✅'  │
│ enableDeferRootSchedulingToMicrotask          │  '❌'  │ '🧪'  │
│ enableGetInspectorDataForInstanceInProduction │  '❌'  │ '✅'  │
│ enableSchedulingProfiler                      │  '❌'  │ '📊'  │
│ enableUseDeferredValueInitialArg              │  '❌'  │ '✅'  │
│ enableUseMemoCacheHook                        │  '❌'  │ '✅'  │
│ enableUseRefAccessWarning                     │  '❌'  │ '🧪'  │
│ passChildrenWhenCloningPersistedNodes         │  '❌'  │ '🧪'  │
│ useMicrotasksForSchedulingInFabric            │  '❌'  │ '🧪'  │
└───────────────────────────────────────────────┴────────┴───────┘

[react-sizebot]

Comparing: bfdc12c...329f58d

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
oss-stable/react-dom/cjs/react-dom.production.min.js	=	176.66 kB	176.66 kB	=	55.01 kB	55.01 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	178.65 kB	178.65 kB	=	55.59 kB	55.59 kB
facebook-www/ReactDOM-prod.classic.js	=	591.78 kB	591.78 kB	=	104.44 kB	104.44 kB
facebook-www/ReactDOM-prod.modern.js	=	575.53 kB	575.53 kB	=	101.54 kB	101.54 kB
facebook-react-native/react-is/cjs/ReactIs-prod.js	=	4.73 kB	4.63 kB	=	1.18 kB	1.15 kB
facebook-react-native/react-is/cjs/ReactIs-profiling.js	=	4.73 kB	4.63 kB	=	1.18 kB	1.15 kB
test_utils/ReactAllWarnings.js	Deleted	67.02 kB	0.00 kB	Deleted	16.42 kB	0.00 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
react-native/implementations/ReactFabric-dev.js	+0.28%	981.18 kB	983.90 kB	+0.17%	198.37 kB	198.70 kB
react-native/implementations/ReactNativeRenderer-dev.js	+0.27%	997.46 kB	1,000.18 kB	+0.17%	202.66 kB	203.00 kB
react-native/implementations/ReactNativeRenderer-dev.fb.js	=	1,022.86 kB	1,020.29 kB	=	206.67 kB	206.25 kB
react-native/implementations/ReactFabric-dev.fb.js	=	1,008.26 kB	1,005.68 kB	=	202.84 kB	202.39 kB
react-native/implementations/ReactNativeRenderer-profiling.fb.js	=	364.42 kB	362.67 kB	=	64.04 kB	63.72 kB
react-native/implementations/ReactFabric-profiling.fb.js	=	356.89 kB	355.14 kB	=	62.62 kB	62.32 kB
react-native/implementations/ReactNativeRenderer-prod.fb.js	=	337.17 kB	335.42 kB	=	59.80 kB	59.47 kB
react-native/implementations/ReactFabric-prod.fb.js	=	329.65 kB	327.90 kB	=	58.43 kB	58.11 kB
facebook-react-native/react-is/cjs/ReactIs-dev.js	=	7.98 kB	7.93 kB	=	1.98 kB	1.97 kB
facebook-react-native/react-is/cjs/ReactIs-prod.js	=	4.73 kB	4.63 kB	=	1.18 kB	1.15 kB
facebook-react-native/react-is/cjs/ReactIs-profiling.js	=	4.73 kB	4.63 kB	=	1.18 kB	1.15 kB
test_utils/ReactAllWarnings.js	Deleted	67.02 kB	0.00 kB	Deleted	16.42 kB	0.00 kB

Generated by 🚫 dangerJS against 329f58d

[rickhanlonii]

The right fix for these depends on the flag.

These are good:

• enableUnifiedSyncLane
• debugRenderPhaseSideEffectsForStrictMode

These need to land at FB

The right fix for these to to land them at FB, not change them in OSS.

• allowConcurrentByDefault: RN OSS shouldn't use concurrent by default. This is only on in RN FB because landing it breaks relay tests. We should fix the relay tests and turn this off at FB.
• alwaysThrottleRetries - do we have a plan to land this? What was the regression and was it FB specific? RN OSS isn't using suspense so I think we should leave this on.
• enableDeferRootSchedulingToMicrotask - we should land this at FB and keep the OSS one on.

These are experimental, should stay enabled in Fb build

These are experimental and should stay on in the FB builds so we can catch any unintentional regressions. If the changes are limited to only when the API is used, then keeping this on internally is harmless. But if there are, and we miss them, turning it on later could be difficult

• enableCPUSuspense
• enableCacheElement

Can't turn on 19 features

These are 19 features that will break paper, so we need to decide what to do here. Turning it off at FB doesn't seem like the right move, since FB is on 19 already. We should roll the feature out to RN OSS in 19:

• disableModulePatternComponents
• enableUseDeferredValueInitialArg

Not sure about these

• enableLegacyHidden: what does this do? Is it a breaking change to turn it off?
• enableUseMemoCacheHook: we have not decided whether we're including this in the 19 release in OSS yet. It's only experimental in React, so we shouldn't ship it to RN OSS yet.

[rickhanlonii]

Awesome, thanks for doing this!