[RN] Use microtasks in the RN renderer based on a global flag defined by RN

.eslintrc.js

@@ -427,6 +427,7 @@ module.exports = {
       files: ['packages/react-native-renderer/**/*.js'],
       globals: {
         nativeFabricUIManager: 'readonly',
+        RN$enableMicrotasksInReact: 'readonly',
       },
     },
     {

packages/react-native-renderer/src/ReactFiberConfigFabric.js

@@ -47,10 +47,7 @@ const {
   unstable_getCurrentEventPriority: fabricGetCurrentEventPriority,
 } = nativeFabricUIManager;
 
-import {
-  useMicrotasksForSchedulingInFabric,
-  passChildrenWhenCloningPersistedNodes,
-} from 'shared/ReactFeatureFlags';
+import {passChildrenWhenCloningPersistedNodes} from 'shared/ReactFeatureFlags';
 
 const {get: getViewConfigForType} = ReactNativeViewConfigRegistry;
 
@@ -507,6 +504,10 @@ export const NotPendingTransition: TransitionStatus = null;
 // -------------------
 //     Microtasks
 // -------------------
-export const supportsMicrotasks = useMicrotasksForSchedulingInFabric;
+
+export const supportsMicrotasks: boolean =
+  typeof RN$enableMicrotasksInReact !== 'undefined' &&
+  !!RN$enableMicrotasksInReact;
+
 export const scheduleMicrotask: any =
   typeof queueMicrotask === 'function' ? queueMicrotask : scheduleTimeout;

packages/shared/ReactFeatureFlags.js

@@ -115,8 +115,6 @@ export const enableFizzExternalRuntime = true;
 
 export const alwaysThrottleRetries = true;
 
-export const useMicrotasksForSchedulingInFabric = false;
-
 export const passChildrenWhenCloningPersistedNodes = false;
 
 export const enableUseDeferredValueInitialArg = __EXPERIMENTAL__;

packages/shared/forks/ReactFeatureFlags.native-fb-dynamic.js

@@ -30,7 +30,6 @@ export const enableRenderableContext = __VARIANT__;
 export const enableUnifiedSyncLane = __VARIANT__;
 export const enableUseRefAccessWarning = __VARIANT__;
 export const passChildrenWhenCloningPersistedNodes = __VARIANT__;
-export const useMicrotasksForSchedulingInFabric = __VARIANT__;
 export const useModernStrictMode = __VARIANT__;
 
 // Flow magic to verify the exports of this file match the original version.

packages/shared/forks/ReactFeatureFlags.native-fb.js

@@ -28,7 +28,6 @@ export const {
   enableUnifiedSyncLane,
   enableUseRefAccessWarning,
   passChildrenWhenCloningPersistedNodes,
-  useMicrotasksForSchedulingInFabric,
   useModernStrictMode,
 } = dynamicFlags;
 

packages/shared/forks/ReactFeatureFlags.native-oss.js

@@ -82,7 +82,6 @@ export const enableAsyncActions = false;
 
 export const alwaysThrottleRetries = false;
 
-export const useMicrotasksForSchedulingInFabric = false;
 export const passChildrenWhenCloningPersistedNodes = false;
 export const enableUseDeferredValueInitialArg = __EXPERIMENTAL__;
 export const disableClientCache = true;

packages/shared/forks/ReactFeatureFlags.test-renderer.js

@@ -81,7 +81,6 @@ export const enableAsyncActions = true;
 
 export const alwaysThrottleRetries = true;
 
-export const useMicrotasksForSchedulingInFabric = false;
 export const passChildrenWhenCloningPersistedNodes = false;
 export const enableUseDeferredValueInitialArg = __EXPERIMENTAL__;
 export const disableClientCache = true;

packages/shared/forks/ReactFeatureFlags.test-renderer.native.js

@@ -80,7 +80,6 @@ export const enableAsyncActions = true;
 
 export const alwaysThrottleRetries = true;
 
-export const useMicrotasksForSchedulingInFabric = false;
 export const passChildrenWhenCloningPersistedNodes = false;
 export const enableUseDeferredValueInitialArg = __EXPERIMENTAL__;
 export const disableClientCache = true;

packages/shared/forks/ReactFeatureFlags.test-renderer.www.js

@@ -81,7 +81,6 @@ export const enableAsyncActions = true;
 
 export const alwaysThrottleRetries = true;
 
-export const useMicrotasksForSchedulingInFabric = false;
 export const passChildrenWhenCloningPersistedNodes = false;
 export const enableUseDeferredValueInitialArg = true;
 export const disableClientCache = true;

packages/shared/forks/ReactFeatureFlags.www.js

@@ -109,7 +109,6 @@ export const enableFizzExternalRuntime = true;
 
 export const forceConcurrentByDefaultForTesting = false;
 
-export const useMicrotasksForSchedulingInFabric = false;
 export const passChildrenWhenCloningPersistedNodes = false;
 
 export const enableAsyncDebugInfo = false;

scripts/flow/react-native-host-hooks.js

@@ -167,6 +167,8 @@ declare module 'react-native/Libraries/ReactPrivate/ReactNativePrivateInterface'
 declare module 'react-native/Libraries/ReactPrivate/ReactNativePrivateInitializeCore' {
 }
 
+declare const RN$enableMicrotasksInReact: boolean;
+
 // This is needed for a short term solution.
 // See https://github.com/facebook/react/pull/15490 for more info
 declare var nativeFabricUIManager: {

scripts/flow/xplat.js

@@ -18,6 +18,5 @@ declare module 'ReactNativeInternalFeatureFlags' {
   declare export var enableUnifiedSyncLane: boolean;
   declare export var enableUseRefAccessWarning: boolean;
   declare export var passChildrenWhenCloningPersistedNodes: boolean;
-  declare export var useMicrotasksForSchedulingInFabric: boolean;
   declare export var useModernStrictMode: boolean;
 }

scripts/rollup/validate/eslintrc.rn.js

@@ -42,6 +42,8 @@ module.exports = {
     // Fabric. See https://github.com/facebook/react/pull/15490
     // for more information
     nativeFabricUIManager: 'readonly',
+    // RN flag to enable microtasks
+    RN$enableMicrotasksInReact: 'readonly',
     // Trusted Types
     trustedTypes: 'readonly',
     // RN supports this