[RN] Use microtasks when using bridgeless mode in React Native Fabric renderer (OSS version)

Author: rubennorte

.eslintrc.js

@@ -422,6 +422,12 @@ module.exports = {
         nativeFabricUIManager: 'readonly',
       },
     },
+    {
+      files: ['packages/shared/forks/**/*.js'],
+      globals: {
+        RN$Bridgeless: 'readonly',
+      },
+    },
     {
       files: ['packages/react-server-dom-webpack/**/*.js'],
       globals: {

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

@@ -82,7 +82,10 @@ export const enableAsyncActions = false;
 
 export const alwaysThrottleRetries = false;
 
-export const useMicrotasksForSchedulingInFabric = false;
+const isBridgeless: boolean =
+  typeof RN$Bridgeless !== 'undefined' && !!RN$Bridgeless;
+
+export const useMicrotasksForSchedulingInFabric = isBridgeless;
 export const passChildrenWhenCloningPersistedNodes = false;
 export const enableUseDeferredValueInitialArg = __EXPERIMENTAL__;
 export const disableClientCache = true;

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$Bridgeless: boolean;
+
 // This is needed for a short term solution.
 // See https://github.com/facebook/react/pull/15490 for more info
 declare var nativeFabricUIManager: {

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 Bridgeless mode flag
+    RN$Bridgeless: 'readonly',
     // Trusted Types
     trustedTypes: 'readonly',
     // RN supports this