Unify feature flags for event loop (2nd attempt)

Summary:
Changelog: [internal]

This unifies all the feature flags that control the new event loop on RN. Before, we'd have granular flags for different aspects of it. With this diff, we enable the event loop by default with bridgeless, and we introduce a new flag to explicitly disable it in that case if necessary.

When we're ready to clean up this opt-out, we just need to remove the `&& !ReactNativeFeatureFlags::disableEventLoopOnBridgeless()` conditions.

Reviewed By: fkgozali

Differential Revision: D64464902

packages/react-native/Libraries/AppDelegate/RCTAppDelegate.mm

@@ -307,18 +307,6 @@ - (RCTRootViewFactory *)createRCTRootViewFactory
 
 class RCTAppDelegateBridgelessFeatureFlags : public facebook::react::ReactNativeFeatureFlagsDefaults {
  public:
-  bool useModernRuntimeScheduler() override
-  {
-    return true;
-  }
-  bool enableMicrotasks() override
-  {
-    return true;
-  }
-  bool batchRenderingUpdatesInEventLoop() override
-  {
-    return true;
-  }
   bool enableBridgelessArchitecture() override
   {
     return true;

packages/react-native/Libraries/Core/setUpTimers.js

@@ -21,6 +21,25 @@ if (__DEV__) {
   }
 }
 
+const isEventLoopEnabled = (() => {
+  if (NativeReactNativeFeatureFlags == null) {
+    return false;
+  }
+
+  if (NativeReactNativeFeatureFlags.disableEventLoopOnBridgeless == null) {
+    // Flags not unified yet
+    return (
+      ReactNativeFeatureFlags.useModernRuntimeScheduler() &&
+      ReactNativeFeatureFlags.enableMicrotasks()
+    );
+  } else {
+    return (
+      ReactNativeFeatureFlags.enableBridgelessArchitecture() &&
+      !ReactNativeFeatureFlags.disableEventLoopOnBridgeless()
+    );
+  }
+})();
+
 // In bridgeless mode, timers are host functions installed from cpp.
 if (global.RN$Bridgeless !== true) {
   /**
@@ -48,12 +67,7 @@ if (global.RN$Bridgeless !== true) {
   defineLazyTimer('cancelAnimationFrame');
   defineLazyTimer('requestIdleCallback');
   defineLazyTimer('cancelIdleCallback');
-} else if (
-  // TODO remove this condition when bridgeless == modern scheduler everywhere.
-  NativeReactNativeFeatureFlags != null &&
-  // eslint-disable-next-line react-hooks/rules-of-hooks -- false positive due to `use` prefix
-  ReactNativeFeatureFlags.useModernRuntimeScheduler()
-) {
+} else if (isEventLoopEnabled) {
   polyfillGlobal(
     'requestIdleCallback',
     () =>
@@ -72,10 +86,7 @@ if (global.RN$Bridgeless !== true) {
 // We need to check if the native module is available before accessing the
 // feature flag, because otherwise the API would throw an error in the legacy
 // architecture in OSS, where the native module isn't available.
-if (
-  NativeReactNativeFeatureFlags != null &&
-  ReactNativeFeatureFlags.enableMicrotasks()
-) {
+if (isEventLoopEnabled) {
   // This is the flag that tells React to use `queueMicrotask` to batch state
   // updates, instead of using the scheduler to schedule a regular task.
   // We use a global variable because we don't currently have any other

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlags.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<7d0c7d2dac41c4a64c3c8301b3865fdd>>
+ * @generated SignedSource<<9735aa2b6c596980927a6899b528cad7>>
  */
 
 /**
@@ -41,16 +41,16 @@ public object ReactNativeFeatureFlags {
   public fun allowRecursiveCommitsWithSynchronousMountOnAndroid(): Boolean = accessor.allowRecursiveCommitsWithSynchronousMountOnAndroid()
 
   /**
-   * When enabled, the RuntimeScheduler processing the event loop will batch all rendering updates and dispatch them together at the end of each iteration of the loop.
+   * Do not wait for a main-thread dispatch to complete init to start executing work on the JS thread on Android
    */
   @JvmStatic
-  public fun batchRenderingUpdatesInEventLoop(): Boolean = accessor.batchRenderingUpdatesInEventLoop()
+  public fun completeReactInstanceCreationOnBgThreadOnAndroid(): Boolean = accessor.completeReactInstanceCreationOnBgThreadOnAndroid()
 
   /**
-   * Do not wait for a main-thread dispatch to complete init to start executing work on the JS thread on Android
+   * The bridgeless architecture enables the event loop by default. This feature flag allows us to force disabling it in specific instances.
    */
   @JvmStatic
-  public fun completeReactInstanceCreationOnBgThreadOnAndroid(): Boolean = accessor.completeReactInstanceCreationOnBgThreadOnAndroid()
+  public fun disableEventLoopOnBridgeless(): Boolean = accessor.disableEventLoopOnBridgeless()
 
   /**
    * Kill-switch to turn off support for aling-items:baseline on Fabric iOS.
@@ -142,12 +142,6 @@ public object ReactNativeFeatureFlags {
   @JvmStatic
   public fun enableLongTaskAPI(): Boolean = accessor.enableLongTaskAPI()
 
-  /**
-   * Enables the use of microtasks in Hermes (scheduling) and RuntimeScheduler (execution).
-   */
-  @JvmStatic
-  public fun enableMicrotasks(): Boolean = accessor.enableMicrotasks()
-
   /**
    * Moves execution of pre-mount items to outside the choregrapher in the main thread, so we can estimate idle time more precisely (Android only).
    */
@@ -268,12 +262,6 @@ public object ReactNativeFeatureFlags {
   @JvmStatic
   public fun useImmediateExecutorInAndroidBridgeless(): Boolean = accessor.useImmediateExecutorInAndroidBridgeless()
 
-  /**
-   * When enabled, it uses the modern fork of RuntimeScheduler that allows scheduling tasks with priorities from any thread.
-   */
-  @JvmStatic
-  public fun useModernRuntimeScheduler(): Boolean = accessor.useModernRuntimeScheduler()
-
   /**
    * When enabled, the native view configs are used in bridgeless mode.
    */

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsCxxAccessor.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<cdc39ace2bf8ed5626ae6a4d1526fd6c>>
+ * @generated SignedSource<<dcbe660a6bb8b4dbfaf8f349b3350448>>
  */
 
 /**
@@ -22,8 +22,8 @@ package com.facebook.react.internal.featureflags
 public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccessor {
   private var commonTestFlagCache: Boolean? = null
   private var allowRecursiveCommitsWithSynchronousMountOnAndroidCache: Boolean? = null
-  private var batchRenderingUpdatesInEventLoopCache: Boolean? = null
   private var completeReactInstanceCreationOnBgThreadOnAndroidCache: Boolean? = null
+  private var disableEventLoopOnBridgelessCache: Boolean? = null
   private var enableAlignItemsBaselineOnFabricIOSCache: Boolean? = null
   private var enableAndroidLineHeightCenteringCache: Boolean? = null
   private var enableBridgelessArchitectureCache: Boolean? = null
@@ -39,7 +39,6 @@ public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccesso
   private var enableLayoutAnimationsOnAndroidCache: Boolean? = null
   private var enableLayoutAnimationsOnIOSCache: Boolean? = null
   private var enableLongTaskAPICache: Boolean? = null
-  private var enableMicrotasksCache: Boolean? = null
   private var enablePreciseSchedulingForPremountItemsOnAndroidCache: Boolean? = null
   private var enablePropsUpdateReconciliationAndroidCache: Boolean? = null
   private var enableReportEventPaintTimeCache: Boolean? = null
@@ -60,7 +59,6 @@ public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccesso
   private var traceTurboModulePromiseRejectionsOnAndroidCache: Boolean? = null
   private var useFabricInteropCache: Boolean? = null
   private var useImmediateExecutorInAndroidBridgelessCache: Boolean? = null
-  private var useModernRuntimeSchedulerCache: Boolean? = null
   private var useNativeViewConfigsInBridgelessModeCache: Boolean? = null
   private var useOptimisedViewPreallocationOnAndroidCache: Boolean? = null
   private var useOptimizedEventBatchingOnAndroidCache: Boolean? = null
@@ -86,20 +84,20 @@ public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccesso
     return cached
   }
 
-  override fun batchRenderingUpdatesInEventLoop(): Boolean {
-    var cached = batchRenderingUpdatesInEventLoopCache
+  override fun completeReactInstanceCreationOnBgThreadOnAndroid(): Boolean {
+    var cached = completeReactInstanceCreationOnBgThreadOnAndroidCache
     if (cached == null) {
-      cached = ReactNativeFeatureFlagsCxxInterop.batchRenderingUpdatesInEventLoop()
-      batchRenderingUpdatesInEventLoopCache = cached
+      cached = ReactNativeFeatureFlagsCxxInterop.completeReactInstanceCreationOnBgThreadOnAndroid()
+      completeReactInstanceCreationOnBgThreadOnAndroidCache = cached
     }
     return cached
   }
 
-  override fun completeReactInstanceCreationOnBgThreadOnAndroid(): Boolean {
-    var cached = completeReactInstanceCreationOnBgThreadOnAndroidCache
+  override fun disableEventLoopOnBridgeless(): Boolean {
+    var cached = disableEventLoopOnBridgelessCache
     if (cached == null) {
-      cached = ReactNativeFeatureFlagsCxxInterop.completeReactInstanceCreationOnBgThreadOnAndroid()
-      completeReactInstanceCreationOnBgThreadOnAndroidCache = cached
+      cached = ReactNativeFeatureFlagsCxxInterop.disableEventLoopOnBridgeless()
+      disableEventLoopOnBridgelessCache = cached
     }
     return cached
   }
@@ -239,15 +237,6 @@ public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccesso
     return cached
   }
 
-  override fun enableMicrotasks(): Boolean {
-    var cached = enableMicrotasksCache
-    if (cached == null) {
-      cached = ReactNativeFeatureFlagsCxxInterop.enableMicrotasks()
-      enableMicrotasksCache = cached
-    }
-    return cached
-  }
-
   override fun enablePreciseSchedulingForPremountItemsOnAndroid(): Boolean {
     var cached = enablePreciseSchedulingForPremountItemsOnAndroidCache
     if (cached == null) {
@@ -428,15 +417,6 @@ public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccesso
     return cached
   }
 
-  override fun useModernRuntimeScheduler(): Boolean {
-    var cached = useModernRuntimeSchedulerCache
-    if (cached == null) {
-      cached = ReactNativeFeatureFlagsCxxInterop.useModernRuntimeScheduler()
-      useModernRuntimeSchedulerCache = cached
-    }
-    return cached
-  }
-
   override fun useNativeViewConfigsInBridgelessMode(): Boolean {
     var cached = useNativeViewConfigsInBridgelessModeCache
     if (cached == null) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsCxxInterop.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<b3c3d5419ec8999d61c562e6db8d5289>>
+ * @generated SignedSource<<731105cf7807fd9a3c929c92de91be90>>
  */
 
 /**
@@ -32,10 +32,10 @@ public object ReactNativeFeatureFlagsCxxInterop {
 
   @DoNotStrip @JvmStatic public external fun allowRecursiveCommitsWithSynchronousMountOnAndroid(): Boolean
 
-  @DoNotStrip @JvmStatic public external fun batchRenderingUpdatesInEventLoop(): Boolean
-
   @DoNotStrip @JvmStatic public external fun completeReactInstanceCreationOnBgThreadOnAndroid(): Boolean
 
+  @DoNotStrip @JvmStatic public external fun disableEventLoopOnBridgeless(): Boolean
+
   @DoNotStrip @JvmStatic public external fun enableAlignItemsBaselineOnFabricIOS(): Boolean
 
   @DoNotStrip @JvmStatic public external fun enableAndroidLineHeightCentering(): Boolean
@@ -66,8 +66,6 @@ public object ReactNativeFeatureFlagsCxxInterop {
 
   @DoNotStrip @JvmStatic public external fun enableLongTaskAPI(): Boolean
 
-  @DoNotStrip @JvmStatic public external fun enableMicrotasks(): Boolean
-
   @DoNotStrip @JvmStatic public external fun enablePreciseSchedulingForPremountItemsOnAndroid(): Boolean
 
   @DoNotStrip @JvmStatic public external fun enablePropsUpdateReconciliationAndroid(): Boolean
@@ -108,8 +106,6 @@ public object ReactNativeFeatureFlagsCxxInterop {
 
   @DoNotStrip @JvmStatic public external fun useImmediateExecutorInAndroidBridgeless(): Boolean
 
-  @DoNotStrip @JvmStatic public external fun useModernRuntimeScheduler(): Boolean
-
   @DoNotStrip @JvmStatic public external fun useNativeViewConfigsInBridgelessMode(): Boolean
 
   @DoNotStrip @JvmStatic public external fun useOptimisedViewPreallocationOnAndroid(): Boolean

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsDefaults.kt

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<5613f8d9d9403d005becbbd9348882c6>>
+ * @generated SignedSource<<246695bd5949b60404bf5fa9d1c6a9da>>
  */
 
 /**
@@ -27,10 +27,10 @@ public open class ReactNativeFeatureFlagsDefaults : ReactNativeFeatureFlagsProvi
 
   override fun allowRecursiveCommitsWithSynchronousMountOnAndroid(): Boolean = false
 
-  override fun batchRenderingUpdatesInEventLoop(): Boolean = false
-
   override fun completeReactInstanceCreationOnBgThreadOnAndroid(): Boolean = false
 
+  override fun disableEventLoopOnBridgeless(): Boolean = false
+
   override fun enableAlignItemsBaselineOnFabricIOS(): Boolean = true
 
   override fun enableAndroidLineHeightCentering(): Boolean = false
@@ -61,8 +61,6 @@ public open class ReactNativeFeatureFlagsDefaults : ReactNativeFeatureFlagsProvi
 
   override fun enableLongTaskAPI(): Boolean = false
 
-  override fun enableMicrotasks(): Boolean = false
-
   override fun enablePreciseSchedulingForPremountItemsOnAndroid(): Boolean = false
 
   override fun enablePropsUpdateReconciliationAndroid(): Boolean = false
@@ -103,8 +101,6 @@ public open class ReactNativeFeatureFlagsDefaults : ReactNativeFeatureFlagsProvi
 
   override fun useImmediateExecutorInAndroidBridgeless(): Boolean = false
 
-  override fun useModernRuntimeScheduler(): Boolean = false
-
   override fun useNativeViewConfigsInBridgelessMode(): Boolean = false
 
   override fun useOptimisedViewPreallocationOnAndroid(): Boolean = false