Enable event loop by default when bridgeless is enabled (#43396)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/43396

Changelog: [General][Changed] Enabled new event loop behavior when bridgeless (new architecture) is enabled.

Reviewed By: rshest

Differential Revision: D54682678

fbshipit-source-id: ff8c45bc1caae0e9182aa94d915d7b6f9427caf9

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

@@ -12,6 +12,8 @@
 #import <React/RCTSurfacePresenterBridgeAdapter.h>
 #import <React/RCTUtils.h>
 #import <objc/runtime.h>
+#import <react/featureflags/ReactNativeFeatureFlags.h>
+#import <react/featureflags/ReactNativeFeatureFlagsDefaults.h>
 #import <react/renderer/graphics/ColorComponents.h>
 #import "RCTAppDelegate+Protected.h"
 #import "RCTAppSetupUtils.h"
@@ -38,6 +40,8 @@
 
 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
 {
+  [self _setUpFeatureFlags];
+
   RCTSetNewArchEnabled([self newArchEnabled]);
   [RCTColorSpaceUtils applyDefaultColorSpace:self.defaultColorSpace];
   RCTAppSetupPrepareApp(application, self.turboModuleEnabled);
@@ -259,4 +263,29 @@
   return [[RCTRootViewFactory alloc] initWithConfiguration:configuration andTurboModuleManagerDelegate:self];
 }
 
+#pragma mark - Feature Flags
+
+class RCTAppDelegateBridgelessFeatureFlags : public facebook::react::ReactNativeFeatureFlagsDefaults {
+ public:
+  bool useModernRuntimeScheduler() override
+  {
+    return true;
+  }
+  bool enableMicrotasks() override
+  {
+    return true;
+  }
+  bool batchRenderingUpdatesInEventLoop() override
+  {
+    return true;
+  }
+};
+
+- (void)_setUpFeatureFlags
+{
+  if ([self bridgelessEnabled]) {
+    facebook::react::ReactNativeFeatureFlags::override(std::make_unique<RCTAppDelegateBridgelessFeatureFlags>());
+  }
+}
+
 @end

packages/react-native/Libraries/AppDelegate/React-RCTAppDelegate.podspec

@@ -91,6 +91,7 @@ Pod::Spec.new do |s|
   add_dependency(s, "React-utils")
   add_dependency(s, "React-debug")
   add_dependency(s, "React-rendererdebug")
+  add_dependency(s, "React-featureflags")
 
   if use_hermes
     s.dependency "React-hermes"

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/defaults/DefaultNewArchitectureEntryPoint.kt

@@ -11,6 +11,8 @@ package com.facebook.react.defaults
 
 import com.facebook.react.common.annotations.VisibleForTesting
 import com.facebook.react.config.ReactFeatureFlags
+import com.facebook.react.internal.featureflags.ReactNativeFeatureFlags
+import com.facebook.react.internal.featureflags.ReactNativeFeatureFlagsDefaults
 
 /**
  * A utility class that serves as an entry point for users setup the New Architecture.
@@ -45,6 +47,17 @@ public object DefaultNewArchitectureEntryPoint {
     ReactFeatureFlags.unstable_useTurboModuleInterop = bridgelessEnabled
     ReactFeatureFlags.enableFabricPendingEventQueue = fabricEnabled
 
+    if (bridgelessEnabled) {
+      ReactNativeFeatureFlags.override(
+          object : ReactNativeFeatureFlagsDefaults() {
+            override fun useModernRuntimeScheduler(): Boolean = true
+
+            override fun enableMicrotasks(): Boolean = true
+
+            override fun batchRenderingUpdatesInEventLoop(): Boolean = true
+          })
+    }
+
     privateFabricEnabled = fabricEnabled
     privateTurboModulesEnabled = turboModulesEnabled
     privateConcurrentReactEnabled = fabricEnabled