Enable synchronous state update dispatching behind a flag (facebook#4…

…3580)

Summary:
Pull Request resolved: facebook#43580

Changelog: [internal]

This introduces a new feature flag to commit state updates synchronously from the UI thread (generally) instead of dispatching them to the JS thread to be processed there. We can do this now because we introduced a UI consistency mechanism in D55024832 to JS would see a consistent revision during the execution of a specific task.

Reviewed By: sammy-SC

Differential Revision: D55083029

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<<20c445fde7a1c2607b58b7797346431f>>
+ * @generated SignedSource<<e3cfdd93315067ed37e7cf93aa60af74>>
  */
 
 /**
@@ -76,6 +76,12 @@ public object ReactNativeFeatureFlags {
   @JvmStatic
   public fun enableSpannableBuildingUnification(): Boolean = accessor.enableSpannableBuildingUnification()
 
+  /**
+   * Dispatches state updates synchronously in Fabric (e.g.: updates the scroll position in the shadow tree synchronously from the main thread).
+   */
+  @JvmStatic
+  public fun enableSynchronousStateUpdates(): Boolean = accessor.enableSynchronousStateUpdates()
+
   /**
    * Ensures that JavaScript always has a consistent view of the state of the UI (e.g.: commits done in other threads are not immediately propagated to JS during its execution).
    */

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<<6e973dcdcdfae14c77a6130207333551>>
+ * @generated SignedSource<<9184044883f829855c2de9db42566287>>
  */
 
 /**
@@ -28,6 +28,7 @@ public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccesso
   private var enableMicrotasksCache: Boolean? = null
   private var enableMountHooksAndroidCache: Boolean? = null
   private var enableSpannableBuildingUnificationCache: Boolean? = null
+  private var enableSynchronousStateUpdatesCache: Boolean? = null
   private var enableUIConsistencyCache: Boolean? = null
   private var inspectorEnableCxxInspectorPackagerConnectionCache: Boolean? = null
   private var inspectorEnableModernCDPRegistryCache: Boolean? = null
@@ -105,6 +106,15 @@ public class ReactNativeFeatureFlagsCxxAccessor : ReactNativeFeatureFlagsAccesso
     return cached
   }
 
+  override fun enableSynchronousStateUpdates(): Boolean {
+    var cached = enableSynchronousStateUpdatesCache
+    if (cached == null) {
+      cached = ReactNativeFeatureFlagsCxxInterop.enableSynchronousStateUpdates()
+      enableSynchronousStateUpdatesCache = cached
+    }
+    return cached
+  }
+
   override fun enableUIConsistency(): Boolean {
     var cached = enableUIConsistencyCache
     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<<0d34567fc05555ae401e7f5180dc8771>>
+ * @generated SignedSource<<4154c0f81f2e5ad7ff03e252c4aa965c>>
  */
 
 /**
@@ -44,6 +44,8 @@ public object ReactNativeFeatureFlagsCxxInterop {
 
   @DoNotStrip @JvmStatic public external fun enableSpannableBuildingUnification(): Boolean
 
+  @DoNotStrip @JvmStatic public external fun enableSynchronousStateUpdates(): Boolean
+
   @DoNotStrip @JvmStatic public external fun enableUIConsistency(): Boolean
 
   @DoNotStrip @JvmStatic public external fun inspectorEnableCxxInspectorPackagerConnection(): 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<<cfb3e4f5d83a939f4b034bc62762837e>>
+ * @generated SignedSource<<c903b5aa8d70665c1104baa6670f8cb1>>
  */
 
 /**
@@ -39,6 +39,8 @@ public open class ReactNativeFeatureFlagsDefaults : ReactNativeFeatureFlagsProvi
 
   override fun enableSpannableBuildingUnification(): Boolean = false
 
+  override fun enableSynchronousStateUpdates(): Boolean = false
+
   override fun enableUIConsistency(): Boolean = false
 
   override fun inspectorEnableCxxInspectorPackagerConnection(): Boolean = false

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsLocalAccessor.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<<8908de9b9d0186f1916d8b55d5854cb2>>
+ * @generated SignedSource<<c087df804587a9a02a0547684d0e9c92>>
  */
 
 /**
@@ -32,6 +32,7 @@ public class ReactNativeFeatureFlagsLocalAccessor : ReactNativeFeatureFlagsAcces
   private var enableMicrotasksCache: Boolean? = null
   private var enableMountHooksAndroidCache: Boolean? = null
   private var enableSpannableBuildingUnificationCache: Boolean? = null
+  private var enableSynchronousStateUpdatesCache: Boolean? = null
   private var enableUIConsistencyCache: Boolean? = null
   private var inspectorEnableCxxInspectorPackagerConnectionCache: Boolean? = null
   private var inspectorEnableModernCDPRegistryCache: Boolean? = null
@@ -117,6 +118,16 @@ public class ReactNativeFeatureFlagsLocalAccessor : ReactNativeFeatureFlagsAcces
     return cached
   }
 
+  override fun enableSynchronousStateUpdates(): Boolean {
+    var cached = enableSynchronousStateUpdatesCache
+    if (cached == null) {
+      cached = currentProvider.enableSynchronousStateUpdates()
+      accessedFeatureFlags.add("enableSynchronousStateUpdates")
+      enableSynchronousStateUpdatesCache = cached
+    }
+    return cached
+  }
+
   override fun enableUIConsistency(): Boolean {
     var cached = enableUIConsistencyCache
     if (cached == null) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/internal/featureflags/ReactNativeFeatureFlagsProvider.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<<7555a704535615fcea44c1261095419a>>
+ * @generated SignedSource<<c39073091ea96d16a352d00def1b5532>>
  */
 
 /**
@@ -39,6 +39,8 @@ public interface ReactNativeFeatureFlagsProvider {
 
   @DoNotStrip public fun enableSpannableBuildingUnification(): Boolean
 
+  @DoNotStrip public fun enableSynchronousStateUpdates(): Boolean
+
   @DoNotStrip public fun enableUIConsistency(): Boolean
 
   @DoNotStrip public fun inspectorEnableCxxInspectorPackagerConnection(): Boolean

packages/react-native/ReactAndroid/src/main/jni/react/featureflags/JReactNativeFeatureFlagsCxxInterop.cpp

@@ -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<<e6f57d186226377e4558f633433aa1fc>>
+ * @generated SignedSource<<db9ab5f48de2fdbee406ddea10125feb>>
  */
 
 /**
@@ -87,6 +87,12 @@ class ReactNativeFeatureFlagsProviderHolder
     return method(javaProvider_);
   }
 
+  bool enableSynchronousStateUpdates() override {
+    static const auto method =
+        getReactNativeFeatureFlagsProviderJavaClass()->getMethod<jboolean()>("enableSynchronousStateUpdates");
+    return method(javaProvider_);
+  }
+
   bool enableUIConsistency() override {
     static const auto method =
         getReactNativeFeatureFlagsProviderJavaClass()->getMethod<jboolean()>("enableUIConsistency");
@@ -155,6 +161,11 @@ bool JReactNativeFeatureFlagsCxxInterop::enableSpannableBuildingUnification(
   return ReactNativeFeatureFlags::enableSpannableBuildingUnification();
 }
 
+bool JReactNativeFeatureFlagsCxxInterop::enableSynchronousStateUpdates(
+    facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop> /*unused*/) {
+  return ReactNativeFeatureFlags::enableSynchronousStateUpdates();
+}
+
 bool JReactNativeFeatureFlagsCxxInterop::enableUIConsistency(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop> /*unused*/) {
   return ReactNativeFeatureFlags::enableUIConsistency();
@@ -216,6 +227,9 @@ void JReactNativeFeatureFlagsCxxInterop::registerNatives() {
       makeNativeMethod(
         "enableSpannableBuildingUnification",
         JReactNativeFeatureFlagsCxxInterop::enableSpannableBuildingUnification),
+      makeNativeMethod(
+        "enableSynchronousStateUpdates",
+        JReactNativeFeatureFlagsCxxInterop::enableSynchronousStateUpdates),
       makeNativeMethod(
         "enableUIConsistency",
         JReactNativeFeatureFlagsCxxInterop::enableUIConsistency),

packages/react-native/ReactAndroid/src/main/jni/react/featureflags/JReactNativeFeatureFlagsCxxInterop.h

@@ -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<<a90ff7ce4734046fd9aab1c501ca22b4>>
+ * @generated SignedSource<<6b33129341a4b68cdbbdbce9f57e4d63>>
  */
 
 /**
@@ -54,6 +54,9 @@ class JReactNativeFeatureFlagsCxxInterop
   static bool enableSpannableBuildingUnification(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
 
+  static bool enableSynchronousStateUpdates(
+    facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
+
   static bool enableUIConsistency(
     facebook::jni::alias_ref<JReactNativeFeatureFlagsCxxInterop>);
 

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlags.cpp

@@ -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<<a5c58cc8c0294fd073f43fda88b908f8>>
+ * @generated SignedSource<<56f79a4cb62a993f9c3a8ea01eed2ab6>>
  */
 
 /**
@@ -53,6 +53,10 @@ bool ReactNativeFeatureFlags::enableSpannableBuildingUnification() {
   return getAccessor().enableSpannableBuildingUnification();
 }
 
+bool ReactNativeFeatureFlags::enableSynchronousStateUpdates() {
+  return getAccessor().enableSynchronousStateUpdates();
+}
+
 bool ReactNativeFeatureFlags::enableUIConsistency() {
   return getAccessor().enableUIConsistency();
 }

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlags.h

@@ -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<<e94d55bad5f8bf6cf933ddc50e3b4886>>
+ * @generated SignedSource<<bab6aad25607059d465d6c80711a4adf>>
  */
 
 /**
@@ -77,6 +77,11 @@ class ReactNativeFeatureFlags {
    */
   RN_EXPORT static bool enableSpannableBuildingUnification();
 
+  /**
+   * Dispatches state updates synchronously in Fabric (e.g.: updates the scroll position in the shadow tree synchronously from the main thread).
+   */
+  RN_EXPORT static bool enableSynchronousStateUpdates();
+
   /**
    * Ensures that JavaScript always has a consistent view of the state of the UI (e.g.: commits done in other threads are not immediately propagated to JS during its execution).
    */

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlagsAccessor.cpp

@@ -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<<2ff39fd4c8330ddca994fc40cdeaaf4c>>
+ * @generated SignedSource<<5b42b33319369b7936662a2608794ba5>>
  */
 
 /**
@@ -173,6 +173,24 @@ bool ReactNativeFeatureFlagsAccessor::enableSpannableBuildingUnification() {
   return flagValue.value();
 }
 
+bool ReactNativeFeatureFlagsAccessor::enableSynchronousStateUpdates() {
+  auto flagValue = enableSynchronousStateUpdates_.load();
+
+  if (!flagValue.has_value()) {
+    // This block is not exclusive but it is not necessary.
+    // If multiple threads try to initialize the feature flag, we would only
+    // be accessing the provider multiple times but the end state of this
+    // instance and the returned flag value would be the same.
+
+    markFlagAsAccessed(8, "enableSynchronousStateUpdates");
+
+    flagValue = currentProvider_->enableSynchronousStateUpdates();
+    enableSynchronousStateUpdates_ = flagValue;
+  }
+
+  return flagValue.value();
+}
+
 bool ReactNativeFeatureFlagsAccessor::enableUIConsistency() {
   auto flagValue = enableUIConsistency_.load();
 
@@ -182,7 +200,7 @@ bool ReactNativeFeatureFlagsAccessor::enableUIConsistency() {
     // be accessing the provider multiple times but the end state of this
     // instance and the returned flag value would be the same.
 
-    markFlagAsAccessed(8, "enableUIConsistency");
+    markFlagAsAccessed(9, "enableUIConsistency");
 
     flagValue = currentProvider_->enableUIConsistency();
     enableUIConsistency_ = flagValue;
@@ -200,7 +218,7 @@ bool ReactNativeFeatureFlagsAccessor::inspectorEnableCxxInspectorPackagerConnect
     // be accessing the provider multiple times but the end state of this
     // instance and the returned flag value would be the same.
 
-    markFlagAsAccessed(9, "inspectorEnableCxxInspectorPackagerConnection");
+    markFlagAsAccessed(10, "inspectorEnableCxxInspectorPackagerConnection");
 
     flagValue = currentProvider_->inspectorEnableCxxInspectorPackagerConnection();
     inspectorEnableCxxInspectorPackagerConnection_ = flagValue;
@@ -218,7 +236,7 @@ bool ReactNativeFeatureFlagsAccessor::inspectorEnableModernCDPRegistry() {
     // be accessing the provider multiple times but the end state of this
     // instance and the returned flag value would be the same.
 
-    markFlagAsAccessed(10, "inspectorEnableModernCDPRegistry");
+    markFlagAsAccessed(11, "inspectorEnableModernCDPRegistry");
 
     flagValue = currentProvider_->inspectorEnableModernCDPRegistry();
     inspectorEnableModernCDPRegistry_ = flagValue;
@@ -236,7 +254,7 @@ bool ReactNativeFeatureFlagsAccessor::useModernRuntimeScheduler() {
     // be accessing the provider multiple times but the end state of this
     // instance and the returned flag value would be the same.
 
-    markFlagAsAccessed(11, "useModernRuntimeScheduler");
+    markFlagAsAccessed(12, "useModernRuntimeScheduler");
 
     flagValue = currentProvider_->useModernRuntimeScheduler();
     useModernRuntimeScheduler_ = flagValue;

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlagsAccessor.h

@@ -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<<a8e0d8c5bc041f814bffb1701a124646>>
+ * @generated SignedSource<<a508f23dce88a9c186d6bd84e65b3af7>>
  */
 
 /**
@@ -39,6 +39,7 @@ class ReactNativeFeatureFlagsAccessor {
   bool enableMicrotasks();
   bool enableMountHooksAndroid();
   bool enableSpannableBuildingUnification();
+  bool enableSynchronousStateUpdates();
   bool enableUIConsistency();
   bool inspectorEnableCxxInspectorPackagerConnection();
   bool inspectorEnableModernCDPRegistry();
@@ -53,7 +54,7 @@ class ReactNativeFeatureFlagsAccessor {
   std::unique_ptr<ReactNativeFeatureFlagsProvider> currentProvider_;
   bool wasOverridden_;
 
-  std::array<std::atomic<const char*>, 12> accessedFeatureFlags_;
+  std::array<std::atomic<const char*>, 13> accessedFeatureFlags_;
 
   std::atomic<std::optional<bool>> commonTestFlag_;
   std::atomic<std::optional<bool>> batchRenderingUpdatesInEventLoop_;
@@ -63,6 +64,7 @@ class ReactNativeFeatureFlagsAccessor {
   std::atomic<std::optional<bool>> enableMicrotasks_;
   std::atomic<std::optional<bool>> enableMountHooksAndroid_;
   std::atomic<std::optional<bool>> enableSpannableBuildingUnification_;
+  std::atomic<std::optional<bool>> enableSynchronousStateUpdates_;
   std::atomic<std::optional<bool>> enableUIConsistency_;
   std::atomic<std::optional<bool>> inspectorEnableCxxInspectorPackagerConnection_;
   std::atomic<std::optional<bool>> inspectorEnableModernCDPRegistry_;

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlagsDefaults.h

@@ -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<<1450d89abc68821fb348574016874719>>
+ * @generated SignedSource<<9fd009411ce19224a3102d2713b0b042>>
  */
 
 /**
@@ -59,6 +59,10 @@ class ReactNativeFeatureFlagsDefaults : public ReactNativeFeatureFlagsProvider {
     return false;
   }
 
+  bool enableSynchronousStateUpdates() override {
+    return false;
+  }
+
   bool enableUIConsistency() override {
     return false;
   }

packages/react-native/ReactCommon/react/featureflags/ReactNativeFeatureFlagsProvider.h

@@ -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<<d369db4d7cd374081941bff6c6f3e08f>>
+ * @generated SignedSource<<7384eeb8615a45b79cdcceb731d98e9d>>
  */
 
 /**
@@ -33,6 +33,7 @@ class ReactNativeFeatureFlagsProvider {
   virtual bool enableMicrotasks() = 0;
   virtual bool enableMountHooksAndroid() = 0;
   virtual bool enableSpannableBuildingUnification() = 0;
+  virtual bool enableSynchronousStateUpdates() = 0;
   virtual bool enableUIConsistency() = 0;
   virtual bool inspectorEnableCxxInspectorPackagerConnection() = 0;
   virtual bool inspectorEnableModernCDPRegistry() = 0;