Automate setting the RCTNewArchEnabled flag

packages/react-native/Libraries/AppDelegate/RCTArchConfiguratorProtocol.h

@@ -15,22 +15,22 @@ NS_ASSUME_NONNULL_BEGIN
 ///
 /// @note: This is required to be rendering on Fabric (i.e. on the New Architecture).
 /// @return: `true` if the Turbo Native Module are enabled. Otherwise, it returns `false`.
-- (BOOL)turboModuleEnabled __attribute__((deprecated("Use newArchEnabled instead")));
+- (BOOL)turboModuleEnabled __attribute__((deprecated("Use RCTIsNewArchEnabled instead")));
 
 /// This method controls whether the App will use the Fabric renderer of the New Architecture or not.
 ///
 /// @return: `true` if the Fabric Renderer is enabled. Otherwise, it returns `false`.
-- (BOOL)fabricEnabled __attribute__((deprecated("Use newArchEnabled instead")));
+- (BOOL)fabricEnabled __attribute__((deprecated("Use RCTIsNewArchEnabled instead")));
 
 /// This method controls whether React Native's new initialization layer is enabled.
 ///
 /// @return: `true` if the new initialization layer is enabled. Otherwise returns `false`.
-- (BOOL)bridgelessEnabled __attribute__((deprecated("Use newArchEnabled instead")));
+- (BOOL)bridgelessEnabled __attribute__((deprecated("Use RCTIsNewArchEnabled instead")));
 
 /// This method controls whether React Native uses new Architecture.
 ///
 /// @return: `true` if the new architecture is enabled. Otherwise returns `false`.
-- (BOOL)newArchEnabled;
+- (BOOL)newArchEnabled __attribute__((deprecated("Use RCTIsNewArchEnabled instead")));
 @end
 
 NS_ASSUME_NONNULL_END

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

@@ -108,11 +108,7 @@ - (void)hostDidStart:(RCTHost *)host
 
 - (BOOL)newArchEnabled
 {
-#if RCT_NEW_ARCH_ENABLED
-  return YES;
-#else
-  return NO;
-#endif
+  return RCTIsNewArchEnabled();
 }
 
 - (BOOL)bridgelessEnabled

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

@@ -55,7 +55,6 @@ - (instancetype)initWithDelegate:(id<RCTReactNativeFactoryDelegate>)delegate rel
     auto newArchEnabled = [self newArchEnabled];
     auto fabricEnabled = [self fabricEnabled];
 
-    RCTSetNewArchEnabled(newArchEnabled);
     [RCTColorSpaceUtils applyDefaultColorSpace:[self defaultColorSpace]];
     RCTEnableTurboModule([self turboModuleEnabled]);
 
@@ -130,12 +129,7 @@ - (BOOL)newArchEnabled
   if ([_delegate respondsToSelector:@selector(newArchEnabled)]) {
     return _delegate.newArchEnabled;
   }
-
-#if RCT_NEW_ARCH_ENABLED
-  return YES;
-#else
-  return NO;
-#endif
+  return RCTIsNewArchEnabled();
 }
 
 - (BOOL)fabricEnabled

packages/react-native/React/Base/RCTUtils.h

@@ -18,7 +18,9 @@ NS_ASSUME_NONNULL_BEGIN
 
 // Whether the New Architecture is enabled or not
 RCT_EXTERN BOOL RCTIsNewArchEnabled(void);
-RCT_EXTERN void RCTSetNewArchEnabled(BOOL enabled);
+RCT_EXTERN void RCTSetNewArchEnabled(BOOL enabled) __attribute__((deprecated(
+    "This function is now no-op. You need to modify the Info.plist adding a RCTNewArchEnabled bool property to control whether the New Arch is enabled or not")));
+;
 
 // JSON serialization/deserialization
 RCT_EXTERN NSString *__nullable RCTJSONStringify(id __nullable jsonObject, NSError **error);

packages/react-native/React/Base/RCTUtils.m

@@ -37,14 +37,18 @@
 static BOOL _newArchEnabled = false;
 BOOL RCTIsNewArchEnabled(void)
 {
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    NSNumber *rctNewArchEnabled = (NSNumber *)[[NSBundle mainBundle] objectForInfoDictionaryKey:@"RCTNewArchEnabled"];
+    _newArchEnabled = rctNewArchEnabled == nil || rctNewArchEnabled.boolValue;
+  });
   return _newArchEnabled;
 }
 void RCTSetNewArchEnabled(BOOL enabled)
 {
-  static dispatch_once_t onceToken;
-  dispatch_once(&onceToken, ^{
-    _newArchEnabled = enabled;
-  });
+  // This function is now deprecated and will be removed in the future.
+  // This function is now no-op. You need to modify the Info.plist adding a `RCTNewArchEnabled` bool property to control
+  // whether the New Arch is enabled or not.
 }
 
 static NSString *__nullable _RCTJSONStringifyNoRetry(id __nullable jsonObject, NSError **error)

packages/react-native/scripts/cocoapods/new_architecture.rb

@@ -9,6 +9,7 @@
 require_relative "./helpers.rb"
 require_relative "./jsengine.rb"
 
+
 class NewArchitectureHelper
     @@NewArchWarningEmitted = false # Used not to spam warnings to the user.
 
@@ -159,4 +160,40 @@ def self.extract_react_native_version(react_native_path, file_manager: File, jso
     def self.new_arch_enabled
         return ENV["RCT_NEW_ARCH_ENABLED"] == '0' ? false : true
     end
+
+    def self.set_RCTNewArchEnabled_in_info_plist(installer, new_arch_enabled)
+        projectPaths = installer.aggregate_targets
+            .map{ |t| t.user_project }
+            .uniq{ |p| p.path }
+            .map{ |p| p.path }
+
+        excluded_info_plist = ["/Pods", "Tests", "metainternal", ".bundle"]
+        projectPaths.each do |projectPath|
+            projectFolderPath = File.dirname(projectPath)
+            infoPlistFiles = `find #{projectFolderPath} -name "Info.plist"`
+            infoPlistFiles = infoPlistFiles.split("\n").map { |f| f.strip }
+
+            infoPlistFiles.each do |infoPlistFile|
+                # If infoPlistFile contains Pods or tests, skip it
+                should_skip = false
+                excluded_info_plist.each do |excluded|
+                    if infoPlistFile.include? excluded
+                        should_skip = true
+                    end
+                end
+                next if should_skip
+
+                # Read the file as a plist
+                info_plist = Xcodeproj::Plist.read_from_path(infoPlistFile)
+                # Check if it contains the RCTNewArchEnabled key
+                if info_plist["RCTNewArchEnabled"] and info_plist["RCTNewArchEnabled"] == new_arch_enabled
+                    next
+                end
+
+                # Add the key and value to the plist
+                info_plist["RCTNewArchEnabled"] = new_arch_enabled ? true : false
+                Xcodeproj::Plist.write_to_path(info_plist, infoPlistFile)
+            end
+        end
+    end
 end

packages/react-native/scripts/react_native_pods.rb

@@ -451,6 +451,7 @@ def react_native_post_install(
 
   NewArchitectureHelper.set_clang_cxx_language_standard_if_needed(installer)
   NewArchitectureHelper.modify_flags_for_new_architecture(installer, NewArchitectureHelper.new_arch_enabled)
+  NewArchitectureHelper.set_RCTNewArchEnabled_in_info_plist(installer, NewArchitectureHelper.new_arch_enabled)
 
   if ENV['USE_HERMES'] == '0' && ENV['USE_THIRD_PARTY_JSC'] != '1'
     print_jsc_removal_message()