From caa8a857a3d2e9e402c93f9e82e12847a74c05f8 Mon Sep 17 00:00:00 2001
From: Riccardo Cipolleschi <cipolleschi@meta.com>
Date: Thu, 20 Mar 2025 10:37:24 -0700
Subject: [PATCH] Add warning when RCT_EXPORT_MODULE is used in New Arch
 (#49897)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/49897

This change introduces the first warning for the New Architecture warning.

When modules are registered through the RCT_EXPORT_MODULE (or its variants) a warning is emitted.

Note: currently it is only emitted on the Xcode console.
I'm looking into ways to emit it also in the RN DevTools console.

## Changelog:
[iOS][Added] - Show warnings in the New Architecture when modules are loaded using RCT_EXPORT_MODULE

Differential Revision: D70789672
---
 packages/react-native/React/Base/RCTBridge.h  |  5 +
 packages/react-native/React/Base/RCTBridge.mm | 94 +++++++++++++++++++
 .../platform/ios/ReactCommon/RCTInstance.mm   | 17 ++++
 3 files changed, 116 insertions(+)

diff --git a/packages/react-native/React/Base/RCTBridge.h b/packages/react-native/React/Base/RCTBridge.h
index 788730bba133..cdfd10f6f6d5 100644
--- a/packages/react-native/React/Base/RCTBridge.h
+++ b/packages/react-native/React/Base/RCTBridge.h
@@ -38,6 +38,11 @@ RCT_EXTERN_C_BEGIN
  */
 NSString *RCTBridgeModuleNameForClass(Class bridgeModuleClass);
 
+/**
+ * This function returns the list of modules that have been registered using the Old Architecture mechanism.
+ */
+NSMutableArray<NSString *> *getModulesLoadedWithOldArch(void);
+
 /**
  * Experimental.
  * Check/set if JSI-bound NativeModule is enabled. By default it's off.
diff --git a/packages/react-native/React/Base/RCTBridge.mm b/packages/react-native/React/Base/RCTBridge.mm
index 32000177fcb5..d163cd49ccbd 100644
--- a/packages/react-native/React/Base/RCTBridge.mm
+++ b/packages/react-native/React/Base/RCTBridge.mm
@@ -42,6 +42,97 @@
   return result;
 }
 
+NSSet<NSString *> *getCoreModuleClasses(void);
+NSSet<NSString *> *getCoreModuleClasses(void)
+{
+  static NSSet<NSString *> *coreModuleClasses = nil;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    coreModuleClasses = [NSSet setWithArray:@[
+      @"RCTViewManager",
+      @"RCTActivityIndicatorViewManager",
+      @"RCTDebuggingOverlayManager",
+      @"RCTModalHostViewManager",
+      @"RCTModalManager",
+      @"RCTRefreshControlManager",
+      @"RCTSafeAreaViewManager",
+      @"RCTScrollContentViewManager",
+      @"RCTScrollViewManager",
+      @"RCTSwitchManager",
+      @"RCTUIManager",
+      @"RCTAccessibilityManager",
+      @"RCTActionSheetManager",
+      @"RCTAlertManager",
+      @"RCTAppearance",
+      @"RCTAppState",
+      @"RCTClipboard",
+      @"RCTDeviceInfo",
+      @"RCTDevLoadingView",
+      @"RCTDevMenu",
+      @"RCTDevSettings",
+      @"RCTDevToolsRuntimeSettingsModule",
+      @"RCTEventDispatcher",
+      @"RCTExceptionsManager",
+      @"RCTI18nManager",
+      @"RCTKeyboardObserver",
+      @"RCTLogBox",
+      @"RCTPerfMonitor",
+      @"RCTPlatform",
+      @"RCTRedBox",
+      @"RCTSourceCode",
+      @"RCTStatusBarManager",
+      @"RCTTiming",
+      @"RCTWebSocketModule",
+      @"RCTNativeAnimatedModule",
+      @"RCTNativeAnimatedTurboModule",
+      @"RCTBlobManager",
+      @"RCTFileReaderModule",
+      @"RCTBundleAssetImageLoader",
+      @"RCTGIFImageDecoder",
+      @"RCTImageEditingManager",
+      @"RCTImageLoader",
+      @"RCTImageStoreManager",
+      @"RCTImageViewManager",
+      @"RCTLocalAssetImageLoader",
+      @"RCTLinkingManager",
+      @"RCTDataRequestHandler",
+      @"RCTFileRequestHandler",
+      @"RCTHTTPRequestHandler",
+      @"RCTNetworking",
+      @"RCTPushNotificationManager",
+      @"RCTSettingsManager",
+      @"RCTBaseTextViewManager",
+      @"RCTBaseTextInputViewManager",
+      @"RCTInputAccessoryViewManager",
+      @"RCTMultilineTextInputViewManager",
+      @"RCTRawTextViewManager",
+      @"RCTSinglelineTextInputViewManager",
+      @"RCTTextViewManager",
+      @"RCTVirtualTextViewManager",
+      @"RCTVibration",
+    ]];
+  });
+
+  return coreModuleClasses;
+}
+
+static NSMutableArray<NSString *> *modulesLoadedWithOldArch;
+void addModuleLoadedWithOldArch(NSString *);
+void addModuleLoadedWithOldArch(NSString *moduleName)
+{
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    modulesLoadedWithOldArch = [NSMutableArray new];
+  });
+
+  [modulesLoadedWithOldArch addObject:moduleName];
+}
+
+NSMutableArray<NSString *> *getModulesLoadedWithOldArch(void)
+{
+  return modulesLoadedWithOldArch;
+}
+
 /**
  * Register the given class as a bridge module. All modules must be registered
  * prior to the first bridge initialization.
@@ -50,6 +141,9 @@
 void RCTRegisterModule(Class);
 void RCTRegisterModule(Class moduleClass)
 {
+  if (RCTIsNewArchEnabled() && ![getCoreModuleClasses() containsObject:[moduleClass description]]) {
+    addModuleLoadedWithOldArch([moduleClass description]);
+  }
   static dispatch_once_t onceToken;
   dispatch_once(&onceToken, ^{
     RCTModuleClasses = [NSMutableArray new];
diff --git a/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTInstance.mm b/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTInstance.mm
index e06167df9640..4778ec2a2689 100644
--- a/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTInstance.mm
+++ b/packages/react-native/ReactCommon/react/runtime/platform/ios/ReactCommon/RCTInstance.mm
@@ -512,9 +512,26 @@ - (void)_loadJSBundle:(NSURL *)sourceURL
         // Set up hot module reloading in Dev only.
         [strongSelf->_performanceLogger markStopForTag:RCTPLScriptDownload];
         [devSettings setupHMRClientWithBundleURL:sourceURL];
+
+        [strongSelf _logOldArchitectureWarnings];
       }];
 }
 
+- (void)_logOldArchitectureWarnings
+{
+  NSMutableArray<NSString *> *modulesInOldArchMode = getModulesLoadedWithOldArch();
+  if (modulesInOldArchMode.count > 0) {
+    NSMutableString *moduleList = [NSMutableString new];
+    for (NSString *moduleName in modulesInOldArchMode) {
+      [moduleList appendFormat:@"- %@\n", moduleName];
+    }
+    RCTLogWarn(
+        @"The following modules have been registered using a RCT_EXPORT_MODULE. That's a Legacy Architecture API. Please migrate to the new approach as described in the https://reactnative.dev/docs/next/turbo-native-modules-introduction#register-the-native-module-in-your-app website or open a PR in the library repository:\n%@",
+        moduleList);
+    [modulesInOldArchMode removeAllObjects];
+  }
+}
+
 - (void)_loadScriptFromSource:(RCTSource *)source
 {
   std::lock_guard<std::mutex> lock(_invalidationMutex);