Add env var to compile-out legacy arch (#53975)

Summary:
In this change, we are allowing users to install cocoapods with the RCT_REMOVE_LEGACY_ARCH flag enabled to compile out the legacy architecture.

For it to work, we had to adjust some part of the framework that we forgot about when working on the internal side of this feature.

bypass-github-export-checks

## Changelog:
[iOS][Added] - Added way to set the RCT_REMOVE_LEGACY_ARCH flag from Cocoapods to compile ou the legacy arch

Pull Request resolved: #53975

Test Plan:
Tested locally with RNTester and HelloWorld:

```
cd packages/rn-tester
RCT_REMOVE_LEGACY_ARCH=1 bundle exec pod install
open RNTesterPods.xcworkspace
```

Then build and run and verify that the app keeps running.

Same check with Hello World.

Reviewed By: cortinico

Differential Revision: D83471112

Pulled By: cipolleschi

fbshipit-source-id: e5c8fe4eccb3c25510228f20e9e6da3980b0bf0d

Author: cipolleschi

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

@@ -120,6 +120,7 @@ void RCTAppSetupPrepareApp(UIApplication *application, BOOL turboModuleEnabled)
     RCTTurboModuleManager *turboModuleManager,
     const std::shared_ptr<facebook::react::RuntimeScheduler> &runtimeScheduler)
 {
+#ifndef RCT_REMOVE_LEGACY_ARCH
   // Necessary to allow NativeModules to lookup TurboModules
   [bridge setRCTTurboModuleRegistry:turboModuleManager];
 
@@ -146,12 +147,18 @@ void RCTAppSetupPrepareApp(UIApplication *application, BOOL turboModuleEnabled)
   return std::make_unique<facebook::react::HermesExecutorFactory>(
       facebook::react::RCTJSIExecutorRuntimeInstaller(runtimeInstallerLambda));
 #endif
+#else
+  // This method should not be invoked in the New Arch. So when Legacy Arch is removed, we can
+  // safly return a nullptr.
+  return nullptr;
+#endif
 }
 
 std::unique_ptr<facebook::react::JSExecutorFactory> RCTAppSetupJsExecutorFactoryForOldArch(
     RCTBridge *bridge,
     const std::shared_ptr<facebook::react::RuntimeScheduler> &runtimeScheduler)
 {
+#ifndef RCT_REMOVE_LEGACY_ARCH
   auto runtimeInstallerLambda = [bridge, runtimeScheduler](facebook::jsi::Runtime &runtime) {
     if (!bridge) {
       return;
@@ -164,4 +171,9 @@ void RCTAppSetupPrepareApp(UIApplication *application, BOOL turboModuleEnabled)
   return std::make_unique<facebook::react::HermesExecutorFactory>(
       facebook::react::RCTJSIExecutorRuntimeInstaller(runtimeInstallerLambda));
 #endif
+#else
+  // This method should not be invoked in the New Arch. So when Legacy Arch is removed, we can
+  // safly return a nullptr.
+  return nullptr;
+#endif
 }

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

@@ -261,7 +261,12 @@ - (RCTRootViewFactory *)createRCTRootViewFactory
 
   configuration.sourceURLForBridge = ^NSURL *_Nullable(RCTBridge *_Nonnull bridge)
   {
+#ifndef RCT_REMOVE_LEGACY_ARCH
     return [weakSelf.delegate sourceURLForBridge:bridge];
+#else
+    // When the Legacy Arch is removed, the Delegate does not have a sourceURLForBridge method
+    return [weakSelf.delegate bundleURL];
+#endif
   };
 
   if ([self.delegate respondsToSelector:@selector(extraModulesForBridge:)]) {
@@ -275,13 +280,24 @@ - (RCTRootViewFactory *)createRCTRootViewFactory
     configuration.extraLazyModuleClassesForBridge =
         ^NSDictionary<NSString *, Class> *_Nonnull(RCTBridge *_Nonnull bridge)
     {
+#ifndef RCT_REMOVE_LEGACY_ARCH
       return [weakSelf.delegate extraLazyModuleClassesForBridge:bridge];
+#else
+      // When the Legacy Arch is removed, the Delegate does not have a extraLazyModuleClassesForBridge method
+      return @{};
+#endif
     };
   }
 
   if ([self.delegate respondsToSelector:@selector(bridge:didNotFindModule:)]) {
     configuration.bridgeDidNotFindModule = ^BOOL(RCTBridge *_Nonnull bridge, NSString *_Nonnull moduleName) {
+#ifndef RCT_REMOVE_LEGACY_ARCH
       return [weakSelf.delegate bridge:bridge didNotFindModule:moduleName];
+#else
+      // When the Legacy Arch is removed, the Delegate does not have a bridge:didNotFindModule method
+      // We return NO, because if we have invoked this method is unlikely that the module will be actually registered
+      return NO;
+#endif
     };
   }
 
@@ -290,13 +306,30 @@ - (RCTRootViewFactory *)createRCTRootViewFactory
         ^(RCTBridge *_Nonnull bridge,
           RCTSourceLoadProgressBlock _Nonnull onProgress,
           RCTSourceLoadBlock _Nonnull loadCallback) {
+#ifndef RCT_REMOVE_LEGACY_ARCH
           [weakSelf.delegate loadSourceForBridge:bridge onProgress:onProgress onComplete:loadCallback];
+#else
+          // When the Legacy Arch is removed, the Delegate does not have a
+          // loadSourceForBridge:onProgress:onComplete: method
+          // We then call the loadBundleAtURL:onProgress:onComplete: instead
+          [weakSelf.delegate loadBundleAtURL:self.bundleURL onProgress:onProgress onComplete:loadCallback];
+#endif
         };
   }
 
   if ([self.delegate respondsToSelector:@selector(loadSourceForBridge:withBlock:)]) {
     configuration.loadSourceForBridge = ^(RCTBridge *_Nonnull bridge, RCTSourceLoadBlock _Nonnull loadCallback) {
+#ifndef RCT_REMOVE_LEGACY_ARCH
       [weakSelf.delegate loadSourceForBridge:bridge withBlock:loadCallback];
+#else
+      // When the Legacy Arch is removed, the Delegate does not have a
+      // loadSourceForBridge:withBlock: method
+      // We then call the loadBundleAtURL:onProgress:onComplete: instead
+      [weakSelf.delegate loadBundleAtURL:self.bundleURL
+                              onProgress:^(RCTLoadingProgress *progressData) {
+                              }
+                              onComplete:loadCallback];
+#endif
     };
   }
 

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

@@ -521,6 +521,7 @@ def self.remove_flag_for_key(config, flag, key)
 
         if current_setting.include?(flag)
             current_setting.slice! flag
+            current_setting.strip!
         end
 
         config.build_settings[key] = current_setting

packages/react-native/scripts/react_native_pods.rb

@@ -518,6 +518,12 @@ def react_native_post_install(
   ReactNativePodsUtils.set_build_setting(installer, build_setting: "REACT_NATIVE_PATH", value: File.join("${PODS_ROOT}", "..", react_native_path))
   ReactNativePodsUtils.set_build_setting(installer, build_setting: "SWIFT_ACTIVE_COMPILATION_CONDITIONS", value: ['$(inherited)', 'DEBUG'], config_name: "Debug")
 
+  if (ENV['RCT_REMOVE_LEGACY_ARCH'] == '1')
+    ReactNativePodsUtils.add_compiler_flag_to_project(installer, "-DRCT_REMOVE_LEGACY_ARCH=1")
+  else
+    ReactNativePodsUtils.remove_compiler_flag_from_project(installer, "-DRCT_REMOVE_LEGACY_ARCH=1")
+  end
+
   ReactNativePodsUtils.set_ccache_compiler_and_linker_build_settings(installer, react_native_path, ccache_enabled)
   ReactNativePodsUtils.updateOSDeploymentTarget(installer)
   ReactNativePodsUtils.set_dynamic_frameworks_flags(installer)