iOS Turbo Module Backwards Compatibility Build Error

[Zach-Dean-Attractions-io]

Hi,

I am trying to create a Turbo Native Module with backwards compatibility. I am using the create-react-native-library project to scaffold and build my library.

1. Create the library npx create-react-native-library@latest turboModuleWithBackwardsCompat
   • name: turbo-module-with-backwards-compat
   • type: Turbo Module | Kotlin & Objective-C

The library template comes with an example multiply function. I have modified the header files and implementation files as documented

ios/TurboModuleWithBackwardsCompat.h

+ #import <React/RCTBridgeModule.h>
+ #ifdef RCT_NEW_ARCH_ENABLED
#import "generated/RNTurboModuleWithBackwardsCompatSpec/RNTurboModuleWithBackwardsCompatSpec.h"
+ #endif

+ @interface TurboModuleWithBackwardsCompat: NSObject <RCTBridgeModule>
+ @end

+ #ifdef RCT_NEW_ARCH_ENABLED
- @interface TurboModuleWithBackwardsCompat : NSObject <NativeTurboModuleWithBackwardsCompatSpec>
+ @interface TurboModuleWithBackwardsCompat () <NativeTurboModuleWithBackwardsCompatSpec>
@end
+ #endif

ios/TurboModuleWithBackwardsCompat.mm

#import "TurboModuleWithBackwardsCompat.h"

@implementation TurboModuleWithBackwardsCompat
RCT_EXPORT_MODULE()

+ RCT_EXPORT_SYNCHRONOUS_TYPED_METHOD(NSNumber *, multiply:(double)a b:(double)b) {
- - (NSNumber *)multiply:(double)a b:(double)b {
    NSNumber *result = @(a * b);

    return result;
}

+ #ifdef RCT_NEW_ARCH_ENABLED
- (std::shared_ptr<facebook::react::TurboModule>)getTurboModule:
    (const facebook::react::ObjCTurboModule::InitParams &)params
{
    return std::make_shared<facebook::react::NativeTurboModuleWithBackwardsCompatSpecJSI>(params);
}
+ #endif

@end

The podfile is as follows TurboModuleWithBackwardsCompat.podspec.

require "json"

package = JSON.parse(File.read(File.join(__dir__, "package.json")))

Pod::Spec.new do |s|
  s.name         = "TurboModuleWithBackwardsCompat"
  s.version      = package["version"]
  s.summary      = package["description"]
  s.homepage     = package["homepage"]
  s.license      = package["license"]
  s.authors      = package["author"]

  s.platforms    = { :ios => min_ios_version_supported }
  s.source       = { :git => "https://attractions.io.git", :tag => "#{s.version}" }

  s.source_files = "ios/**/*.{h,m,mm,cpp}"
  s.private_header_files = "ios/generated/**/*.h"

  # Use install_modules_dependencies helper to install the dependencies if React Native version >=0.71.0.
  # See https://github.com/facebook/react-native/blob/febf6b7f33fdb4904669f99d795eba4c0f95d7bf/scripts/cocoapods/new_architecture.rb#L79.
  if respond_to?(:install_modules_dependencies, true)
    install_modules_dependencies(s)
  else
    s.dependency "React-Core"
  end

end

The differences I notice against the documentation are:

• s.source_files includes cpp files here and the documentation doesn't. I think this is fine.
• s.source_files includes swift in the documentation and not here. I think this is fine.
• The inclusion of s.private_header_files = "ios/generated/**/*.h", which comes from Library with swift files causes build to fail because of generated umbrella header file including codegen headers callstack/react-native-builder-bob#690

I've then published this library to NPM.

Then I've created a React Native app running version 0.75.0 of React Native so that the legacy architecture should be enabled by default.

1. npx @react-native-community/cli@latest init myAppV75 --version 0.75.0
2. Within the myAppV75 directory, ran: cd ios && bundle install && bundle exec pod install
3. Simplified the App.tsx file to

import React from 'react';
import { SafeAreaView, Text } from 'react-native';

function App(): React.JSX.Element {

  return (
    <SafeAreaView>
      <Text>Hello World!</Text>
    </SafeAreaView>
  );
}

export default App;

4. Ran the app using npx react-native run-ios

The app runs successfully. I've then installed my turbo native module package from NPM.

1. npm install turbo-module-with-backwards-compat
2. Within the myAppV75 directory, ran: cd ios && bundle exec pod install
3. Ran the app using npx react-native run-ios

The app now fails to build. If I open the project in Xcode then I see the error:

myAppV75/node_modules/turbo-module-with-backwards-compat/ios/generated/RNTurboModuleWithBackwardsCompatSpec/RNTurboModuleWithBackwardsCompatSpec.h:45:18 No type named 'EventEmitterCallback' in namespace 'facebook::react'

However, this is coming from a file within the codegen generated code, which the conditional compilation blocks in the header and implementation files should avoid.

To get around this issue I have modified the podspec file to exclude the generated files.

- s.private_header_files = "ios/generated/**/*.h"
+ if ENV['RCT_NEW_ARCH_ENABLED'] == '1' then
+    s.private_header_files = "ios/generated/**/*.h"
+  else
+    s.exclude_files = "ios/generated/**/*"
+  end

I've published these changes to the library as a new version and created a new example app: npx @react-native-community/cli@latest init myAppV75Second --version 0.75.0. I've installed the pods built the app successfully and used the multiply function in the App.tsx file.

Is it correct to need to exclude the generated files like this if the consuming app is running the legacy architecture or am I doing something wrong?

[Zach-Dean-Attractions-io]

I found a thread here: #8 (comment) which recommended changing #ifdef to #if but I still get the same issue.