RCT_EXTERN_MODULE Swift modules broken in Xcode 10.2

🐛 Bug Report

It appears Obj-C runtime got more strict with Swift ABI stability in Xcode 10.2 and now causes a crash at runtime when trying to load modules that have Swift implementations. This is the crash error:

Swift class extensions and categories on Swift classes are not allowed to have +load methods

To Reproduce

Create a RN NativeModule e.g.

BadgeHandler.m

#import <React/RCTBridgeModule.h>

@interface RCT_EXTERN_MODULE(BadgeHandler, NSObject)
    RCT_EXTERN_METHOD(setBadgeNumber:(int *)badgeNumber)
@end

BadgeHandler.swift

import UIKit

@objc(BadgeHandler)
class BadgeHandler: NSObject, RCTBridgeModule {
    static func moduleName() -> String! {
        return "BadgeHandler";
    }

    static func requiresMainQueueSetup() -> Bool {
        return true
    }
    
    @objc func setBadgeNumber(_ badgeNumber: Int) {
        DispatchQueue.main.async {
            UIApplication.shared.applicationIconBadgeNumber = badgeNumber
        }
    }
}

AppName-Bridging-Header.h

#ifndef AppName_Bridging_Header_h
#define AppName_Bridging_Header_h

#import <React/RCTBridgeModule.h>

#endif /* AppName_Bridging_Header_h */

Expected Behavior

The NativeModule would load fine at runtime like it did in previous versions of Xcode

Code Example

See above ^

Environment

  React Native Environment Info:
    System:
      OS: macOS 10.14.3
      CPU: (12) x64 Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
      Memory: 31.36 MB / 32.00 GB
      Shell: 5.3 - /bin/zsh
    Binaries:
      Node: 11.6.0 - /usr/local/bin/node
      Yarn: 1.13.0 - /usr/local/bin/yarn
      npm: 6.5.0 - /usr/local/bin/npm
      Watchman: 4.9.0 - /usr/local/bin/watchman
    SDKs:
      iOS SDK:
        Platforms: iOS 12.2, macOS 10.14, tvOS 12.2, watchOS 5.2
      Android SDK:
        API Levels: 23, 25, 26, 27, 28
        Build Tools: 27.0.3, 28.0.2, 28.0.3
        System Images: android-28 | Google APIs Intel x86 Atom
    IDEs:
      Xcode: 10.2/10E125 - /usr/bin/xcodebuild
    npmPackages:
      react: 16.8.3 => 16.8.3
      react-native: 0.59.1 => 0.59.1

Other

This seems to point to this macro in RCTBridgeModule.h:

https://github.com/facebook/react-native/blob/d9eae2a8093156c8faae0c5ae14546bbc95e7a3d/React/Base/RCTBridgeModule.h#L71-L74

[zienag]

Hi! I’m not very familiar with react-native, but I found myself here because I’m blocked from upgrading to 10.2 by one of dependency that uses react-native.

I have an idea for a fix though:

#define RCT_EXPORT_MODULE(js_name, objc_name) \
RCT_EXTERN void RCTRegisterModule(Class); \
+ (NSString *)moduleName { return @#js_name; } \
__attribute__((constructor)) \
static void RCT_CONCAT(initialize_, objc_name)() { RCTRegisterModule([objc_name class]); }

The problem with this is that RCT_EXPORT_MODULE macro will require objc_name parameter now. As I understand, this is not very convenient, as it is used in many places by users. So another solution is to introduce another macro:

#define RCT_EXPORT_MODULE_NO_LOAD(js_name, objc_name) \
RCT_EXTERN void RCTRegisterModule(Class); \
+ (NSString *)moduleName { return @#js_name; } \
__attribute__((constructor)) \
static void RCT_CONCAT(initialize_, objc_name)() { RCTRegisterModule([objc_name class]); }

And replace call in RCT_EXTERN_REMAP_MODULE to new macro:

#define RCT_EXTERN_REMAP_MODULE(js_name, objc_name, objc_supername) \
  objc_name : objc_supername \
  @end \
  @interface objc_name (RCTExternModule) <RCTBridgeModule> \
  @end \
  @implementation objc_name (RCTExternModule) \
  RCT_EXPORT_MODULE_NO_LOAD(js_name, objc_name)

I’m ok to make a pr, but it will take some time until I figure out how to setup everything.

[davethomas11]

If you can’t update your react-native version to get this fix when it is merged because you are using the Expo fork of react-native. Then add this code ( based on above PR ) to a header file:

/**
 * Same as RCT_EXPORT_MODULE, but uses __attribute__((constructor)) for module
 * registration. Useful for registering swift classes that forbids use of load
 * Used in RCT_EXTERN_REMAP_MODULE
 */
#define RCT_EXPORT_MODULE_NO_LOAD(js_name, objc_name) \
RCT_EXTERN void RCTRegisterModule(Class); \
+ (NSString *)moduleName { return @#js_name; } \
__attribute__((constructor)) static void \
RCT_CONCAT(initialize_, objc_name)() { RCTRegisterModule([objc_name class]); }

#define RCT_EXTERN_MODULE_2(objc_name, objc_supername) \
RCT_EXTERN_REMAP_MODULE_2(, objc_name, objc_supername)

/**
 * Like RCT_EXTERN_MODULE, but allows setting a custom JavaScript name.
 */
#define RCT_EXTERN_REMAP_MODULE_2(js_name, objc_name, objc_supername) \
objc_name : objc_supername \
@end \
@interface objc_name (RCTExternModule) <RCTBridgeModule> \
@end \
@implementation objc_name (RCTExternModule) \
RCT_EXPORT_MODULE_NO_LOAD(js_name, objc_name)

Then in your module .m objective C file import that header file you just created and use RCT_EXTERN_MODULE_2 instead of RCT_EXTERN_MODULE

Example:

#import "RctExternModule2HeaderFileThatYouCreatedReplaceFilenameHere.h"
#import "React/RCTViewManager.h"

@interface RCT_EXTERN_MODULE_2(SomeModuleNameOfYoursHere, RCTViewManager)
@end