RCTThirdPartyComponentsProvider crashes on multi-target iOS apps (ShareExtension, App Clip) #56469

Summary

When an iOS app has multiple targets (e.g., main app + ShareExtension), RCTThirdPartyComponentsProvider.mm crashes because it uses NSDictionary literal syntax that cannot handle nil values.

Environment

• React Native: 0.81.5
• Expo SDK: 54
• New Architecture: Enabled
• iOS targets: Main app + ShareExtension

Problem

Crash

NSInvalidArgumentException: attempt to insert nil object from objects[14]
+[RCTThirdPartyComponentsProvider thirdPartyFabricComponents]

Root Cause

1. Codegen generates a single RCTThirdPartyComponentsProvider.mm shared between all targets
2. It uses NSDictionary literal syntax:

   thirdPartyComponents = @{
       @"RNGoogleSignInButton": NSClassFromString(@"RNGoogleSignInButtonComponentView"),
       @"RNGoogleMobileAdsBannerView": NSClassFromString(@"RNGoogleMobileAdsBannerView"),
       // ...
   };

3. ShareExtension/App Clip targets don't link all libraries (size constraints, API limitations)
4. NSClassFromString() returns nil for unlinked classes
5. NSDictionary literal crashes on nil values

Why existing fix doesn't help

PR #51838 (backported to 0.79, included in 0.81) allows disabling libraries via react-native.config.js. But this doesn't help when:

• Library is enabled for main app
• Library is not linked to secondary target (ShareExtension)
• Both targets share the same codegen output

Proposed Solution

Generate nil-safe code by default:

static inline void SafeAddComponent(NSMutableDictionary *dict, NSString *name, NSString *className) {
    Class cls = NSClassFromString(className);
    if (cls != nil) {
        dict[name] = cls;
    }
}

// ...
NSMutableDictionary *components = [NSMutableDictionary dictionary];
SafeAddComponent(components, @"RNGoogleSignInButton", @"RNGoogleSignInButtonComponentView");
SafeAddComponent(components, @"RNGoogleMobileAdsBannerView", @"RNGoogleMobileAdsBannerView");
thirdPartyComponents = [components copy];

This is backward compatible and handles all multi-target scenarios.

Alternative Solutions

1. Generate target-specific RCTThirdPartyComponentsProvider files
2. Add a codegen option to enable nil-safe generation

Related Issues

• ShareExtension crashes with RCTThirdPartyComponentsProvider on New Architecture MaxAst/expo-share-extension#117 (expo-share-extension users hitting this)
• Disabling autolinking on iOS selectively in react-native.config.js crashes the app during runtime #51077 (similar issue, different trigger)
• Exclude selectively disabled libraries from codegen generation #51078, fix: exclusion of selectively disabled libraries from codegen generation #51838 (partial fix for disabled libraries)

Workaround

Currently using a post-install script to patch the generated file:
MaxAst/expo-share-extension#117 (comment)