[firebase_auth]: iOS build fails with 'Undefined symbol: _OBJC_CLASS_' when using firebase_auth 6.1.3

[mandogtent]

Title: iOS build fails with "Undefined symbol: OBJC_CLASS$_FLTFirebaseAuthPlugin" when using firebase_auth 6.1.3

Repository: FirebaseExtended/flutterfire (firebase_auth package)

Summary

Building iOS with firebase_auth 6.1.3 causes a Release link failure: the app fails to link because the Objective-C class FLTFirebaseAuthPlugin is undefined. Pinning firebase_auth to 6.1.2 resolves the issue and a Release build succeeds.

Reproduction steps

1. Set firebase_auth: ^6.1.3 in pubspec.yaml (or upgrade to 6.1.3).
2. flutter clean
3. flutter pub get
4. cd ios && pod install --repo-update
5. xcodebuild -workspace Runner.xcworkspace -scheme Runner -configuration Release -destination 'generic/platform=iOS' clean build CODE_SIGNING_ALLOWED=NO CODE_SIGNING_IDENTITY="" CODE_SIGNING_REQUIRED=NO

Observed

Linker fails with:

Undefined symbols for architecture arm64:
"OBJC_CLASS$_FLTFirebaseAuthPlugin", referenced from:
in GeneratedPluginRegistrant.o
_OBJC$CATEGORY_FLTFirebaseAuthPlugin$_ASPresentation in firebase_auth6
ld: symbol(s) not found for architecture arm64

Diagnosis / Evidence

• The built firebase_auth.framework binary contains Pigeon- and API-related symbols but the Objective-C class symbol for FLTFirebaseAuthPlugin is not exported.
  • Example inspection:
    • strings on firebase_auth.framework shows occurrences of FLTFirebaseAuthPlugin and source file paths, but nm -gU on the same binary does not show _OBJC_CLASS_$_FLTFirebaseAuthPlugin.
• In the 6.1.3 package, + (void)registerWithRegistrar: appears to be present in the macOS implementation but not in the compiled iOS sources that end up in the framework (the iOS source contains only an ASPresentation category stub in the failing version).
• Temporary workaround confirmed: pinning firebase_auth to 6.1.2 then running pod install and a Release xcodebuild yields BUILD SUCCEEDED.

Files/paths referenced

• ios/Runner/GeneratedPluginRegistrant.m references FLTFirebaseAuthPlugin:
  • [FLTFirebaseAuthPlugin registerWithRegistrar:...]
• Plugin source locations (in my environment):
  • .pub-cache/hosted/pub.dev/firebase_auth-6.1.3/ios/firebase_auth/Sources/firebase_auth/FLTFirebaseAuthPlugin.m (contains ASPresentation category only)
  • .pub-cache/hosted/pub.dev/firebase_auth-6.1.3/macos/firebase_auth/Sources/firebase_auth/FLTFirebaseAuthPlugin.m (contains +registerWithRegistrar: implementation)
• Derived products inspected:
  • ~/Library/Developer/Xcode/DerivedData/.../Build/Products/Release-iphoneos/firebase_auth/firebase_auth.framework
  • xcodebuild log: see local xcodebuild.log captured during reproduction

Suggested fixes

• Ensure + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar is implemented and compiled into the iOS target of firebase_auth 6.1.3 (or publish a patch release that restores the iOS registration symbol).
• Optionally add a unit or CI check that builds an iOS Release to detect regressions where the plugin registration symbol is missing.

Temporary workaround

Pin firebase_auth to 6.1.2 in pubspec.yaml and run flutter pub get, then cd ios && pod install --repo-update. This resolves the linker failure.

Additional notes

• CocoaPods in my build emitted a note about base configuration but this did not cause the linker failure; the missing symbol is the root cause.

Logs & artifacts

• I can provide the full xcodebuild.log, nm and strings outputs on request or attach them to the issue.

--
I can open this issue on GitHub if you want — I used this repro locally and pinned the plugin to 6.1.2 as a temporary fix (commit: chore(iOS): pin firebase_auth to 6.1.2 to avoid iOS linker regression).

[mandogtent]

I reproduced the failure locally and uploaded logs for easier inspection:

• xcodebuild log: https://gist.github.com/mandogtent/b186f0ea7fab62fa6a06dadd6b138832
• nm output (firebase_auth framework): https://gist.github.com/mandogtent/1403bf6a03d53603d6e789cda8cf1465
• strings output (firebase_auth framework): https://gist.github.com/mandogtent/914b6a9d4a38b20e56df6de996d6e617

Summary: The Firebase auth framework binary lacks the Objective-C class symbol _OBJC_CLASS_$_FLTFirebaseAuthPlugin while GeneratedPluginRegistrant expects it. Pinning to firebase_auth: 6.1.2 is a temporary workaround that makes Release builds succeed locally. Happy to provide additional artifacts or test a patch release if helpful.

[mandogtent]

I attempted to subscribe programmatically but the GitHub API returned 404 (likely a permission/scope limitation on my token). I'll monitor this issue manually and post updates and patches here as I make progress. Would you like me to attempt a PR now with a local fix (for example, add a small iOS registration shim or a CI test), or wait for maintainers to request a patch?

[mandogtent]

Opened a PR with a minimal iOS shim that prevents the FLTFirebaseAuthPlugin symbol from being stripped: #17935. I verified locally by building iOS Release and confirming is present in the resulting (see nm output). Please let me know if you'd prefer a different approach (CI check or packaging fix) and I can update the PR.

[SelaseKay]

Hi @mandogtent, I'm unable to reproduce this issue on my end. Could you provide a sample reproducible example in the form of a repo I can clone to investigate further?