[app_check]: iOS build fails with "Cannot find 'RecaptchaProvider' in scope" and "Redundant conformance of 'FlutterError'"

[Camille-D]

Which plugins are affected?

App Check

Which platforms are affected?

iOS, macOS (any platform where the "recaptcha" Apple/Web provider switch case in FirebaseAppCheckPlugin.swift is compiled — this fails at compile time regardless of which provider is actually activated at runtime)

Description

firebase_app_check 0.4.6 and 0.4.7 fail to build on iOS with two Swift compiler errors, unrelated to which App Check provider the app actually activates (we only use AppleDebugProvider, never reCAPTCHA):

1. Cannot find 'RecaptchaProvider' in scope

Introduced in PR #18505 ("rCE provider api update", merged 2026-08-03), FirebaseAppCheckPlugin.swift calls:

delegateProvider = RecaptchaProvider(app: app, siteKey: recaptchaSiteKey)

AppCheckCore (resolved at 11.3.1 in our lockfile) does not expose a class named RecaptchaProvider. The actual class is AppCheckRecaptchaProvider, declared in AppCheckCore/AppCheckRecaptchaProvider/Sources/Public/AppCheckRecaptchaProvider.swift:

public final class AppCheckRecaptchaProvider: NSObject, AppCheckCoreProvider {

Renaming the call site to AppCheckRecaptchaProvider(app: app, siteKey: recaptchaSiteKey) does not fix it either — AppCheckCore is not implicitly imported by FirebaseAppCheckPlugin.swift (only FirebaseAppCheck and FirebaseCore are), so the type isn't in scope at all until import AppCheckCore is added. Even after adding that import, the constructor signature and protocol conformance have changed too: AppCheckRecaptchaProvider conforms to AppCheckCoreProvider, not AppCheckProvider, and its initializer takes resourceName/APIKey parameters, not app/siteKey. So this isn't a simple rename — the "recaptcha" case in configure(app:providerName:debugToken:recaptchaSiteKey:) needs a real rewrite against the current AppCheckRecaptchaProvider API.

2. Redundant conformance of 'FlutterError' to protocol 'Error'

FirebaseAppCheckPlugin.swift declares:

// swift-format-ignore: AvoidRetroactiveConformances
extension FlutterError: @retroactive Error {}

Several other Firebase Flutter plugins already linked into a typical app declare this exact same extension in their own Swift plugin file (confirmed present in cloud_functions, firebase_storage, firebase_remote_config, firebase_analytics — at both their currently-latest versions and several versions back). Any app that also depends on one of those (which is effectively every non-trivial FlutterFire app) gets a "redundant conformance" compile error as soon as firebase_app_check is added, independent of the firebase_core version in use — we reproduced it with firebase_core pinned all the way back to 4.13.0 (the last release before its own Objective-C→Swift rewrite in 4.14.0), so it isn't specific to that rewrite either.

Reproducing the issue

1. Create a fresh Flutter app (or use an existing one) that already depends on at least one other Firebase plugin whose Swift implementation declares extension FlutterError: @retroactive Error {} — e.g. cloud_functions, firebase_storage, firebase_remote_config, or firebase_analytics.
2. Add firebase_app_check: ^0.4.6 (or ^0.4.7).
3. flutter pub get, then cd ios && rm -rf Pods Podfile.lock && pod install (or just flutter run -d <ios-simulator>), targeting iOS.
4. Build fails with both errors above, regardless of whether FirebaseAppCheck.instance.activate(...) is ever called with a debug/device-check/app-attest provider — the file fails to compile, not just to run.

We did not need to actually invoke the "recaptcha" provider at runtime to hit this — Swift has to type-check the whole switch statement in configure(...) regardless of which case executes.

Firebase Core version

4.14.0 (also reproduced with 4.13.0, see above)

Flutter Version

3.44.1 (stable)

Relevant Log Output

Swift Compiler Error (Xcode): Redundant conformance of 'FlutterError' to protocol 'Error'
.../firebase_app_check-0.4.6/ios/firebase_app_check/Sources/firebase_app_check/FirebaseAppCheckPlugin.swift:23:37

Swift Compiler Error (Xcode): Cannot find 'RecaptchaProvider' in scope
.../firebase_app_check-0.4.6/ios/firebase_app_check/Sources/firebase_app_check/FirebaseAppCheckPlugin.swift:381:29

Could not build the application for the simulator.

Flutter dependencies

Expand Flutter dependencies snippet

firebase_app_check 0.4.6
firebase_core 4.14.0
cloud_functions 6.4.0
firebase_storage 13.5.0
firebase_remote_config 6.6.0
firebase_auth 6.6.1

Additional context and comments

This blocks any app using firebase_app_check on iOS alongside cloud_functions/firebase_storage/firebase_remote_config/firebase_analytics, which is likely a very common combination.

Possible fix direction for the "recaptcha" case: update it to construct AppCheckRecaptchaProvider with its current initializer (resourceName/APIKey, conforming to AppCheckCoreProvider rather than AppCheckProvider) and add import AppCheckCore to FirebaseAppCheckPlugin.swift, since it isn't currently re-exported through FirebaseAppCheck. For the duplicate FlutterError conformance, since several sibling plugins already declare it, firebase_app_check likely doesn't need its own copy at all.

[SelaseKay]

Hi @Camille-D, thanks for the report. I'm looking into this.

[SelaseKay]

Hi @Camille-D, thanks again for the detailed report.

The FlutterError redundant conformance is real on 0.4.6 + firebase_core 4.14.0 — we reproduced that exact error. It's already gone in 0.4.7 (#18569). Could you upgrade and confirm?

firebase_app_check: ^0.4.7
firebase_core: ^4.14.0

We couldn't reproduce Cannot find 'RecaptchaProvider' in scope on 0.4.7 (CocoaPods, with and without use_modular_headers!). If you still see it after upgrading, please paste a minimal repro on this thread: a tiny app with only firebase_core + firebase_app_check 0.4.7, your ios/Podfile, Podfile.lock (FirebaseAppCheck / AppCheckCore versions), and the full Xcode log.