fix(auth, web): convert NativeError to FirebaseAuthError (#11258)

* demonstrate that we cannot capture FirebaseError

* update example for testing

* fix(auth, web): get `FirebaseAuthError` from `NativeError` instance

* fix(auth, web): pass correct properties to FirebaseAuthException

* chore: remove print()

* Discard changes to packages/firebase_auth/firebase_auth/example/lib/main.dart

* chore: format

* chore: rm annotation

* chore: make dynamic type Object

* chore: make AuthErrorCustomData class

* chore: use AuthErrorCustomData class, update AuthError condition logic

* fix: use firebase Error code

* fix: use AuthError for interop

* format

* chore: update code comment

* fix: use window_interop.dart file to check Error constructor

packages/firebase_auth/firebase_auth_web/lib/src/interop/auth_interop.dart

@@ -246,7 +246,7 @@ external MultiFactorUserJsImpl multiFactor(
 @JS()
 external MultiFactorResolverJsImpl getMultiFactorResolver(
   AuthJsImpl auth,
-  MultiFactorError error,
+  AuthError error,
 );
 
 @JS('Auth')
@@ -536,11 +536,14 @@ class UserProfile {
   external factory UserProfile({String? displayName, String? photoURL});
 }
 
+@JS()
+@staticInterop
+abstract class AuthError {}
+
 /// An authentication error.
 ///
 /// See: <https://firebase.google.com/docs/reference/js/firebase.auth.Error>.
-@JS('Error')
-abstract class AuthError {
+extension AuthErrorExtension on AuthError {
   external String get code;
   external set code(String s);
   external String get message;
@@ -553,6 +556,18 @@ abstract class AuthError {
   external set tenantId(String s);
   external String get phoneNumber;
   external set phoneNumber(String s);
+  external Object get customData;
+}
+
+@JS()
+@staticInterop
+class AuthErrorCustomData {}
+
+extension AuthErrorCustomDataExtension on AuthErrorCustomData {
+  external String get appName;
+  external String? get email;
+  external String? get phoneNumber;
+  external String? get tenantId;
 }
 
 @JS()
@@ -707,13 +722,6 @@ class MultiFactorAssertionJsImpl {
   external String get factorId;
 }
 
-/// https://firebase.google.com/docs/reference/js/auth.multifactorerror
-@JS('Error')
-@anonymous
-class MultiFactorError extends AuthError {
-  external dynamic get customData;
-}
-
 /// https://firebase.google.com/docs/reference/js/auth.multifactorresolver
 @JS()
 @anonymous

packages/firebase_auth/firebase_auth_web/lib/src/interop/multi_factor.dart

@@ -19,7 +19,7 @@ MultiFactorUser multiFactor(auth.User user) {
 
 /// Given an AppJSImp, return the Auth instance.
 MultiFactorResolver getMultiFactorResolver(
-    auth.Auth auth, auth_interop.MultiFactorError error) {
+    auth.Auth auth, auth.AuthError error) {
   return MultiFactorResolver.fromJsObject(
       auth_interop.getMultiFactorResolver(auth.jsObject, error));
 }

packages/firebase_auth/firebase_auth_web/lib/src/interop/window_interop.dart

@@ -0,0 +1,11 @@
+// Copyright 2023 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+@JS()
+library window_interop;
+
+import 'package:js/js.dart';
+
+@JS('Error')
+external Object get errorConstructor;

packages/firebase_auth/firebase_auth_web/lib/src/utils/web_utils.dart

@@ -4,6 +4,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:io';
+import 'package:js/js_util.dart';
 
 import 'package:firebase_auth_platform_interface/firebase_auth_platform_interface.dart';
 import 'package:firebase_auth_web/firebase_auth_web.dart';
@@ -13,6 +14,33 @@ import 'package:firebase_core_web/firebase_core_web_interop.dart'
 
 import '../interop/auth.dart' as auth_interop;
 import '../interop/multi_factor.dart' as multi_factor_interop;
+import '../interop/window_interop.dart' as window_interop;
+
+/// Workaround test to check whether `e` is practically a FirebaseError.
+///
+/// Ideally we'd check whether `e instanceof FirebaseError` however
+/// there are two definitions of `FirebaseError` in deployed apps, one from
+/// `firebase-auth.js` (which is usually minified) and one from
+/// `firebase-app.js`.
+///
+/// Because they are not the same, the instanceof check fails. Instead, we test
+/// that it is a window.Error (since that's the base class of FirebaseError) and
+/// we check that it defines "customData" property which is on the AuthError but not the FirebaseError it extends
+bool _isFirebaseAuthError(Object e) =>
+    instanceof(e, window_interop.errorConstructor) &&
+    hasProperty(e, 'customData');
+
+bool _hasFirebaseAuthErrorCodeAndMessage(Object e) {
+  if (_isFirebaseAuthError(e)) {
+    String? code = getProperty(e, 'code');
+    String? message = getProperty(e, 'message');
+    if (code == null || !code.startsWith('auth/')) return false;
+    if (message == null || !message.contains('Firebase')) return false;
+    return true;
+  } else {
+    return false;
+  }
+}
 
 /// Given a web error, an [Exception] is returned.
 ///
@@ -22,20 +50,23 @@ FirebaseAuthException getFirebaseAuthException(
   Object exception, [
   auth_interop.Auth? auth,
 ]) {
-  if (exception is! core_interop.FirebaseError) {
+  if (!_hasFirebaseAuthErrorCodeAndMessage(exception)) {
     return FirebaseAuthException(
       code: 'unknown',
       message: 'An unknown error occurred: $exception',
     );
   }
 
   auth_interop.AuthError firebaseError = exception as auth_interop.AuthError;
-
   String code = firebaseError.code.replaceFirst('auth/', '');
   String message = firebaseError.message
       .replaceFirst(' (${firebaseError.code}).', '')
       .replaceFirst('Firebase: ', '');
 
+  // "customData" - see Firebase AuthError docs: https://firebase.google.com/docs/reference/js/auth.autherror
+  final customData =
+      getProperty(exception, 'customData') as auth_interop.AuthErrorCustomData;
+
   if (code == 'multi-factor-auth-required') {
     final _auth = auth;
     if (_auth == null) {
@@ -47,15 +78,15 @@ FirebaseAuthException getFirebaseAuthException(
     }
     final resolverWeb = multi_factor_interop.getMultiFactorResolver(
       _auth,
-      firebaseError as auth_interop.MultiFactorError,
+      exception,
     );
 
     return FirebaseAuthMultiFactorExceptionPlatform(
       code: code,
       message: message,
-      email: firebaseError.email,
-      phoneNumber: firebaseError.phoneNumber,
-      tenantId: firebaseError.tenantId,
+      email: customData.email,
+      phoneNumber: customData.phoneNumber,
+      tenantId: customData.tenantId,
       resolver: MultiFactorResolverWeb(
         resolverWeb.hints.map((e) {
           if (e is multi_factor_interop.PhoneMultiFactorInfo) {
@@ -88,9 +119,9 @@ FirebaseAuthException getFirebaseAuthException(
   return FirebaseAuthException(
     code: code,
     message: message,
-    email: firebaseError.email,
-    phoneNumber: firebaseError.phoneNumber,
-    tenantId: firebaseError.tenantId,
+    email: customData.email,
+    phoneNumber: customData.phoneNumber,
+    tenantId: customData.tenantId,
   );
 }