feat(auth): expose the missing MultiFactor classes through the universal package

packages/firebase_auth/firebase_auth/lib/firebase_auth.dart

@@ -14,8 +14,8 @@ import 'package:flutter/foundation.dart';
 export 'package:firebase_auth_platform_interface/firebase_auth_platform_interface.dart'
     show
         FirebaseAuthException,
-        FirebaseAuthMultiFactorException,
         MultiFactorInfo,
+        MultiFactorSession,
         PhoneMultiFactorInfo,
         IdTokenResult,
         UserMetadata,

packages/firebase_auth/firebase_auth/lib/src/firebase_auth.dart

@@ -492,10 +492,16 @@ class FirebaseAuth extends FirebasePluginPlatform {
   ///  - Thrown if the credential is a [PhoneAuthProvider.credential] and the
   ///    verification ID of the credential is not valid.id.
   Future<UserCredential> signInWithCredential(AuthCredential credential) async {
-    return UserCredential._(
-      this,
-      await _delegate.signInWithCredential(credential),
-    );
+    try {
+      return UserCredential._(
+        this,
+        await _delegate.signInWithCredential(credential),
+      );
+    } on FirebaseAuthMultiFactorExceptionPlatform catch (e) {
+      throw FirebaseAuthMultiFactorException._(this, e);
+    } catch (e) {
+      rethrow;
+    }
   }
 
   /// Tries to sign in a user with a given custom token.
@@ -519,7 +525,14 @@ class FirebaseAuth extends FirebasePluginPlatform {
   /// - **invalid-custom-token**:
   ///  - Thrown if the custom token format is incorrect.
   Future<UserCredential> signInWithCustomToken(String token) async {
-    return UserCredential._(this, await _delegate.signInWithCustomToken(token));
+    try {
+      return UserCredential._(
+          this, await _delegate.signInWithCustomToken(token));
+    } on FirebaseAuthMultiFactorExceptionPlatform catch (e) {
+      throw FirebaseAuthMultiFactorException._(this, e);
+    } catch (e) {
+      rethrow;
+    }
   }
 
   /// Attempts to sign in a user with the given email address and password.
@@ -545,10 +558,16 @@ class FirebaseAuth extends FirebasePluginPlatform {
     required String email,
     required String password,
   }) async {
-    return UserCredential._(
-      this,
-      await _delegate.signInWithEmailAndPassword(email, password),
-    );
+    try {
+      return UserCredential._(
+        this,
+        await _delegate.signInWithEmailAndPassword(email, password),
+      );
+    } on FirebaseAuthMultiFactorExceptionPlatform catch (e) {
+      throw FirebaseAuthMultiFactorException._(this, e);
+    } catch (e) {
+      rethrow;
+    }
   }
 
   /// Signs in using an email address and email sign-in link.
@@ -570,10 +589,16 @@ class FirebaseAuth extends FirebasePluginPlatform {
     required String email,
     required String emailLink,
   }) async {
-    return UserCredential._(
-      this,
-      await _delegate.signInWithEmailLink(email, emailLink),
-    );
+    try {
+      return UserCredential._(
+        this,
+        await _delegate.signInWithEmailLink(email, emailLink),
+      );
+    } on FirebaseAuthMultiFactorExceptionPlatform catch (e) {
+      throw FirebaseAuthMultiFactorException._(this, e);
+    } catch (e) {
+      rethrow;
+    }
   }
 
   /// Signs in with an AuthProvider using native authentication flow.
@@ -584,10 +609,16 @@ class FirebaseAuth extends FirebasePluginPlatform {
   Future<UserCredential> signInWithAuthProvider(
     AuthProvider provider,
   ) async {
-    return UserCredential._(
-      this,
-      await _delegate.signInWithAuthProvider(provider),
-    );
+    try {
+      return UserCredential._(
+        this,
+        await _delegate.signInWithAuthProvider(provider),
+      );
+    } on FirebaseAuthMultiFactorExceptionPlatform catch (e) {
+      throw FirebaseAuthMultiFactorException._(this, e);
+    } catch (e) {
+      rethrow;
+    }
   }
 
   /// Starts a sign-in flow for a phone number.
@@ -624,15 +655,27 @@ class FirebaseAuth extends FirebasePluginPlatform {
   ///
   /// This method is only available on web based platforms.
   Future<UserCredential> signInWithPopup(AuthProvider provider) async {
-    return UserCredential._(this, await _delegate.signInWithPopup(provider));
+    try {
+      return UserCredential._(this, await _delegate.signInWithPopup(provider));
+    } on FirebaseAuthMultiFactorExceptionPlatform catch (e) {
+      throw FirebaseAuthMultiFactorException._(this, e);
+    } catch (e) {
+      rethrow;
+    }
   }
 
   /// Authenticates a Firebase client using a full-page redirect flow.
   ///
   /// To handle the results and errors for this operation, refer to
   /// [getRedirectResult].
   Future<void> signInWithRedirect(AuthProvider provider) {
-    return _delegate.signInWithRedirect(provider);
+    try {
+      return _delegate.signInWithRedirect(provider);
+    } on FirebaseAuthMultiFactorExceptionPlatform catch (e) {
+      throw FirebaseAuthMultiFactorException._(this, e);
+    } catch (e) {
+      rethrow;
+    }
   }
 
   /// Signs out the current user.

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

@@ -17,10 +17,10 @@ class MultiFactor {
   ///
   /// [displayName] can be used to provide a display name for the second factor.
   Future<void> enroll(
-    MultiFactorAssertionPlatform assertion, {
+    MultiFactorAssertion assertion, {
     String? displayName,
   }) async {
-    return _delegate.enroll(assertion, displayName: displayName);
+    return _delegate.enroll(assertion._delegate, displayName: displayName);
   }
 
   /// Unenrolls a second factor from this user.
@@ -45,9 +45,68 @@ class MultiFactor {
 class PhoneMultiFactorGenerator {
   /// Transforms a PhoneAuthCredential into a [MultiFactorAssertion]
   /// which can be used to confirm ownership of a phone second factor.
-  static MultiFactorAssertionPlatform getAssertion(
+  static MultiFactorAssertion getAssertion(
     PhoneAuthCredential credential,
   ) {
-    return PhoneMultiFactorGeneratorPlatform.instance.getAssertion(credential);
+    final assertion =
+        PhoneMultiFactorGeneratorPlatform.instance.getAssertion(credential);
+    return MultiFactorAssertion._(assertion);
   }
 }
+
+/// Represents an assertion that the Firebase Authentication server
+/// can use to authenticate a user as part of a multi-factor flow.
+class MultiFactorAssertion {
+  final MultiFactorAssertionPlatform _delegate;
+
+  MultiFactorAssertion._(this._delegate) {
+    MultiFactorAssertionPlatform.verifyExtends(_delegate);
+  }
+}
+
+/// Utility class that contains methods to resolve second factor
+/// requirements on users that have opted into two-factor authentication.
+class MultiFactorResolver {
+  final FirebaseAuth _auth;
+  final MultiFactorResolverPlatform _delegate;
+
+  MultiFactorResolver._(this._auth, this._delegate) {
+    MultiFactorResolverPlatform.verifyExtends(_delegate);
+  }
+
+  /// List of [MultiFactorInfo] which represents the available
+  /// second factors that can be used to complete the sign-in for the current session.
+  List<MultiFactorInfo> get hints => _delegate.hints;
+
+  /// A MultiFactorSession, an opaque session identifier for the current sign-in flow.
+  MultiFactorSession get session => _delegate.session;
+
+  /// Completes sign in with a second factor using an MultiFactorAssertion which
+  /// confirms that the user has successfully completed the second factor challenge.
+  Future<UserCredential> resolveSignIn(
+    MultiFactorAssertion assertion,
+  ) async {
+    final credential = await _delegate.resolveSignIn(assertion._delegate);
+    return UserCredential._(_auth, credential);
+  }
+}
+
+/// MultiFactor exception related to Firebase Authentication. Check the error code
+/// and message for more details.
+class FirebaseAuthMultiFactorException extends FirebaseAuthException {
+  final FirebaseAuth _auth;
+  final FirebaseAuthMultiFactorExceptionPlatform _delegate;
+
+  FirebaseAuthMultiFactorException._(this._auth, this._delegate)
+      : super(
+          code: _delegate.code,
+          message: _delegate.message,
+          email: _delegate.email,
+          credential: _delegate.credential,
+          phoneNumber: _delegate.phoneNumber,
+          tenantId: _delegate.tenantId,
+        );
+
+  MultiFactorResolver get resolver =>
+      MultiFactorResolver._(_auth, _delegate.resolver);
+}

packages/firebase_auth/firebase_auth_platform_interface/lib/src/firebase_auth_multi_factor_exception.dart

@@ -8,11 +8,11 @@ import 'package:meta/meta.dart';
 
 /// MultiFactor exception related to Firebase Authentication. Check the error code
 /// and message for more details.
-class FirebaseAuthMultiFactorException extends FirebaseAuthException
+class FirebaseAuthMultiFactorExceptionPlatform extends FirebaseAuthException
     implements Exception {
   // ignore: public_member_api_docs
   @protected
-  FirebaseAuthMultiFactorException({
+  FirebaseAuthMultiFactorExceptionPlatform({
     String? message,
     required String code,
     String? email,

packages/firebase_auth/firebase_auth_platform_interface/lib/src/method_channel/utils/exception.dart

@@ -74,7 +74,7 @@ FirebaseException platformExceptionToFirebaseAuthException(
   );
 }
 
-FirebaseAuthMultiFactorException parseMultiFactorError(
+FirebaseAuthMultiFactorExceptionPlatform parseMultiFactorError(
     Map<String, Object?> details) {
   final code = details['code'] as String?;
   final message = details['message'] as String?;
@@ -124,7 +124,7 @@ FirebaseAuthMultiFactorException parseMultiFactorError(
     auth,
   );
 
-  return FirebaseAuthMultiFactorException(
+  return FirebaseAuthMultiFactorExceptionPlatform(
     code: code ?? 'Unknown',
     message: message,
     resolver: multiFactorResolver,

packages/firebase_auth/firebase_auth_platform_interface/lib/src/platform_interface/platform_interface_multi_factor.dart

@@ -56,20 +56,39 @@ class MultiFactorSession {
   final String id;
 }
 
+/// {@template .multiFactorAssertion}
 /// Represents an assertion that the Firebase Authentication server
 /// can use to authenticate a user as part of a multi-factor flow.
-class MultiFactorAssertionPlatform {}
+/// {@endtemplate}
+class MultiFactorAssertionPlatform extends PlatformInterface {
+  /// {@macro .multiFactorAssertion}
+  MultiFactorAssertionPlatform() : super(token: _token);
+
+  static final Object _token = Object();
+
+  /// Ensures that any delegate class has extended a [MultiFactorResolverPlatform].
+  static void verifyExtends(MultiFactorAssertionPlatform instance) {
+    PlatformInterface.verifyToken(instance, _token);
+  }
+}
 
-/// {@macro .platformInterfaceMultiFactorResolverPlatform}
+/// {@template .platformInterfaceMultiFactorResolverPlatform}
 /// Utility class that contains methods to resolve second factor
 /// requirements on users that have opted into two-factor authentication.
 /// {@endtemplate}
-class MultiFactorResolverPlatform {
+class MultiFactorResolverPlatform extends PlatformInterface {
   /// {@macro .platformInterfaceMultiFactorResolverPlatform}
-  const MultiFactorResolverPlatform(
+  MultiFactorResolverPlatform(
     this.hints,
     this.session,
-  );
+  ) : super(token: _token);
+
+  static final Object _token = Object();
+
+  /// Ensures that any delegate class has extended a [MultiFactorResolverPlatform].
+  static void verifyExtends(MultiFactorResolverPlatform instance) {
+    PlatformInterface.verifyToken(instance, _token);
+  }
 
   /// List of [MultiFactorInfo] which represents the available
   /// second factors that can be used to complete the sign-in for the current session.

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

@@ -50,7 +50,7 @@ FirebaseAuthException getFirebaseAuthException(
       firebaseError as auth_interop.MultiFactorError,
     );
 
-    return FirebaseAuthMultiFactorException(
+    return FirebaseAuthMultiFactorExceptionPlatform(
       code: code,
       message: message,
       email: firebaseError.email,