問題

公式ドキュメントに従ってiOSの電話認証を実装したら、以下のエラーが吐き出された。

If app delegate swizzling is disabled, remote notifications received by UIApplicationDelegate need to be forwarded to FIRAuth's canHandleNotification: method

flutter version: 2.10.3

解決策

参考：https://github.com/firebase/flutterfire/issues/1102#issuecomment-581202025

リンク内のコードから若干修正した（元のコードだとライブラリがないと怒られた）

ios/Runner/AppDelegate.swift　を以下の内容で上書きする。リビルドすると解決。

import UIKit
import Flutter
import Firebase
import FirebaseAuth
import UserNotifications

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
        FirebaseApp.configure()
        GeneratedPluginRegistrant.register(with: self)
        return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
    override func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        let firebaseAuth = Auth.auth()
        firebaseAuth.setAPNSToken(deviceToken, type: AuthAPNSTokenType.unknown)

    }
    override func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
        let firebaseAuth = Auth.auth()
        if (firebaseAuth.canHandleNotification(userInfo)){
            print(userInfo)
            return
        }
    }
}