[firebase_messaging]: iOS plugin missing handling call _firebaseMessagingBackgroundHandler callback after migrating to flutter v3.44+

[ziqq]

Is there an existing issue for this?

• I have searched the existing issues.

Are you aware of the differences between iOS and Android background message handling?

• I understand that iOS and Android background messages behave differently, and I've designed my application with that in mind.

Do you have an active Apple Developer account?

• I have an active Apple Developer account.

Are you using a physical iOS device to test background messages?

• I am using a physical iOS device to test background messages.

Have you enabled "Remote Notifications" & "Background Mode" (Checking options for "Background Processing" & "Remote Notifications") in your app's Xcode project?

Yes

Have you created an APNs key in your Apple Developer account & uploaded this APNs key to your Firebase console?

Yes

Have you disabled method swizzling for Firebase in your app?

Yes

Are you sending messages to your app from the Firebase Admin SDK?

admin
  .messaging()
  .sendToDevice(
    [token],
    {
   "senderId":null,
   "category":null,
   "collapseKey":null,
   "contentAvailable":true,
   "data":{
      "visits":[
         {
            "status":"new",
            "duration":"15:30\u201416:15",
            "serviceName":"Service name"
         },
      ],
      "userID":64881,
      "clickAction":"FLUTTER_NOTIFICATION_CLICK",
      "visitID":2500300,
      "notificationCount":78,
      "type":"visits",
      "sound":"default",
      "url":"/cabinet/visits/2500300"
   },
   "from":null,
   "messageId":1781255183960138,
   "messageType":null,
   "mutableContent":true,
   "notification":{
      "title":"Новая запись",
      "titleLocArgs":[
         
      ],
      "titleLocKey":null,
      "body":"15 июня в 17":"00 Услуга":"SPA":"Массаж",
      "bodyLocArgs":[
         
      ],
      "bodyLocKey":null,
      "android":null,
      "apple":{
         "badge":null,
         "subtitle":null,
         "subtitleLocArgs":[
            
         ],
         "subtitleLocKey":null,
         "imageUrl":"",
         "sound":{
            "critical":false,
            "name":"default",
            "volume":1
         }
      },
      "web":null
   },
   "sentTime":null,
   "threadId":null,
   "ttl":null
}
  )

Have you requested permission from the user to receive notifications?

• I have the relevant permission to receive notifications.

Have you used the 'Console' application on your macOS device to check if the iOS device's system is throttling your background messages?

Yes. But didReceiveRemoteNotification not called.

Additional context and comments

Missing handling call _firebaseMessagingBackgroundHandler callback after migrating to flutter v3.44+.
Before Flutter v3.44+, everything worked with the current payload.

My AppDelegate

import UIKit
import Flutter
import Firebase
import FirebaseMessaging
import UserNotifications

@main
@objc class AppDelegate: FlutterAppDelegate, FlutterImplicitEngineDelegate, MessagingDelegate {
    override func application(_ application: UIApplication,
                              didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        FirebaseApp.configure()

        UNUserNotificationCenter.current().delegate = self

        application.registerForRemoteNotifications()

        UIApplication.shared.setMinimumBackgroundFetchInterval(TimeInterval(60*15))

        return super.application(application, didFinishLaunchingWithOptions: launchOptions)
    }

    func didInitializeImplicitFlutterEngine(_ engineBridge: FlutterImplicitEngineBridge) {
        GeneratedPluginRegistrant.register(with: engineBridge.pluginRegistry)
    }

    override func application(_ application: UIApplication,
                              didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        Messaging.messaging().apnsToken = deviceToken
        super.application(application, didRegisterForRemoteNotificationsWithDeviceToken: deviceToken)
    }

    override func application(
        _ application: UIApplication,
        didReceiveRemoteNotification userInfo: [AnyHashable: Any],
        fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void
    ) {
        print("FCM didReceiveRemoteNotification | state=\(application.applicationState.rawValue) userInfo=\(userInfo)")
        Messaging.messaging().appDidReceiveMessage(userInfo)

        // Handle the notification natively since Flutter's handler doesn't work
        if let type = userInfo["type"] as? String, type == "visits" {
            print("FCM didReceiveRemoteNotification | Received 'visits' notification, processing natively")
            // Process notification here
            // completionHandler(.newData)
            // return
        }

        super.application(
            application,
            didReceiveRemoteNotification: userInfo,
            fetchCompletionHandler: completionHandler
        )
    }

    // If APNs registration fails, display an error message.
    override func application(_ application: UIApplication,
                              didFailToRegisterForRemoteNotificationsWithError error: Error) {
        print("APNs register failed: \(error)")
        super.application(application, didFailToRegisterForRemoteNotificationsWithError: error)
    }

    // Call when a notification is delivered to a foreground app.
    override func userNotificationCenter(
        _ center: UNUserNotificationCenter,
        willPresent notification: UNNotification,
        withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void
    ) {
        let userInfo = notification.request.content.userInfo
        Messaging.messaging().appDidReceiveMessage(userInfo)

        super.userNotificationCenter(center, willPresent: notification) { options in
            if #available(iOS 14.0, *) {
                completionHandler(options.union([.banner, .list, .sound]))
            } else {
                completionHandler(options.union([.alert, .sound]))
            }
        }
    }
}

[SelaseKay]

Hi @ziqq, thanks for the report. Could you provide some additional context? Please include detailed, reproducible steps and clearly describe the expected behavior versus the actual behavior you're observing. Also, share a minimal reproducible example app that I can clone to reproduce the issue on my end.

[ziqq]

Hi @SelaseKay,

It'll be difficult to provide an example since I'm working on a commercial project. In short, the gist is this: before updating Flutter to 3.44+, everything worked as expected, meaning _firebaseMessagingBackgroundHandler worked fine. However, after the upgrade, this handler stopped working, even though the payloads had been configured and working for a long time.

[SelaseKay]

Hi @ziqq, without a minimal example app I can clone, it will be difficult to investigate this further as I'm unable to reproduce this issue with the firebase_messaging example app. You mentioned in your issue description that you have disable swizzling which is a requirement of the plugin to work properly as stated here: https://firebase.google.com/docs/cloud-messaging/flutter/get-started#method-swizzling. Also, what version of firebase_messaging are you experiencing this on?

[ziqq]

@SelaseKay, I'm using latest firebase_messaging version

[SelaseKay]

@ziqq, thanks for the update. As mentioned in my previous comment, we'll need a minimal reproducible example to investigate this further. In the meantime, please try enabling swizzling and let us know whether that resolves the issue.