SwiftUI Firebase Push Notifications appear inside the app

Question

I just set up push notifications on my SwiftUI app and I noticed that when a notification comes it appears even when the user is inside the app! (when the app's state is active)

here is my setup:

class AppDelegate: NSObject, UIApplicationDelegate {
    func application(_ application: UIApplication,
                     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
        FirebaseApp.configure()
        UNUserNotificationCenter.current().delegate = self
        
        UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound]) { (granted, error) in
        }
        
        application.registerForRemoteNotifications()
        Messaging.messaging().delegate = self
        
        return true
    }
}

extension AppDelegate: UNUserNotificationCenterDelegate {
    func userNotificationCenter(
        _ center: UNUserNotificationCenter,
        willPresent notification: UNNotification,
        withCompletionHandler completionHandler:
        @escaping (UNNotificationPresentationOptions) -> Void
    ) {
        completionHandler([[.banner, .sound, .badge]])
    }
    
    func userNotificationCenter(
        _ center: UNUserNotificationCenter,
        didReceive response: UNNotificationResponse,
        withCompletionHandler completionHandler: @escaping () -> Void
    ) {
        completionHandler()
    }
    
    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        Auth.auth().setAPNSToken(deviceToken, type: .unknown)
        Messaging.messaging().apnsToken = deviceToken
    }
    
    func application(_ application: UIApplication, didReceiveRemoteNotification notification: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
        Messaging.messaging().appDidReceiveMessage(notification)
        
        if (Auth.auth().canHandleNotification(notification)) {
            completionHandler(.noData)
            return
        }
    }
}

extension AppDelegate: MessagingDelegate {
    func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String?) {
        let tokenDict = ["token": fcmToken ?? ""]
        
        NotificationCenter.default.post(
            name: Notification.Name("FCMToken"),
            object: nil,
            userInfo: tokenDict)
    }
}

@main
struct popsterApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
    
    var body: some Scene {
        WindowGroup {
            ...
        }
    }
}

I don't know if it's important but I have swizzling enabled! Any idea why this is happening?

Answer 1

Apparently, this block of code was responsible for making push notifications appear when the app is in the foreground:

func userNotificationCenter(
        _ center: UNUserNotificationCenter,
        willPresent notification: UNNotification,
        withCompletionHandler completionHandler:
        @escaping (UNNotificationPresentationOptions) -> Void
    ) {
        completionHandler([[.banner, .sound, .badge]])
    }