let NSE-fetch and MainApp run mutually exclusive

DcCore/DcCore/Extensions/UserDefaults+Extensions.swift

@@ -3,7 +3,26 @@ public extension UserDefaults {
     static var hasExtensionAttemptedToSend = "hasExtensionAttemptedToSend"
     static var hasSavedKeyToKeychain = "hasSavedKeyToKeychain"
     static var upgradedKeychainEntry = "upgradedKeychainEntry_"
+    static var mainAppRunningKey = "mainAppRunning"
+    static var nseFetchingKey = "nseFetching"
+
     static var shared: UserDefaults? {
         return UserDefaults(suiteName: "group.chat.delta.ios")
     }
+
+    static var mainAppRunning: Bool {
+        return shared?.bool(forKey: mainAppRunningKey) ?? false
+    }
+
+    static func setMainAppRunning(_ value: Bool = true) {
+        shared?.setValue(value, forKey: mainAppRunningKey)
+    }
+
+    static var nseFetching: Bool {
+        return shared?.bool(forKey: nseFetchingKey) ?? false
+    }
+
+    static func setNseFetching(_ value: Bool = true) {
+        shared?.setValue(value, forKey: nseFetchingKey)
+    }
 }

DcNotificationService/NotificationService.swift

@@ -7,15 +7,24 @@ class NotificationService: UNNotificationServiceExtension {
     override func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {
         guard let bestAttemptContent = (request.content.mutableCopy() as? UNMutableNotificationContent) else { return }
 
+        if UserDefaults.mainAppRunning {
+            contentHandler(silenceNotification(bestAttemptContent))
+            return
+        }
+        UserDefaults.setNseFetching()
+
         // as we're mixing in notifications from accounts without PUSH and we cannot add multiple notifications,
         // it is best to move everything to the same thread - and set just no threadIdentifier
 
         dcAccounts.openDatabase(writeable: false)
         let eventEmitter = dcAccounts.getEventEmitter()
+
         if !dcAccounts.backgroundFetch(timeout: 25) {
+            UserDefaults.setNseFetching(false)
             contentHandler(bestAttemptContent)
             return
         }
+        UserDefaults.setNseFetching(false)
 
         var messageCount = 0
         var uniqueChats: [String: String] = [:]
@@ -70,6 +79,7 @@ class NotificationService: UNNotificationServiceExtension {
 
         // For Delta Chat, it is just fine to do nothing - assume eg. bad network or mail servers not reachable,
         // then a "You have new messages" is the best that can be done.
+        UserDefaults.setNseFetching(false)
     }
 
     private func silenceNotification(_ bestAttemptContent: UNMutableNotificationContent) -> UNMutableNotificationContent {

deltachat-ios/AppDelegate.swift

@@ -55,6 +55,17 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
 
         logger.info("➡️ didFinishLaunchingWithOptions")
 
+        // The NSE ("Notification Service Extension") must not run at the same time as the app.
+        // The other way round, the NSW is not started with the app running.
+        UserDefaults.setMainAppRunning()
+        var pollSeconds = 0
+        while UserDefaults.nseFetching && pollSeconds < 30 {
+            logger.info("➡️ wait for NSE to terminate")
+            usleep(1_000_000)
+            pollSeconds += 1
+        }
+        UserDefaults.setNseFetching(false) // NSE terminated unexpectedly, do not always wait 30 seconds
+
         let webPCoder = SDImageWebPCoder.shared
         SDImageCodersManager.shared.addCoder(webPCoder)
         let svgCoder = SDImageSVGKCoder.shared
@@ -231,6 +242,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
     func applicationWillEnterForeground(_: UIApplication) {
         logger.info("➡️ applicationWillEnterForeground")
         applicationInForeground = true
+        UserDefaults.setMainAppRunning()
         dcAccounts.startIo()
 
         DispatchQueue.global().async { [weak self] in
@@ -271,6 +283,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
     // applicationDidBecomeActive() is called on initial app start _and_ after applicationWillEnterForeground()
     func applicationDidBecomeActive(_: UIApplication) {
         logger.info("➡️ applicationDidBecomeActive")
+        UserDefaults.setMainAppRunning()
         applicationInForeground = true
     }
 
@@ -286,6 +299,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
 
     func applicationWillTerminate(_: UIApplication) {
         logger.info("⬅️ applicationWillTerminate")
+        UserDefaults.setMainAppRunning(false)
         uninstallEventHandler()
         dcAccounts.closeDatabase()
         if let reachability = reachability {
@@ -326,6 +340,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
             } else if app.backgroundTimeRemaining < 10 {
                 logger.info("⬅️ few background time, \(app.backgroundTimeRemaining), stopping")
                 self.dcAccounts.stopIo()
+                UserDefaults.setMainAppRunning(false)
 
                 // to avoid 0xdead10cc exceptions, scheduled jobs need to be done before we get suspended;
                 // we increase the probabilty that this happens by waiting a moment before calling unregisterBackgroundTask()
@@ -424,8 +439,8 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
     private func performFetch(completionHandler: ((UIBackgroundFetchResult) -> Void)? = nil) {
         // `didReceiveRemoteNotification` as well as `performFetchWithCompletionHandler` might be called if we're in foreground,
         // in this case, there is no need to wait for things or do sth.
-        if appIsInForeground() {
-            logger.info("➡️ app already in foreground")
+        if appIsInForeground() || UserDefaults.nseFetching {
+            logger.info("➡️ app already in foreground or NSE running")
             pushToDebugArray("OK1")
             completionHandler?(.newData)
             return