fix: ios skip posting hash response after detached from engine (#22695)

* skip posting message after detached from engine

* review changes

* cancel plugin before destroying engine

---------

Co-authored-by: shenlong-tanwen <139912620+shalong-tanwen@users.noreply.github.com>
Co-authored-by: Alex <alex.tran1502@gmail.com>

mobile/ios/Runner/AppDelegate.swift

@@ -20,7 +20,7 @@ import UIKit
 
     GeneratedPluginRegistrant.register(with: self)
     let controller: FlutterViewController = window?.rootViewController as! FlutterViewController
-    AppDelegate.registerPlugins(binaryMessenger: controller.binaryMessenger)
+    AppDelegate.registerPlugins(with: controller.engine)
     BackgroundServicePlugin.register(with: self.registrar(forPlugin: "BackgroundServicePlugin")!)
 
     BackgroundServicePlugin.registerBackgroundProcessing()
@@ -51,9 +51,13 @@ import UIKit
     return super.application(application, didFinishLaunchingWithOptions: launchOptions)
   }
   
-  public static func registerPlugins(binaryMessenger: FlutterBinaryMessenger) {
-    NativeSyncApiSetup.setUp(binaryMessenger: binaryMessenger, api: NativeSyncApiImpl())
-    ThumbnailApiSetup.setUp(binaryMessenger: binaryMessenger, api: ThumbnailApiImpl())
-    BackgroundWorkerFgHostApiSetup.setUp(binaryMessenger: binaryMessenger, api: BackgroundWorkerApiImpl())
+  public static func registerPlugins(with engine: FlutterEngine) {
+    NativeSyncApiImpl.register(with: engine.registrar(forPlugin: NativeSyncApiImpl.name)!)
+    ThumbnailApiSetup.setUp(binaryMessenger: engine.binaryMessenger, api: ThumbnailApiImpl())
+    BackgroundWorkerFgHostApiSetup.setUp(binaryMessenger: engine.binaryMessenger, api: BackgroundWorkerApiImpl())
+  }
+  
+  public static func cancelPlugins(with engine: FlutterEngine) {
+    (engine.valuePublished(byPlugin: NativeSyncApiImpl.name) as? NativeSyncApiImpl)?.detachFromEngine()
   }
 }

mobile/ios/Runner/Background/BackgroundWorker.swift

@@ -95,7 +95,7 @@ class BackgroundWorker: BackgroundWorkerBgHostApi {
     // Register plugins in the new engine
     GeneratedPluginRegistrant.register(with: engine)
     // Register custom plugins
-    AppDelegate.registerPlugins(binaryMessenger: engine.binaryMessenger)
+    AppDelegate.registerPlugins(with: engine)
     flutterApi = BackgroundWorkerFlutterApi(binaryMessenger: engine.binaryMessenger)
     BackgroundWorkerBgHostApiSetup.setUp(binaryMessenger: engine.binaryMessenger, api: self)
     
@@ -168,6 +168,7 @@ class BackgroundWorker: BackgroundWorkerBgHostApi {
     }
     
     isComplete = true
+    AppDelegate.cancelPlugins(with: engine)
     engine.destroyContext()
     flutterApi = nil
     completionHandler(success)

mobile/ios/Runner/Core/ImmichPlugin.swift

@@ -0,0 +1,17 @@
+class ImmichPlugin: NSObject {
+  var detached: Bool
+  
+  override init() {
+    detached = false
+    super.init()
+  }
+  
+  func detachFromEngine() {
+    self.detached = true
+  }
+  
+  func completeWhenActive<T>(for completion: @escaping (T) -> Void, with value: T) {
+    guard !self.detached else { return }
+    completion(value)
+  }
+}

mobile/ios/Runner/Sync/MessagesImpl.swift

@@ -17,13 +17,25 @@ struct AssetWrapper: Hashable, Equatable {
   }
 }
 
-class NativeSyncApiImpl: NativeSyncApi {
+class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
+  static let name = "NativeSyncApi"
+  
+  static func register(with registrar: any FlutterPluginRegistrar) {
+    let instance = NativeSyncApiImpl()
+    NativeSyncApiSetup.setUp(binaryMessenger: registrar.messenger(), api: instance)
+    registrar.publish(instance)
+  }
+  
+  func detachFromEngine(for registrar: any FlutterPluginRegistrar) {
+    super.detachFromEngine()
+  }
+  
   private let defaults: UserDefaults
   private let changeTokenKey = "immich:changeToken"
   private let albumTypes: [PHAssetCollectionType] = [.album, .smartAlbum]
   private let recoveredAlbumSubType = 1000000219
   
-  private var hashTask: Task<Void, Error>?
+  private var hashTask: Task<Void?, Error>?
   private static let hashCancelledCode = "HASH_CANCELLED"
   private static let hashCancelled = Result<[HashResult], Error>.failure(PigeonError(code: hashCancelledCode, message: "Hashing cancelled", details: nil))
   
@@ -272,7 +284,7 @@ class NativeSyncApiImpl: NativeSyncApi {
       }
       
       if Task.isCancelled {
-        return completion(Self.hashCancelled)
+        return self?.completeWhenActive(for: completion, with: Self.hashCancelled)
       }
       
       await withTaskGroup(of: HashResult?.self) { taskGroup in
@@ -280,7 +292,7 @@ class NativeSyncApiImpl: NativeSyncApi {
         results.reserveCapacity(assets.count)
         for asset in assets {
           if Task.isCancelled {
-            return completion(Self.hashCancelled)
+            return self?.completeWhenActive(for: completion, with: Self.hashCancelled)
           }
           taskGroup.addTask {
             guard let self = self else { return nil }
@@ -290,7 +302,7 @@ class NativeSyncApiImpl: NativeSyncApi {
         
         for await result in taskGroup {
           guard let result = result else {
-            return completion(Self.hashCancelled)
+            return self?.completeWhenActive(for: completion, with: Self.hashCancelled)
           }
           results.append(result)
         }
@@ -299,7 +311,7 @@ class NativeSyncApiImpl: NativeSyncApi {
           results.append(HashResult(assetId: missing, error: "Asset not found in library", hash: nil))
         }
         
-        completion(.success(results))
+        return self?.completeWhenActive(for: completion, with: .success(results))
       }
     }
   }