Swift 6 migration for NSE (#5608)

* swift 6 support for NSE and concurrency safe implementations for it

* enforcing required Sendable conformance for swift 6 migration in NSE

* use Mutex to access the string builder cache

* use an async stream to update timeline items diffs

* fix for Sendable appHooks

ElementX.xcodeproj/project.pbxproj

@@ -906,7 +906,6 @@
 		94D9172C4B91FC6971C668CE /* LeaveSpaceView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0AE4B7AD74E402BBC46A801A /* LeaveSpaceView.swift */; };
 		94E15D018D70563FA4AB4E5A /* ComposerToolbarModels.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4D3A7375AB22721C436EB056 /* ComposerToolbarModels.swift */; };
 		94EB81606839C175CA6C2ADB /* RoomScreenTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D97A4E73EA97CA08D2BB9806 /* RoomScreenTests.swift */; };
-		94F0B78928E952689ACDB271 /* NetworkMonitor.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1D67E616BCA82D8A1258D488 /* NetworkMonitor.swift */; };
 		95690DDD9D547D3D842ACBE3 /* AnalyticsSettingsScreenCoordinator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4BD371B60E07A5324B9507EF /* AnalyticsSettingsScreenCoordinator.swift */; };
 		9586E90A447C4896C0CA3A8E /* TimelineItemReplyDetails.swift in Sources */ = {isa = PBXBuildFile; fileRef = BE89A8BD65CCE3FCC925CA14 /* TimelineItemReplyDetails.swift */; };
 		95B690EA99A3385D4B8A593D /* NotificationToneManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = B94A6A57FE7E71F7605070AA /* NotificationToneManager.swift */; };
@@ -1448,7 +1447,6 @@
 		F18CA61A58C77C84F551B8E7 /* GeneratedMocks.swift in Sources */ = {isa = PBXBuildFile; fileRef = 57916A1578D8043BB0795441 /* GeneratedMocks.swift */; };
 		F1C68F64FC8A66B6B9510BF7 /* ManageRoomMemberSheetView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1B30CD19ED6243FEDFBA8400 /* ManageRoomMemberSheetView.swift */; };
 		F252C0EA49088801F4CA6006 /* landscape_test_image.jpg in Resources */ = {isa = PBXBuildFile; fileRef = 96CE9D6642DD487D8CC90C9C /* landscape_test_image.jpg */; };
-		F253AAB4C8F06208173C9C4A /* Assets.swift in Sources */ = {isa = PBXBuildFile; fileRef = 71D52BAA5BADB06E5E8C295D /* Assets.swift */; };
 		F255083E18CDBFDF7E640FB1 /* Avatars.swift in Sources */ = {isa = PBXBuildFile; fileRef = C142248014E08E885E323E56 /* Avatars.swift */; };
 		F2D5C0E1351DA7BD16867629 /* TimelineStyle.swift in Sources */ = {isa = PBXBuildFile; fileRef = 6CD4823EAB4B4E8BAB4F6B8C /* TimelineStyle.swift */; };
 		F2E580C0FBFBEFFE9D69893B /* RoomPreviewProxyProtocol.swift in Sources */ = {isa = PBXBuildFile; fileRef = 739077686814E4EA339B1C83 /* RoomPreviewProxyProtocol.swift */; };
@@ -7796,7 +7794,6 @@
 				68C3AF257678F6E7BB238C3F /* AppAppearance.swift in Sources */,
 				A2172B5A26976F9174228B8A /* AppHooks.swift in Sources */,
 				E1DE8A5422643F759385290F /* AppSettings.swift in Sources */,
-				F253AAB4C8F06208173C9C4A /* Assets.swift in Sources */,
 				484202C5D50983442D24D061 /* AttributedString.swift in Sources */,
 				CDCA8A559E098503DDE29477 /* AttributedStringBuilder.swift in Sources */,
 				BA43D782BE85C7F5F20C624A /* AttributedStringBuilderProtocol.swift in Sources */,
@@ -7835,7 +7832,6 @@
 				E2DB696117BAEABAD5718023 /* MediaSourceProxy.swift in Sources */,
 				4CB30D9BD72CA3FEEFAA0793 /* NSEUserSession.swift in Sources */,
 				1D5DC685CED904386C89B7DA /* NSRegularExpresion.swift in Sources */,
-				94F0B78928E952689ACDB271 /* NetworkMonitor.swift in Sources */,
 				4DEEFB73181C3B023DB42686 /* NetworkMonitorProtocol.swift in Sources */,
 				5C02841B2A86327B2C377682 /* NotificationConstants.swift in Sources */,
 				2689D22EF1D10D22B0A4DAEA /* NotificationContentBuilder.swift in Sources */,
@@ -9545,7 +9541,9 @@
 				PRODUCT_DISPLAY_NAME = "$(APP_DISPLAY_NAME)";
 				PRODUCT_NAME = NSE;
 				SDKROOT = iphoneos;
+				SWIFT_APPROACHABLE_CONCURRENCY = YES;
 				SWIFT_OBJC_INTERFACE_HEADER_NAME = "GeneratedInterface-Swift.h";
+				SWIFT_VERSION = 6.2;
 				TARGETED_DEVICE_FAMILY = "1,2";
 			};
 			name = Release;
@@ -9926,7 +9924,9 @@
 				PRODUCT_DISPLAY_NAME = "$(APP_DISPLAY_NAME)";
 				PRODUCT_NAME = NSE;
 				SDKROOT = iphoneos;
+				SWIFT_APPROACHABLE_CONCURRENCY = YES;
 				SWIFT_OBJC_INTERFACE_HEADER_NAME = "GeneratedInterface-Swift.h";
+				SWIFT_VERSION = 6.2;
 				TARGETED_DEVICE_FAMILY = "1,2";
 			};
 			name = Debug;

ElementX/Sources/AppHooks/AppHooks.swift

@@ -7,66 +7,107 @@
 //
 
 import Foundation
+import Synchronization
 
-class AppHooks: AppHooksProtocol {
+final class AppHooks: AppHooksProtocol {
     #if IS_MAIN_APP
     func configure(with userSession: UserSessionProtocol?) async {
         await roomScreenHook.configure(with: userSession)
     }
     
-    private(set) var appSettingsHook: AppSettingsHookProtocol = DefaultAppSettingsHook()
+    private let _appSettingsHook: Mutex<AppSettingsHookProtocol> = Mutex(DefaultAppSettingsHook())
+    var appSettingsHook: AppSettingsHookProtocol {
+        _appSettingsHook.withLock { $0 }
+    }
+    
     func registerAppSettingsHook(_ hook: AppSettingsHookProtocol) {
-        appSettingsHook = hook
+        _appSettingsHook.withLock { $0 = hook }
+    }
+    
+    private let _compoundHook: Mutex<CompoundHookProtocol> = Mutex(DefaultCompoundHook())
+    var compoundHook: CompoundHookProtocol {
+        _compoundHook.withLock { $0 }
     }
 
-    private(set) var compoundHook: CompoundHookProtocol = DefaultCompoundHook()
     func registerCompoundHook(_ hook: CompoundHookProtocol) {
-        compoundHook = hook
+        _compoundHook.withLock { $0 = hook }
+    }
+    
+    private let _bugReportHook: Mutex<BugReportHookProtocol> = Mutex(DefaultBugReportHook())
+    var bugReportHook: BugReportHookProtocol {
+        _bugReportHook.withLock { $0 }
     }
     
-    private(set) var bugReportHook: BugReportHookProtocol = DefaultBugReportHook()
     func registerBugReportHook(_ hook: BugReportHookProtocol) {
-        bugReportHook = hook
+        _bugReportHook.withLock { $0 = hook }
+    }
+    
+    private let _certificateValidatorHook: Mutex<CertificateValidatorHookProtocol> = Mutex(DefaultCertificateValidator())
+    var certificateValidatorHook: CertificateValidatorHookProtocol {
+        _certificateValidatorHook.withLock { $0 }
     }
     
-    private(set) var certificateValidatorHook: CertificateValidatorHookProtocol = DefaultCertificateValidator()
     func registerCertificateValidatorHook(_ hook: CertificateValidatorHookProtocol) {
-        certificateValidatorHook = hook
+        _certificateValidatorHook.withLock { $0 = hook }
+    }
+    
+    private let _oAuthPresenterHook: Mutex<OAuthPresenterHookProtocol> = Mutex(DefaultOAuthPresenterHook())
+    var oAuthPresenterHook: OAuthPresenterHookProtocol {
+        _oAuthPresenterHook.withLock { $0 }
     }
     
-    private(set) var oAuthPresenterHook: OAuthPresenterHookProtocol = DefaultOAuthPresenterHook()
     func registerOAuthPresenterHook(_ hook: OAuthPresenterHookProtocol) {
-        oAuthPresenterHook = hook
+        _oAuthPresenterHook.withLock { $0 = hook }
+    }
+    
+    private let _roomScreenHook: Mutex<RoomScreenHookProtocol> = Mutex(DefaultRoomScreenHook())
+    var roomScreenHook: RoomScreenHookProtocol {
+        _roomScreenHook.withLock { $0 }
     }
     
-    private(set) var roomScreenHook: RoomScreenHookProtocol = DefaultRoomScreenHook()
     func registerRoomScreenHook(_ hook: RoomScreenHookProtocol) {
-        roomScreenHook = hook
+        _roomScreenHook.withLock { $0 = hook }
+    }
+    
+    private let _developerOptionsScreenHook: Mutex<DeveloperOptionsScreenHookProtocol> = Mutex(DefaultDeveloperOptionsScreenHook())
+    var developerOptionsScreenHook: DeveloperOptionsScreenHookProtocol {
+        _developerOptionsScreenHook.withLock { $0 }
     }
     
-    private(set) var developerOptionsScreenHook: DeveloperOptionsScreenHookProtocol = DefaultDeveloperOptionsScreenHook()
     func registerDeveloperOptionsScreenHook(_ hook: DeveloperOptionsScreenHookProtocol) {
-        developerOptionsScreenHook = hook
+        _developerOptionsScreenHook.withLock { $0 = hook }
     }
     #endif
     
-    private(set) var tracingHook: TracingHookProtocol = DefaultTracingHook()
+    private let _tracingHook: Mutex<TracingHookProtocol> = Mutex(DefaultTracingHook())
+    var tracingHook: TracingHookProtocol {
+        _tracingHook.withLock { $0 }
+    }
+    
     func registerTracingHook(_ hook: TracingHookProtocol) {
-        tracingHook = hook
+        _tracingHook.withLock { $0 = hook }
+    }
+    
+    private let _clientBuilderHook: Mutex<ClientBuilderHookProtocol> = Mutex(DefaultClientBuilderHook())
+    var clientBuilderHook: ClientBuilderHookProtocol {
+        _clientBuilderHook.withLock { $0 }
     }
     
-    private(set) var clientBuilderHook: ClientBuilderHookProtocol = DefaultClientBuilderHook()
     func registerClientBuilderHook(_ hook: ClientBuilderHookProtocol) {
-        clientBuilderHook = hook
+        _clientBuilderHook.withLock { $0 = hook }
+    }
+    
+    private let _remoteSettingsHook: Mutex<RemoteSettingsHookProtocol> = Mutex(DefaultRemoteSettingsHook())
+    var remoteSettingsHook: RemoteSettingsHookProtocol {
+        _remoteSettingsHook.withLock { $0 }
     }
     
-    private(set) var remoteSettingsHook: RemoteSettingsHookProtocol = DefaultRemoteSettingsHook()
     func registerRemoteSettingsHook(_ hook: RemoteSettingsHookProtocol) {
-        remoteSettingsHook = hook
+        _remoteSettingsHook.withLock { $0 = hook }
     }
 }
 
-protocol AppHooksProtocol {
+protocol AppHooksProtocol: Sendable {
     func setUp()
 }
 

ElementX/Sources/AppHooks/Hooks/ClientBuilderHook.swift

@@ -8,7 +8,7 @@
 
 import MatrixRustSDK
 
-protocol ClientBuilderHookProtocol {
+protocol ClientBuilderHookProtocol: Sendable {
     func configure(_ builder: ClientBuilder) -> ClientBuilder
 }
 

ElementX/Sources/AppHooks/Hooks/RemoteSettingsHook.swift

@@ -13,7 +13,7 @@ enum RemoteSettingsError: Error {
     case elementProRequired(serverName: String)
 }
 
-protocol RemoteSettingsHookProtocol {
+protocol RemoteSettingsHookProtocol: Sendable {
     #if IS_MAIN_APP
     @MainActor func initializeCache(using client: ClientProtocol, applyingTo appSettings: CommonSettingsProtocol) async -> Result<Void, RemoteSettingsError>
     func updateCache(using client: ClientProtocol) async

ElementX/Sources/AppHooks/Hooks/TracingHook.swift

@@ -8,7 +8,7 @@
 
 import MatrixRustSDK
 
-protocol TracingHookProtocol {
+protocol TracingHookProtocol: Sendable {
     func update(_ configuration: TracingConfiguration, with rageshakeURL: RemotePreference<RageshakeConfiguration>)
 }
 

ElementX/Sources/Application/Settings/AppSettings.swift

@@ -14,7 +14,7 @@ import Foundation
 import SwiftUI
 
 /// Common settings between app and NSE
-protocol CommonSettingsProtocol: AnyObject {
+protocol CommonSettingsProtocol: AnyObject, Sendable {
     var lastNotificationBootTime: TimeInterval? { get set }
     var selectedNotificationTone: NotificationTone? { get set }
 
@@ -34,7 +34,9 @@ enum AppBuildType {
 }
 
 /// Store Element specific app settings.
-final class AppSettings {
+///
+/// State is persisted in `UserDefaults`, which is thread-safe per Apple's documentation, hence `@unchecked`.
+final class AppSettings: @unchecked Sendable {
     private enum UserDefaultsKeys: String {
         case lastVersionLaunched
         case seenInvites
@@ -92,10 +94,10 @@ final class AppSettings {
         case developerOptionsEnabled
     }
     
-    private static var suiteName: String = InfoPlistReader.main.appGroupIdentifier
+    private nonisolated(unsafe) static var suiteName: String = InfoPlistReader.main.appGroupIdentifier
 
-    /// UserDefaults to be used on reads and writes.
+    /// UserDefaults to be used on reads and writes. `UserDefaults` is thread-safe per Apple's documentation.
-    private static var store: UserDefaults! = UserDefaults(suiteName: suiteName)
+    private nonisolated(unsafe) static var store: UserDefaults! = UserDefaults(suiteName: suiteName)
     
     static var appBuildType: AppBuildType {
         #if DEBUG

ElementX/Sources/Other/CurrentValuePublisher.swift

@@ -10,7 +10,9 @@ import Combine
 
 /// A wrapper of CurrentValueSubject.
 /// The purpose of this type is to remove the possibility to send new values on the underlying subject.
-struct CurrentValuePublisher<Output, Failure: Error>: Publisher {
+///
+/// `CurrentValueSubject` is documented as thread-safe but is not formally `Sendable`, hence `@unchecked`.
+struct CurrentValuePublisher<Output, Failure: Error>: Publisher, @unchecked Sendable {
     private let subject: CurrentValueSubject<Output, Failure>
     
     init(_ subject: CurrentValueSubject<Output, Failure>) {

ElementX/Sources/Other/ExpiringTaskRunner.swift

@@ -15,9 +15,9 @@ enum ExpiringTaskRunnerError: Error {
 actor ExpiringTaskRunner<T: Sendable> {
     private var continuation: CheckedContinuation<T, Error>?
     
-    private var task: () async throws -> T
+    private var task: @Sendable () async throws -> T
 
-    init(_ task: @escaping () async throws -> T) {
+    init(_ task: @escaping @Sendable () async throws -> T) {
         self.task = task
     }
     

ElementX/Sources/Other/Extensions/Bundle.swift

@@ -7,6 +7,7 @@
 //
 
 import Foundation
+import Synchronization
 
 public extension Bundle {
     /// The top-level bundle that contains the entire app.
@@ -24,11 +25,11 @@ public extension Bundle {
     
     // MARK: - Localisation
     
-    /// Overrides `Bundle.app.preferredLocalizations` for testing translations.
+    /// Overrides `Bundle.app.preferredLocalizations` for testing translations since this is
-    static var overrideLocalizations: [String]?
+    /// only for testing, and is changed at runtime only in tests, it's fine to keep as `nonisolated(unsafe)`
+    nonisolated(unsafe) static var overrideLocalizations: [String]?
 
-    private static let cacheDispatchQueue = DispatchQueue(label: "io.element.elementx.localization_bundle_cache")
+    private static let cachedBundles = Mutex<[String: Bundle]>([:])
-    private static var cachedBundles = [String: Bundle]()
 
     /// Get an lproj language bundle from the receiver bundle.
     /// - Parameter language: The language to try to load.
@@ -52,17 +53,10 @@ public extension Bundle {
     // MARK: - Private
 
     private static func cacheValue(_ value: Bundle?, forKey key: String) {
-        cacheDispatchQueue.sync {
+        cachedBundles.withLock { $0[key] = value }
-            cachedBundles[key] = value
-        }
     }
 
     private static func cachedValue(forKey key: String) -> Bundle? {
-        var result: Bundle?
+        cachedBundles.withLock { $0[key] }
-        cacheDispatchQueue.sync {
-            result = cachedBundles[key]
-        }
-        
-        return result
     }
 }

ElementX/Sources/Other/HTMLParsing/AttributedStringBuilder.swift

@@ -10,6 +10,7 @@ import Compound
 import LRUCache
 import MatrixRustSDK
 import SwiftSoup
+import Synchronization
 import UIKit
 
 protocol MentionBuilderProtocol {
@@ -42,11 +43,10 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
     private let mentionBuilder: MentionBuilderProtocol
     
     private static let attributeMSC4286 = "msc4286-external-payment-details"
-    private static let cacheDispatchQueue = DispatchQueue(label: "io.element.elementx.attributed_string_builder_v2_cache")
+    private static let caches = Mutex<[String: LRUCache<String, AttributedString>]>([:])
-    private static var caches: [String: LRUCache<String, AttributedString>] = [:]
 
     static func invalidateCaches() {
-        caches.removeAll()
+        caches.withLock { $0.removeAll() }
     }
     
     init(cacheKey: String = defaultKey, mentionBuilder: MentionBuilderProtocol) {
@@ -279,7 +279,7 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
     }
     
     private static func cacheValue(_ value: AttributedString?, forKey key: String, cacheKey: String) {
-        cacheDispatchQueue.sync {
+        caches.withLock { caches in
             if caches[cacheKey] == nil {
                 caches[cacheKey] = LRUCache<String, AttributedString>(countLimit: 1000)
             }
@@ -289,12 +289,7 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
     }
 
     private static func cachedValue(forKey key: String, cacheKey: String) -> AttributedString? {
-        var result: AttributedString?
+        caches.withLock { $0[cacheKey]?.value(forKey: key) }
-        cacheDispatchQueue.sync {
-            result = caches[cacheKey]?.value(forKey: key)
-        }
-        
-        return result
     }
     
     // swiftlint:disable:next cyclomatic_complexity

ElementX/Sources/Other/Logging/Tracing.swift

@@ -22,7 +22,7 @@ enum Tracing {
     /// Set this to temporarily override the directory from which logs will be collected.
     /// This basically only affects ``logFiles``, and doesn't inform the SDK to write
     /// the logs to a different directory, which should be done before setting this.
-    static var logsDirectoryOverride: URL?
+    nonisolated(unsafe) static var logsDirectoryOverride: URL?
     static var legacyLogsDirectory: URL {
         .appGroupContainerDirectory
     }

ElementX/Sources/Other/SDKListener.swift

@@ -13,12 +13,12 @@ import MatrixRustSDK
 ///
 /// To use this you'll need to add a conformance to the required listener
 /// protocol with a specialisation for the type it listens for.
-final class SDKListener<T> {
+final class SDKListener<T>: Sendable {
-    private let onUpdateClosure: (T) -> Void
+    private let onUpdateClosure: @Sendable (T) -> Void
 
     /// Creates a new listener.
     /// - Parameter onUpdateClosure: A closure that will be called whenever a new value is available.
-    init(_ onUpdateClosure: @escaping (T) -> Void) {
+    init(_ onUpdateClosure: @escaping @Sendable (T) -> Void) {
         self.onUpdateClosure = onUpdateClosure
     }
 }

ElementX/Sources/Services/Media/Provider/MediaLoaderProtocol.swift

@@ -16,7 +16,7 @@ enum MediaLoaderError: Error {
 }
 
 // sourcery: AutoMockable
-protocol MediaLoaderProtocol {
+protocol MediaLoaderProtocol: Sendable {
     func loadMediaContentForSource(_ source: MediaSourceProxy) async throws -> Data
 
     func loadMediaThumbnailForSource(_ source: MediaSourceProxy, width: UInt, height: UInt) async throws -> Data

ElementX/Sources/Services/Notification/Manager/NotificationManager.swift

@@ -159,7 +159,7 @@ final class NotificationManager: NSObject, NotificationManagerProtocol {
     }
     
     private func removeReceivedWhileOfflineNotification() {
-        notificationCenter.removeDeliveredNotifications(withIdentifiers: [NotificationServiceExtension.receivedWhileOfflineNotificationID])
+        notificationCenter.removeDeliveredNotifications(withIdentifiers: [NotificationServiceExtensionActor.receivedWhileOfflineNotificationID])
     }
 
     private func setPusher(with deviceToken: Data, clientProxy: ClientProxyProtocol) async -> Bool {

ElementX/Sources/Services/Timeline/TimelineItemProvider.swift

@@ -12,10 +12,14 @@ import MatrixRustSDK
 
 class TimelineItemProvider: TimelineItemProviderProtocol {
     private var cancellables = Set<AnyCancellable>()
-    private let serialDispatchQueue: DispatchQueue
 
     private var roomTimelineObservationToken: TaskHandle?
 
+    /// Bridge from the SDK's synchronous callback into Swift Concurrency. Yielding is safe from any
+    /// thread; a single long-lived `for await` consumer (set up in `init`) applies the diffs on the
+    /// main actor in FIFO order, guaranteeing one in-flight update at a time.
+    private let diffContinuation: AsyncStream<[TimelineDiff]>.Continuation
+
     private let paginationStateSubject = CurrentValueSubject<TimelinePaginationState, Never>(.initial)
     var paginationState: TimelinePaginationState {
         paginationStateSubject.value
@@ -43,25 +47,34 @@ class TimelineItemProvider: TimelineItemProviderProtocol {
     }
 
     deinit {
+        diffContinuation.finish()
         roomTimelineObservationToken?.cancel()
     }
 
     init(timeline: Timeline, kind: TimelineKind, paginationStatePublisher: AnyPublisher<TimelinePaginationState, Never>) {
-        serialDispatchQueue = DispatchQueue(label: "io.element.elementx.timeline_item_provider", qos: .utility)
         itemProxiesSubject = CurrentValueSubject<[TimelineItemProxy], Never>([])
         self.kind = kind
 
+        let (diffStream, diffContinuation) = AsyncStream<[TimelineDiff]>.makeStream()
+        self.diffContinuation = diffContinuation
+
         paginationStatePublisher
             .sink { [weak self] in
                 self?.paginationStateSubject.send($0)
             }
             .store(in: &cancellables)
 
-        Task {
+        // `for await` guarantees FIFO ordering and that only one diff is being applied at a time.
-            roomTimelineObservationToken = await timeline.addListener(listener: SDKListener { [weak self] timelineDiffs in
+        // The stream also allows to handle the sendable items in the listener.
-                self?.serialDispatchQueue.sync {
+        Task { [weak self] in
-                    self?.updateItemsWithDiffs(timelineDiffs)
+            for await diffs in diffStream {
+                self?.updateItemsWithDiffs(diffs)
             }
+        }
+
+        Task {
+            roomTimelineObservationToken = await timeline.addListener(listener: SDKListener { diffs in
+                diffContinuation.yield(diffs)
             })
         }
     }

NSE/Sources/NotificationContentBuilder.swift

@@ -250,7 +250,7 @@ struct NotificationContentBuilder {
 
         if let fetchedImage {
             image = fetchedImage
-        } else if let data = await getPlaceholderAvatarImageData(name: icon.groupInfo?.avatarDisplayName ?? senderAvatarDisplayName,
+        } else if let data = await Self.getPlaceholderAvatarImageData(name: icon.groupInfo?.avatarDisplayName ?? senderAvatarDisplayName,
                                                                       id: icon.groupInfo?.id ?? senderID) {
             image = INImage(imageData: data)
         } else {
@@ -309,7 +309,7 @@ struct NotificationContentBuilder {
     }
 
     @MainActor
-    func getPlaceholderAvatarImageData(name: String, id: String) async -> Data? {
+    static func getPlaceholderAvatarImageData(name: String, id: String) async -> Data? {
         // The version value is used in case the design of the placeholder is updated to force a replacement
         let prefix = "notification_placeholderV9"
         

NSE/Sources/NotificationHandler.swift

@@ -8,6 +8,7 @@
 
 import CallKit
 import MatrixRustSDK
+import Synchronization
 import UserNotifications
 
 class NotificationHandler {
@@ -19,9 +20,6 @@ class NotificationHandler {
     
     private let notificationContentBuilder: NotificationContentBuilder
 
-    // periphery:ignore - required for instance retention in the rust codebase
-    private var roomInfoObservationToken: TaskHandle?
-    
     init(userSession: NSEUserSession,
          settings: CommonSettingsProtocol,
          contentHandler: @escaping (UNNotificationContent) -> Void,
@@ -184,9 +182,13 @@ class NotificationHandler {
         // Check to see if a call is still ongoing
         if let room = userSession.roomForIdentifier(roomID) { // Try to get call details from the room info
             if !room.hasActiveRoomCall() { // If I don't have an active call wait a bit and make sure
+                // Local `Mutex` holder for the SDK subscription token — keeps it alive across the
+                // await without needing `[weak self]`, which would force this class to be `Sendable`.
+                let observationToken = Mutex<TaskHandle?>(nil)
                 let expiringTask = ExpiringTaskRunner {
-                    await withCheckedContinuation { [weak self] continuation in
+                    await withCheckedContinuation { (continuation: CheckedContinuation<Void, Never>) in
-                        self?.roomInfoObservationToken = room.subscribeToRoomInfoUpdates(listener: SDKListener { info in
+                        observationToken.withLock { state in
+                            state = room.subscribeToRoomInfoUpdates(listener: SDKListener { info in
                                 if info.hasRoomCall {
                                     MXLog.info("Received room info update and the room has an active call now.")
                                     continuation.resume()
@@ -196,8 +198,11 @@ class NotificationHandler {
                             })
                         }
                     }
+                }
 
-                try? await expiringTask.run(timeout: .seconds(5)) // Wait 5 seconds or just use whatever is available
+                try? await expiringTask.run(timeout: Duration.seconds(5)) // Wait 5 seconds or just use whatever is available
+                // Release the SDK subscription explicitly once we no longer need updates.
+                observationToken.withLock { $0 = nil }
 
                 guard room.hasActiveRoomCall() else {
                     MXLog.info("The room no longer has an ongoing call, handling as push notification")

NSE/Sources/NotificationServiceExtension.swift

@@ -8,7 +8,8 @@
 
 import Combine
 import MatrixRustSDK
-import UserNotifications
+import Synchronization
+@preconcurrency import UserNotifications
 
 // The lifecycle of the NSE looks something like the following:
 //  1)  App receives notification
@@ -29,31 +30,55 @@ import UserNotifications
 // called on the same instance of `NotificationService` as a previous
 // notification.
 
-class NotificationServiceExtension: UNNotificationServiceExtension {
+final class NotificationServiceExtension: UNNotificationServiceExtension {
+    let actor: NotificationServiceExtensionActor
+    
+    override init() {
+        actor = NotificationServiceExtensionActor()
+        super.init()
+    }
+    
+    /// This wouldn't be allowed normally because we added `@Sendable` to the contentHandler which is not by default, however there's nothing we can do about it
+    /// since the `UNNotificationServiceExtension` does not support swift 6 concurency yet, so we need to use the `@preconcurrency import` to suppress
+    /// this error, and then we handle all the concurrency logic inside the actor that the NSE delegates all the logic to.
+    override func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping @Sendable (UNNotificationContent) -> Void) {
+        let actor = actor
+        Task { await actor.handle(request, withContentHandler: contentHandler) }
+    }
+    
+    override func serviceExtensionTimeWillExpire() {
+        actor.serviceExtensionTimeWillExpire()
+    }
+}
+
+actor NotificationServiceExtensionActor {
     static let receivedWhileOfflineNotificationID = "io.element.elementx.receivedWhileOfflineNotification"
 
-    private static var targetConfiguration: Target.ConfigurationResult?
+    /// Process-wide target configuration, `Mutex`-protected so it can be read/written from any
+    /// thread (in particular, from the actor's synchronous `init` without spawning a Task).
+    private static let targetConfiguration = Mutex<Target.ConfigurationResult?>(nil)
 
+    @MainActor
     private static var hasHandledFirstNotificationSinceBoot = false
+    
     private static let firstNotificationThreshold: TimeInterval = 15 * 60
     
     private let settings: CommonSettingsProtocol = AppSettings()
     private let appHooks: AppHooks
     
-    private var notificationHandler: NotificationHandler?
+    /// This is nonisolated just because the expire function needs to be served ASAP so we should not call it from  a Task, however this is
+    /// always written and read in the actor isolated context, and only read nonisolated in `serviceExtensionTimeWillExpire` function
+    /// which is an acceptable compromise since it's a failure state, and the race condition will not make it worse and present a partial notification regardless.
+    private nonisolated(unsafe) var notificationHandler: NotificationHandler?
     private let keychainController = KeychainController(service: .sessions,
                                                         accessGroup: InfoPlistReader.main.keychainAccessGroupIdentifier)
         
-    private var cancellables: Set<AnyCancellable> = []
-    
-    /// We can make the whole NSE a MainActor after https://github.com/swiftlang/swift-evolution/blob/main/proposals/0371-isolated-synchronous-deinit.md
-    /// otherwise we wouldn't be able to log the tag in the deinit.
     deinit {
         ExtensionLogger.logMemory(with: tag)
         MXLog.info("\(tag) deinit")
     }
     
-    override init() {
+    init() {
         appHooks = AppHooks()
         appHooks.setUp()
 
@@ -61,42 +86,40 @@ class NotificationServiceExtension: UNNotificationServiceExtension {
         // the target configuration will fail. We could call exit(0) here, however with the
         // notification filtering entitlement that results in the notification being discarded
         // so we need to wait for the delegate method to be called and bail out there instead.
-        if !BootDetectionManager.isDeviceLockedAfterReboot(containerURL: URL.appGroupContainerDirectory),
+        // The `Mutex` guarantees `Target.nse.configure(...)` runs at most once per process even
-           Self.targetConfiguration == nil {
+        // under concurrent NSE instance creation.
-            Self.targetConfiguration = Target.nse.configure(logLevel: settings.logLevel,
+        if !BootDetectionManager.isDeviceLockedAfterReboot(containerURL: URL.appGroupContainerDirectory) {
+            Self.targetConfiguration.withLock { state in
+                guard state == nil else { return }
+                state = Target.nse.configure(logLevel: settings.logLevel,
                                              traceLogPacks: settings.traceLogPacks,
                                              sentryURL: nil,
                                              rageshakeURL: settings.bugReportRageshakeURL,
                                              appHooks: appHooks)
             }
-        
+        }
-        super.init()
     }
     
-    override func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {
+    func handle(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) async {
-        Task { await handle(request, withContentHandler: contentHandler) }
-    }
-    
-    private func handle(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) async {
         // If we skipped configuring the target it means we can't write to the app group, so we're unlikely to
         // be able to create a session (and even if we could, we would be missing the lightweightTokioRuntime).
         // Additionally, APNs servers only store the most recent notification when the device is powered off.
         // So lets a) skip processing the notification and b) deliver a special "offline" notification as a workaround.
-        guard Self.targetConfiguration != nil else {
+        guard Self.targetConfiguration.withLock({ $0 != nil }) else {
             // MXLog isn't configured:
             // swiftlint:disable:next print_deprecation
             print("Device is locked after reboot.")
             
-            if Self.hasHandledFirstNotificationSinceBoot {
+            if await Self.hasHandledFirstNotificationSinceBoot {
                 return contentHandler(request.content)
             } else {
-                Self.hasHandledFirstNotificationSinceBoot = true
+                await MainActor.run { Self.hasHandledFirstNotificationSinceBoot = true }
                 deliverReceivedWhileOfflineNotification(for: request)
                 return contentHandler(.init())
             }
         }
         
-        guard !shouldDeliverReceivedWhileOfflineNotification() else {
+        guard await !shouldDeliverReceivedWhileOfflineNotification() else {
             // Don't log until the app hooks have been run:
             // swiftlint:disable:next print_deprecation
             print("Device is unlocked but may have missed notifications while offline.")
@@ -167,7 +190,7 @@ class NotificationServiceExtension: UNNotificationServiceExtension {
         }
     }
     
-    override func serviceExtensionTimeWillExpire() {
+    nonisolated func serviceExtensionTimeWillExpire() {
         notificationHandler?.handleTimeExpiration()
     }
     
@@ -180,13 +203,13 @@ class NotificationServiceExtension: UNNotificationServiceExtension {
     ///
     /// Note that this only handles the first-boot case. When the SDK is able to compute the unread count, we should start to use the NSE,
     /// remote-notifications (content-available) and background app refreshes to fetch and deliver our notifications as a more robust solution.
-    private func shouldDeliverReceivedWhileOfflineNotification() -> Bool {
+    private func shouldDeliverReceivedWhileOfflineNotification() async -> Bool {
-        if Self.hasHandledFirstNotificationSinceBoot {
+        if await Self.hasHandledFirstNotificationSinceBoot {
             // If we've already handled the first notification in this process there's no need to continue.
             return false
         }
         
-        Self.hasHandledFirstNotificationSinceBoot = true
+        await MainActor.run { Self.hasHandledFirstNotificationSinceBoot = true }
         
         guard let currentBootTime = BootDetectionManager.systemBootTime() else {
             // There's not much we can do if the boot time is unknown, so don't show the offline notification.
@@ -239,7 +262,7 @@ class NotificationServiceExtension: UNNotificationServiceExtension {
     
     // MARK: - Logging
 
-    private var tag: String {
+    private nonisolated var tag: String {
         "[NSE][\(Unmanaged.passUnretained(self).toOpaque())][\(Unmanaged.passUnretained(Thread.current).toOpaque())][\(ProcessInfo.processInfo.processIdentifier)]"
     }
 }

NSE/SupportingFiles/target.yml

@@ -74,6 +74,8 @@ targets:
         CURRENT_PROJECT_VERSION: $(CURRENT_PROJECT_VERSION)
         DEVELOPMENT_TEAM: $(DEVELOPMENT_TEAM)
         SWIFT_OBJC_INTERFACE_HEADER_NAME: GeneratedInterface-Swift.h
+        SWIFT_VERSION: 6.2
+        SWIFT_APPROACHABLE_CONCURRENCY: YES
         OTHER_SWIFT_FLAGS:
         - "-DIS_NSE"
 
@@ -87,7 +89,6 @@ targets:
     - path: ../../Secrets/Secrets.swift
     - path: ../../ElementX/Sources/Application/Settings
     - path: ../../ElementX/Sources/Application/TargetConfiguration.swift
-    - path: ../../ElementX/Sources/Generated/Assets.swift
     - path: ../../ElementX/Sources/Generated/Strings.swift
     - path: ../../ElementX/Sources/Other/Avatars.swift
     - path: ../../ElementX/Sources/Other/CurrentValuePublisher.swift
@@ -111,7 +112,7 @@ targets:
     - path: ../../ElementX/Sources/Other/InfoPlistReader.swift
     - path: ../../ElementX/Sources/Other/Logging
     - path: ../../ElementX/Sources/Other/MatrixEntityRegex.swift
-    - path: ../../ElementX/Sources/Other/NetworkMonitor
+    - path: ../../ElementX/Sources/Other/NetworkMonitor/NetworkMonitorProtocol.swift
     - path: ../../ElementX/Sources/Other/Pills/PillUtilities.swift
     - path: ../../ElementX/Sources/Other/Pills/PlainMentionBuilder.swift
     - path: ../../ElementX/Sources/Other/SDKListener.swift