Swift 6: complete concurrency checking #825

laevandus · 2025-05-07T12:08:11Z

🔗 Issue Links

Resolves: IOS-736

🎯 Goal

Set Swift version to 6 and implement complete concurrency checking

📝 Summary

Set Swift version to 6 in StreamChatSwiftUI and demo app (includes SWIFT_STRICT_CONCURRENCY = complete)
Add Sendable conformance to many types
Many protocols and types related to UI get @preconcurrency @MainActor requirement (e.g. view models)
Use MainActor.ensureIsolated for jumping on the main actor from controller delegates and completion handlers
Upgrade Nuke to version 12.8 (otherwise we can't compile with complete concurrency checking)
- LazyImage has breaking changes in Nuke (more testing for image scaling and gifs is needed)
Patch SwiftyGif for supporting complete concurrency checking (not beautiful)

🛠 Implementation

🎨 Showcase

🧪 Manual Testing Notes

Full manual regression testing round is needed.

☑️ Contributor Checklist

I have signed the Stream CLA (required)
This change should be manually QAed
Changelog is updated with client-facing changes
Changelog is updated with new localization keys
New code is covered by unit tests
Documentation has been updated in the docs-content repo

# Conflicts: # StreamChatSwiftUI.xcodeproj/project.pbxproj

… and completions

github-actions · 2025-05-07T12:20:30Z

	1 Warning
⚠️	Big PR

	1 Message
📖	There seems to be app changes but CHANGELOG wasn't modified. Please include an entry if the PR includes user-facing changes. You can find it at CHANGELOG.md.

Generated by 🚫 Danger

laevandus · 2025-05-07T12:51:37Z

Scripts/removePublicDeclarations.sh

-		replaceDeclaration ' Image?' ' NukeImage?' $f
-		replaceDeclaration ' Image(' ' NukeImage(' $f
-		replaceDeclaration 'struct Image:' 'struct NukeImage:' $f
-		replaceDeclaration 'extension Image {' 'extension NukeImage {' $f
-		replaceDeclaration 'Content == Image' 'Content == NukeImage' $f


Nuke was upgraded to 12.8 (supports Swift 6), some of the types are not there anymore

laevandus · 2025-05-07T13:02:49Z

Sources/StreamChatSwiftUI/Appearance.swift

-    static var `default`: Appearance = .init()
+    nonisolated(unsafe) static var `default`: Appearance = .init()


Appearance is a class in SwiftUI and its properties are accessible through InjectedValues.
@injected makes it impossible top make the Appearance itself @MainActor because @Injected(\.images) private var images can't ensure main actor isolation when a type/view X is created.
The other option would be to use a lock within Appearance to make sure everything is concurrency safe, but that feels like too much because the type itself is called from main anyway (if not mistakenly calling from background threads).

laevandus · 2025-05-08T07:12:13Z

.github/workflows/smoke-checks.yml

@@ -66,7 +66,8 @@ jobs:
  build-xcode15:
    name: Build SDKs (Xcode 15)
    runs-on: macos-15
-    if: ${{ github.event.inputs.record_snapshots != 'true' }}
+    #if: ${{ github.event.inputs.record_snapshots != 'true' }}
+    if: false


Xcode 15 builds are going away, disabling it for now and a cleanup happens separately

laevandus · 2025-05-08T07:13:29Z

Sources/StreamChatSwiftUI/Appearance.swift

+    nonisolated(unsafe)
+    public static var localizationProvider: @Sendable(_ key: String, _ table: String) -> String = { key, table in
        Bundle.streamChatUI.localizedString(forKey: key, value: nil, table: table)
    }


Alternative could be making it @MainActor instead of opting out with nonisolated. But then all out generated L10n structs would need to be MainActor as well which will cause some troubles, since main actor isolation is not available everywhere where L10n is used. Probably fine to keep it unsafe for now.

laevandus · 2025-05-09T10:18:37Z

DemoAppSwiftUI/ChannelHeader/ChooseChannelQueryView.swift

-    static let queryIdentifiers = ChannelListQueryIdentifier.allCases.sorted(using: KeyPathComparator(\.title))
+    static var queryIdentifiers: [ChannelListQueryIdentifier] {
+        ChannelListQueryIdentifier.allCases.sorted(by: { $0.title < $1.title })
+    }


It was giving Sendable related error which did not feel right. Just switched to another sorting method.

laevandus · 2025-05-09T10:19:46Z

DemoAppSwiftUI/LoginViewModel.swift

@@ -42,7 +42,7 @@ class LoginViewModel: ObservableObject {
                return
            }

-            DispatchQueue.main.async { [weak self] in
+            Task { @MainActor [weak self] in


DispatchQueue gives Sendable error for self

laevandus · 2025-05-09T10:22:30Z

Sources/StreamChatSwiftUI/ChatChannel/ChannelInfo/AddUsersViewModel.swift

@@ -6,7 +6,7 @@ import StreamChat
 import SwiftUI

 /// View model for the `AddUsersView`.
-class AddUsersViewModel: ObservableObject {
+@MainActor class AddUsersViewModel: ObservableObject {


Since view model factory is MainActor and view models are used from view, then it made more than sense to make all the view models main actor.

laevandus · 2025-05-09T10:23:52Z

Sources/StreamChatSwiftUI/ChatChannel/ChannelInfo/AddUsersViewModel.swift

-                guard let self = self else { return }
-                self.users = self.searchController.userArray
-                self.loadingNextUsers = false
+                MainActor.ensureIsolated { [weak self] in


Controllers do not ensure on the compilation level which actor is used. We can use any queue for controller completion handlers although the default is main. Therefore, we need to make sure that main is used. Applies to all the completion handlers and controller delegates.

laevandus · 2025-05-09T10:24:57Z

Sources/StreamChatSwiftUI/ChatChannel/ChannelInfo/ChatChannelInfoViewModel.swift

@@ -172,7 +172,7 @@ public class ChatChannelInfoViewModel: ObservableObject, ChatChannelControllerDe
        loadAdditionalUsers()
    }

-    public func leaveConversationTapped(completion: @escaping () -> Void) {
+    public func leaveConversationTapped(completion: @escaping @MainActor() -> Void) {


For avoiding actor isolation in the view. Better force main on the view model level.

laevandus · 2025-05-09T10:27:50Z

...ces/StreamChatSwiftUI/ChatChannel/Composer/Suggestions/Mentions/MentionsCommandHandler.swift

@@ -152,15 +152,16 @@ public struct MentionsCommandHandler: CommandHandler {

    private func searchAllUsers(for typingMention: String) -> Future<SuggestionInfo, Error> {
        Future { promise in
+            nonisolated(unsafe) let unsafePromise = promise


Promise is not sendable even when making SuggestionInfo sendable, added a unsafe check here for bypassing it.

laevandus · 2025-05-09T10:35:19Z

Sources/StreamChatSwiftUI/ChatChannel/Composer/PhotoAssetsUtils.swift

@@ -80,8 +80,9 @@ public class PhotoAssetLoader: NSObject, ObservableObject {

        exportSession.outputURL = outputURL
        exportSession.outputFileType = .mp4
+        nonisolated(unsafe) let unsafeSession = exportSession


There is a Swift 6 friendly export function, but we can't use it because it does not support iOS 13. Suppressing the concurrency error here.

laevandus · 2025-05-09T10:36:37Z

Sources/StreamChatSwiftUI/ChatChannel/MessageList/GiphyAttachmentView.swift

@@ -103,7 +103,7 @@ struct LazyGiphyView: View {
    var body: some View {
        LazyImage(imageURL: source) { state in
            if let imageContainer = state.imageContainer {
-                NukeImage(imageContainer)
+                Image(uiImage: imageContainer.image)


Nuke was upgraded to 12.8 and LazyImage has some breaking changes.

laevandus · 2025-05-09T10:38:00Z

Sources/StreamChatSwiftUI/ChatChannel/MessageList/LinkAttachmentView.swift

+                    LazyImage(imageURL: linkAttachment.previewURL ?? linkAttachment.originalURL) { state in
+                        if let image = state.image {
+                            image
+                                .resizable()
+                                .aspectRatio(contentMode: .fill)
+                        }
+                    }


LazyImage has breaking changes and requires to be used like above for getting the resize to fill behavior

laevandus · 2025-05-09T10:40:03Z

Sources/StreamChatSwiftUI/ChatChannel/MessageList/ReactionsIconProvider.swift

+        let color = containsUserReaction ?
+            InjectedValues[\.colors].reactionCurrentUserColor :
+            InjectedValues[\.colors].reactionOtherUserColor


Color is struct and reactionCurrentUserColor is lazy var which triggers mutation. Swift 6 was not happy if colors was static var since then static var needs to be made concurrency safe. Ignored the error by switching to accessing injected values directly.

laevandus · 2025-05-09T10:42:02Z

Sources/StreamChatSwiftUI/ChatChannel/Reactions/MessageActions/DefaultMessageActions.swift

+        onFinish: @escaping @MainActor(MessageActionInfo) -> Void,
+        onError: @escaping @MainActor(Error) -> Void


It is a though one since these functions are used in views, which means that it makes sense to force MainActor. Downside is that it changes public API and ends up changing some view factory methods related to actions (SDK user will get a warning after upgrading the SDK).

laevandus · 2025-05-09T10:44:15Z

Sources/StreamChatSwiftUI/ChatChannel/Reactions/ReactionsOverlayContainer.swift

@@ -60,7 +60,7 @@ struct ReactionsOverlayContainer: View {

 public extension ChatMessage {

-    func reactionOffsetX(
+    @preconcurrency @MainActor func reactionOffsetX(


Uses UIScreen.main which requires MainActor

laevandus · 2025-05-09T10:45:36Z

Sources/StreamChatSwiftUI/ChatChannel/ChatChannelDataSource.swift

@@ -5,7 +5,7 @@
 import StreamChat

 /// Data source providing the chat messages.
-protocol MessagesDataSource: AnyObject {
+@MainActor protocol MessagesDataSource: AnyObject {


Since it is used by main actor view model, then makes sense to force it to main actor from the beginning. Note that then delegate implementation does not require nonisolated which makes it cleaner.

Sources/StreamChatSwiftUI/ChatChannel/ChatChannelDataSource.swift

laevandus · 2025-05-09T10:47:13Z

Sources/StreamChatSwiftUI/ChatChannel/ChatChannelViewModel.swift

-            ImageCache.shared.trim(toCost: utils.messageListConfig.cacheSizeOnChatDismiss)
-            if !channelDataSource.hasLoadedAllNextMessages {
-                channelDataSource.loadFirstPage { _ in }
+        MainActor.ensureIsolated {


Isolated deinits are coming, but not available yet

laevandus · 2025-05-09T10:48:10Z

Sources/StreamChatSwiftUI/ChatChannelList/ChannelAvatarsMerger.swift

+    private var images: Images { InjectedValues[\.images] }
+    private var utils: Utils { InjectedValues[\.utils] }

    /// Context provided utils.
-    private lazy var imageProcessor = utils.imageProcessor
-    private lazy var imageMerger = utils.imageMerger
+    private var imageProcessor: ImageProcessor { utils.imageProcessor }
+    private var imageMerger: ImageMerging { utils.imageMerger }

    /// Placeholder images.
-    private lazy var placeholder1 = images.userAvatarPlaceholder1
-    private lazy var placeholder2 = images.userAvatarPlaceholder2
-    private lazy var placeholder3 = images.userAvatarPlaceholder3
-    private lazy var placeholder4 = images.userAvatarPlaceholder4
+    private var placeholder1: UIImage { images.userAvatarPlaceholder1 }
+    private var placeholder2: UIImage { images.userAvatarPlaceholder2 }
+    private var placeholder3: UIImage { images.userAvatarPlaceholder3 }
+    private var placeholder4: UIImage { images.userAvatarPlaceholder4 }


Making everything getter here avoids making lazy var properties concurrency safe. Note that these are indeed called from different threads.

laevandus · 2025-05-09T10:49:10Z

Sources/StreamChatSwiftUI/ChatChannelList/ChannelHeaderLoader.swift

@@ -36,7 +36,7 @@ open class ChannelHeaderLoader: ObservableObject {
    private var loadedImages = [ChannelId: UIImage]()
    private let didLoadImage = PassthroughSubject<ChannelId, Never>()

-    public init() {
+    nonisolated public init() {


Otherwise Utils can't init it in-place and adding any MainActor isolation to Utils is not feasible.

laevandus · 2025-05-09T10:51:21Z

Sources/StreamChatSwiftUI/ChatChannelList/ChatChannelHelperViews.swift

@@ -127,9 +127,9 @@ struct TabBarAccessor: UIViewControllerRepresentable {
 }

 var isIphone: Bool {
-    UIDevice.current.userInterfaceIdiom == .phone
+    UITraitCollection.current.userInterfaceIdiom == .phone


UIDevice is main actor whereas UITraitCollection is not

laevandus · 2025-05-09T10:55:09Z

Sources/StreamChatSwiftUI/StreamNuke/Nuke/Caching/DataCache.swift

-    /// Sweeps are performed in a background and can be performed in parallel
-    /// with reading.
-    var sweepInterval: TimeInterval = 30
+    /// The time interval between cache sweeps. The default value is 1 hour.


Everything under StreamNuke does not need reviewing since it was Nuke's version upgrade without any manual changes.

laevandus · 2025-05-09T10:59:01Z

Sources/StreamChatSwiftUI/Utils/Errors.swift

@@ -14,7 +14,7 @@ public struct StreamChatError: Error {
    public let description: String?

    /// The additional information dictionary.
-    public let additionalInfo: [String: Any]?
+    public nonisolated(unsafe) let additionalInfo: [String: Any]?


It has Any, which can't be Sendable (note that Error is Sendable). Skipping the sendable check here (breaking change to change Any here)

laevandus · 2025-05-09T11:04:36Z

Sources/StreamChatSwiftUI/DefaultViewFactory.swift

+        onDismiss: @escaping @MainActor() -> Void,
+        onError: @escaping @MainActor(Error) -> Void


This will give a build warning for SDK users who override it in their view factory. Needs to be highlighted in the CHANGELOG

laevandus · 2025-05-09T11:05:57Z

Sources/StreamChatSwiftUI/Utils.swift

+    @preconcurrency @MainActor
    public lazy var audioSessionFeedbackGenerator: AudioSessionFeedbackGenerator = StreamAudioSessionFeedbackGenerator()


Apple's feedback generator's init is MainActor, therefore it is really difficult to not have our wrapper nonisolated.

StreamChatSwiftUITests/Infrastructure/Mocks/MockBackgroundTaskScheduler.swift

laevandus · 2025-05-09T11:08:36Z

StreamChatSwiftUITests/Infrastructure/TestTools/ChatClient_Mock.swift

@@ -22,7 +22,15 @@ public extension ChatClient {
            config: config,
            workerBuilders: [],
            environment: .init(
-                apiClientBuilder: APIClient_Spy.init,
+                apiClientBuilder: {
+                    APIClient_Spy(


Sendable warning if not written out with all the arguments

laevandus · 2025-05-09T11:10:53Z

StreamChatSwiftUITests/Tests/StreamChatTestCase.swift

@@ -21,7 +21,7 @@ open class StreamChatTestCase: XCTestCase {

    public var streamChat: StreamChat?

-    override open func setUp() {
+    @MainActor override open func setUp() {


Many tests want to change main actor isolated types, therefore it is easier to require main actor in a single place

laevandus · 2025-05-09T11:11:21Z

StreamChatSwiftUITestsAppTests/Pages/MessageListPage.swift

@@ -371,7 +371,7 @@ class MessageListPage {

    enum ComposerMentions {
        static var cells: XCUIElementQuery {
-            app.scrollViews["CommandsContainerView"].otherElements.matching(NSPredicate(format: "identifier LIKE 'MessageAvatarView'"))
+            app.scrollViews["CommandsContainerView"].images.matching(NSPredicate(format: "identifier LIKE 'MessageAvatarView'"))


Nuke's LazyImage changes causes it

sonarqubecloud · 2025-05-09T13:40:25Z

Quality Gate failed

Failed conditions
39.4% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

laevandus added 10 commits March 28, 2025 11:40

Use SWIFT_STRICT_CONCURRENCY complete with Swift 5

ddf78cc

Merge branch 'develop' into swift-6

b73c9c5

# Conflicts: # StreamChatSwiftUI.xcodeproj/project.pbxproj

Make view models MainActor and fix isolation for controller delegates…

2f64d75

… and completions

Set Swift version to 6

87292cf

Constraint and UIDevice errors

ab7356d

Try MainActor Appearance and non-isolated injected values

391b156

Upgrade Nuke to 12.8

26dd6aa

Fixed all the errors

ef3bbc0

Fix last warnings

bb0ed90

Fix Swift 6 warnings in tests

87fcb5a

laevandus requested a review from a team as a code owner May 7, 2025 12:08

laevandus marked this pull request as draft May 7, 2025 12:08

Disable building with Xcode 15

994196f

Fix tests

4c94da4

laevandus commented May 7, 2025

View reviewed changes

laevandus commented May 8, 2025

View reviewed changes

laevandus added 5 commits May 8, 2025 10:29

Fix tests

6b78288

Merge branch 'develop' into swift-6

8eae0dd

Fix build warnings in the demo app

6e1e8c9

Fix avatar sizes with LazyImage

f10725c

Fix UI test where LazyImage now is treated as images, not otherElements

c0b9111

laevandus commented May 9, 2025

View reviewed changes

Sources/StreamChatSwiftUI/ChatChannel/ChatChannelDataSource.swift Show resolved Hide resolved

laevandus commented May 9, 2025

View reviewed changes

StreamChatSwiftUITests/Infrastructure/Mocks/MockBackgroundTaskScheduler.swift Outdated Show resolved Hide resolved

laevandus commented May 9, 2025

View reviewed changes

laevandus added 3 commits May 9, 2025 14:25

Tidy here and there

79ef1c1

Use Swift 6 in the demo app

e28503d

Merge branch 'develop' into swift-6

f8d9504

laevandus added 🤞 Ready for QA ⏫ Dependencies Update Pull requests that update a dependency file 🪧 Demo App An Issue or PR related to the Demo App ✅ Feature An issue or PR related to a feature labels May 9, 2025

laevandus added 2 commits May 9, 2025 15:12

Fix runtime asserts

fa2872a

Fix Gif support which LazyImage dropped

4b305c5

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Swift 6: complete concurrency checking #825

Swift 6: complete concurrency checking #825

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sonarqubecloud bot commented May 9, 2025

		static var `default`: Appearance = .init()
		nonisolated(unsafe) static var `default`: Appearance = .init()

		onFinish: @escaping @MainActor(MessageActionInfo) -> Void,
		onError: @escaping @MainActor(Error) -> Void

		onDismiss: @escaping @MainActor() -> Void,
		onError: @escaping @MainActor(Error) -> Void

		@preconcurrency @MainActor
		public lazy var audioSessionFeedbackGenerator: AudioSessionFeedbackGenerator = StreamAudioSessionFeedbackGenerator()

Swift 6: complete concurrency checking #825

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Swift 6: complete concurrency checking #825

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laevandus commented May 7, 2025 • edited Loading

🔗 Issue Links

🎯 Goal

📝 Summary

🛠 Implementation

🎨 Showcase

🧪 Manual Testing Notes

☑️ Contributor Checklist

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sonarqubecloud bot commented May 9, 2025

Quality Gate failed

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