Swift 6: complete concurrency checking (LLC and UIKit) #3661

laevandus · 2025-05-05T12:26:55Z

Important

StreamChatUI changes are in #3660 and will be merged to here. This PR can be reviewed already.

🔗 Issue Links

Resolves IOS-735

🎯 Goal

Set Swift version to 6 and implement complete concurrency checking

📝 Summary

Sendable conformance to types
@Sendable to completion handlers
Many thread-safety related changes to @unchecked Sendable types (internal classes have manual handling and found many which did not guard that state properly)
Fixes warnings in the demo app (adding @Sendable to completion handlers creates warnings at callsites)
Backported AllocatedUnfairLock which is needed for static concurrency safe properties (our Atomic property wrapper can't be used)

🛠 Implementation

🧪 Manual Testing Notes

Manual regression testing round when UIKit changes are merged into this branch.

☑️ 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: # Sources/StreamChat/WebSocketClient/BackgroundTaskScheduler.swift

# Conflicts: # Sources/StreamChat/Models/CurrentUser.swift # Sources/StreamChat/Workers/CurrentUserUpdater.swift

github-actions · 2025-05-05T12:27:57Z

	1 Message
📖	Skipping Danger since the Pull Request is classed as `Draft`/`Work In Progress`

Generated by 🚫 Danger

laevandus · 2025-05-05T12:29:31Z

.github/workflows/smoke-checks.yml

-    if: ${{ github.event.inputs.record_snapshots != 'true' }}
+    # if: ${{ github.event.inputs.record_snapshots != 'true' }}
+    if: false # disable Xcode 15 builds


Disabled Xcode 15 builds (it is hard to support it when complete concurrency checking is enabled). Hard means avoiding compiler crashes.

Stream-SDK-Bot · 2025-05-05T12:31:39Z

SDK Size

`title`	`develop`	`branch`	`diff`	`status`
StreamChat	7.2 MB	7.28 MB	+81 KB	🟢
StreamChatUI	4.72 MB	4.73 MB	+17 KB	🟢

laevandus · 2025-05-05T12:33:12Z

Sources/StreamChat/Audio/Analysis/AudioAnalysing.swift

@@ -26,7 +26,7 @@ final class StreamAudioWaveformAnalyser: AudioAnalysing {
    private let audioSamplesExtractor: AudioSamplesExtractor
    private let audioSamplesProcessor: AudioSamplesProcessor
    private let audioSamplesPercentageNormaliser: AudioValuePercentageNormaliser
-    private let outputSettings: [String: Any]
+    nonisolated(unsafe) private let outputSettings: [String: Any]


nonisolated(unsafe) because value is Any

Stream-SDK-Bot · 2025-05-05T12:35:58Z

SDK Performance

`target`	`metric`	`benchmark`	`branch`	`performance`	`status`
MessageList	Hitches total duration	10 ms	1.67 ms	83.3% 🔼	🟢
	Duration	2.6 s	2.53 s	2.69% 🔼	🟢
	Hitch time ratio	4 ms per s	0.66 ms per s	83.5% 🔼	🟢
	Frame rate	75 fps	78.53 fps	4.71% 🔼	🟢
	Number of hitches	1	0.2	80.0% 🔼	🟢

laevandus · 2025-05-05T12:38:00Z

Sources/StreamChat/Utils/BoxedAny.swift

+
+import Foundation
+
+/// Erase type for structs which recursively contain themselves.


It is easier to use a type instead of a closure when dealing with Sendable.

yes, this is a nice approach

laevandus · 2025-05-05T12:51:10Z

Sources/StreamChat/Audio/AudioPlayer/AudioPlaying.swift

@@ -131,15 +131,19 @@ open class StreamAudioPlayer: AudioPlaying, AppStateObserverDelegate {
    open func play() {
        do {
            try audioSessionConfigurator.activatePlaybackSession()
-            player.play()
+            MainActor.ensureIsolated {
+                player.play()


Note that AVPlayer and some asset related methods require main actor

laevandus · 2025-05-05T12:53:02Z

Sources/StreamChat/Config/StreamRuntimeCheck.swift

+
+    // MARK: -
+
+    private static let queue = DispatchQueue(label: "io.getstream.stream-runtime-check", target: .global())


Alternative is to skip using queue here and making everything nonisolated(unsafe), especially because these are internal runtime checkes.

I would do that without a queue here actually

sonarqubecloud · 2025-05-19T07:12:31Z

Quality Gate passed

Issues
68 New issues
0 Accepted issues

Measures
0 Security Hotspots
86.7% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

martinmitrevski

Looks good in general, left some comments to discuss

martinmitrevski · 2025-05-18T21:18:24Z

Sources/StreamChat/Config/StreamRuntimeCheck.swift

+
+    // MARK: -
+
+    private static let queue = DispatchQueue(label: "io.getstream.stream-runtime-check", target: .global())


I would do that without a queue here actually

martinmitrevski · 2025-05-19T07:32:38Z

Sources/StreamChat/APIClient/CDNClient/CDNClient.swift

    static var maxAttachmentSize: Int64 { 100 * 1024 * 1024 }

    private let decoder: RequestDecoder
    private let encoder: RequestEncoder
    private let session: URLSession
    /// Keeps track of uploading tasks progress
-    @Atomic private var taskProgressObservers: [Int: NSKeyValueObservation] = [:]


did it complain about Atomic?

martinmitrevski · 2025-05-19T07:35:52Z

Sources/StreamChat/Audio/AudioPlayer/AudioPlaying.swift

@@ -131,15 +131,19 @@ open class StreamAudioPlayer: AudioPlaying, AppStateObserverDelegate {
    open func play() {
        do {
            try audioSessionConfigurator.activatePlaybackSession()
-            player.play()
+            MainActor.ensureIsolated {


mentioned it on the other PR as well - why do we need to use ensureIsolated?

martinmitrevski · 2025-05-19T07:39:33Z

Sources/StreamChat/Controllers/EventsController/EventsController.swift

@@ -50,6 +50,8 @@ public class EventsController: Controller, DelegateCallable {
        get { multicastDelegate.mainDelegate }
        set { multicastDelegate.set(mainDelegate: newValue) }
    }
+
+    private let queue = DispatchQueue(label: "io.getstream.events-controller", target: .global())


where is this used?

martinmitrevski · 2025-05-19T07:44:14Z

Sources/StreamChat/Database/DatabaseContainer.swift

+        }
+    }
+
+    func writeConverting<T>(_ actions: @escaping @Sendable(DatabaseSession) throws -> T) async throws -> T where T: Sendable {


why do we need this?

martinmitrevski · 2025-05-19T08:17:46Z

Sources/StreamChat/Utils/AllocatedUnfairLock.swift

+import os
+
+@available(iOS, introduced: 13.0, deprecated: 16.0, message: "Use OSAllocatedUnfairLock instead")
+final class AllocatedUnfairLock<State>: @unchecked Sendable {


where do we use an unfair lock?

martinmitrevski · 2025-05-19T08:19:20Z

Sources/StreamChat/Utils/BoxedAny.swift

+
+import Foundation
+
+/// Erase type for structs which recursively contain themselves.


yes, this is a nice approach

martinmitrevski · 2025-05-19T08:29:27Z

Sources/StreamChat/Utils/MainQueue+Synchronous.swift

-            try action()
-        } else {
-            try DispatchQueue.main.sync {
+            return try MainActor.assumeIsolated {


why is this needed?

martinmitrevski · 2025-05-19T08:32:04Z

Sources/StreamChat/Utils/StreamCollection.swift

-        _endIndex = { baseCollection.endIndex }
-        _position = { baseCollection[$0] }
-        _startIndex = { baseCollection.startIndex }
+        self.baseCollection = Array(baseCollection)


why do we change this?

martinmitrevski · 2025-05-19T08:37:45Z

Sources/StreamChat/WebSocketClient/WebSocketPingController.swift

-        pongTimeoutTimer = timerType.schedule(timeInterval: Self.pongTimeoutTimeInterval, queue: timerQueue) { [weak self] in
-            log.info("WebSocket Pong timeout. Reconnect")
-            self?.delegate?.disconnectOnNoPongReceived()
+        queue.sync {


why is this needed?

laevandus added 14 commits March 24, 2025 12:43

Swift 6 for LLC

021ae9a

Fix share sheet compilation

16e5611

Fallback to Swift 5 if Xcode 15 is used

70d77ab

Xcode 15 compatibility

764072a

Use SWIFT_STRICT_CONCURRENCY complete with Swift 5

fcbd4ea

Fix Sendable and MainActor warnings in the demo app

0d34d9c

Reset ScheduledStreamTimer

823861b

Merge branch 'develop' into swift-6

e04c599

# Conflicts: # Sources/StreamChat/WebSocketClient/BackgroundTaskScheduler.swift

Add documentation

e2bd195

Merge branch 'develop' into swift-6

2a776a9

# Conflicts: # Sources/StreamChat/Models/CurrentUser.swift # Sources/StreamChat/Workers/CurrentUserUpdater.swift

Fix tests after merging develop

c55efc7

Add missing Sendable annotations to new additions

c76c13d

Disable Xcode 15 builds

143a30f

Disable Xcode 15 builds

7b05ced

laevandus requested a review from a team as a code owner May 5, 2025 12:26

laevandus added the 🌐 SDK: StreamChat (LLC) Tasks related to the StreamChat LLC SDK label May 5, 2025

laevandus marked this pull request as draft May 5, 2025 12:27

laevandus commented May 5, 2025

View reviewed changes

laevandus changed the title ~~Swift 6: complete concurrency checking~~ Swift 6: complete concurrency checking (LLC and UIKit) May 5, 2025

laevandus mentioned this pull request May 5, 2025

Swift 6: complete concurrency checking for StreamChatUI #3660

Draft

6 tasks

laevandus added 3 commits May 6, 2025 12:38

Set Swift version to 6

2c24b9e

MainActor errors in MockAVPlayer

d4c1277

Fix Swift 6 errors in test tools (use unfair lock for static properties)

46d55a6

laevandus added 4 commits May 7, 2025 15:28

Update demo app to use Task instead of ensureIsolated

326a384

Use Swift 5 for mock server

592e529

Merge branch 'develop' into swift-6

5631542

Merge branch 'develop' into swift-6

bcdf40b

martinmitrevski reviewed May 19, 2025

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Swift 6: complete concurrency checking (LLC and UIKit) #3661

Swift 6: complete concurrency checking (LLC and UIKit) #3661

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		import Foundation

		/// Erase type for structs which recursively contain themselves.


		// MARK: -

		private static let queue = DispatchQueue(label: "io.getstream.stream-runtime-check", target: .global())

Swift 6: complete concurrency checking (LLC and UIKit) #3661

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Swift 6: complete concurrency checking (LLC and UIKit) #3661

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laevandus commented May 5, 2025 • edited Loading

🔗 Issue Links

🎯 Goal

📝 Summary

🛠 Implementation

🧪 Manual Testing Notes

☑️ Contributor Checklist

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SDK Size

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sonarqubecloud bot commented May 19, 2025

Quality Gate passed

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laevandus commented May 5, 2025 •

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