stream-chat-swift Swift 6: complete concurrency checking for StreamChatUI

[!IMPORTANT] Merges to the main swift-6 branch, not develop

🔗 Issue Links

🎯 Goal

Set Swift version to 6 and implement complete concurrency checking in StreamChatUI

📝 Summary

Completion blocks need to be @Sendable in most of the cases
Controller completions and delegates must ensure main thread (through custom StreamConcurrency.onMain)
Controller delegates get nonisolated because any thread thread could call it and often MainActor guarded type implements these delegates (e.g. UIViewController subclass)
Tests use nonisolated(unsafe) a lot because otherwise most of the test must be rewritten (huge effort)
Sendable conformance to many types
Many protocols and types related to UI get @MainActor requirement
Upgrade Nuke to version 12.8 (otherwise we can't compile with complete concurrency checking)
Patch SwiftyGif for supporting complete concurrency checking

🛠 Implementation

LLC controllers support any queue for delegate callbacks and completion handlers. Therefore we need to ensure that these run on the main thread when updating UI code. This is where the custom MainActor.ensureIsolated(_) comes into the play. It just ensures that code triggered from these code paths are always on the main thread.

Public API which requires MainActor are annotated with @preconcurrency @MainActor which is the backwards compatibility support. In the next major version we would clean it up.

🧪 Manual Testing Notes

Manual testing in #3661

☑️ Contributor Checklist

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

May 05 '25 07:05 laevandus

1 Warning

:warning: Big PR

1 Message

:book: 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.

	1 Warning
:warning:	Big PR

	1 Message
:book:	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 :no_entry_sign: Danger

May 05 '25 07:05 github-actions[bot]

SDK Size

`title`	`develop`	`branch`	`diff`	`status`
StreamChat	7.2 MB	7.28 MB	+81 KB	🟢
StreamChatUI	4.72 MB	4.77 MB	+55 KB	🟢

May 05 '25 07:05 Stream-SDK-Bot

SDK Performance

`target`	`metric`	`benchmark`	`branch`	`performance`	`status`
MessageList	Hitches total duration	10 ms	10.01 ms	-0.1% 🔽	🟡
	Duration	2.6 s	2.54 s	2.31% 🔼	🟢
	Hitch time ratio	4 ms per s	3.94 ms per s	1.5% 🔼	🟢
	Frame rate	75 fps	78.37 fps	4.49% 🔼	🟢
	Number of hitches	1	1.2	-20.0% 🔽	🔴

May 05 '25 07:05 Stream-SDK-Bot

SDK Size

`title`	`develop`	`branch`	`diff`	`status`
StreamChat	7.2 MB	7.28 MB	+81 KB	🟢
StreamChatUI	4.72 MB	4.8 MB	+87 KB	🟢

May 05 '25 11:05 Stream-SDK-Bot

SDK Performance

`target`	`metric`	`benchmark`	`branch`	`performance`	`status`
MessageList	Hitches total duration	10 ms	5.01 ms	49.9% 🔼	🟢
	Duration	2.6 s	2.55 s	1.92% 🔼	🟢
	Hitch time ratio	4 ms per s	1.97 ms per s	50.75% 🔼	🟢
	Frame rate	75 fps	77.93 fps	3.91% 🔼	🟢
	Number of hitches	1	0.6	40.0% 🔼	🟢

May 23 '25 11:05 Stream-SDK-Bot

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