Main thread isolation in VideoView

[pblazej]

This is a tiny change, but prevents a crash in .v6 mode by fixing an important inconsistency.

• OnDidMutate is called within the critical section - so from any thread
• for Sendable classes, it doesn't make much difference though
• for @MainActor methods like mainSyncOrAsync it does, as they:
  • were still @MainActor isolated
  • were called from bg threads - which is checked at runtime now

So the idea is mainSyncOrAsync signature now reflects what really happens here:

• it must be nonisolated itself as it's called from a @Sendable OnDidMutate 💚
• the body is compile-time @MainActor 💚
• the "switch" happens inside the method, not "accidentally outside"

The crash will happen during video track publication, the stack trace is pretty clear:

[ilo-nanpa]

it seems like you haven't added any nanpa changeset files to this PR.

if this pull request includes changes to code, make sure to add a changeset, by writing a file to .nanpa/<unique-name>.kdl:

minor type="added" "Introduce frobnication algorithm"

refer to the manpage for more information.

[pblazej]

This MainActor is necessary only for <5.9 due to lack of assumeIsolate as you see below 🫳

[hiroshihorie]

I couldn't repo the crash with main, how can I repo the crash ?

[pblazej]

I couldn't repo the crash with main, how can I repo the crash ?

I used Xcode 16.2 with Package 6.0 - every video track publish will fail 💣

[pblazej]

@hiroshihorie still unable to pull that one spec.dependency("LiveKitWebRTC", "= 125.6422.28")

[hiroshihorie]

@hiroshihorie still unable to pull that one spec.dependency("LiveKitWebRTC", "= 125.6422.28")

I haven't pushed that pod lib yet