Migrate `DocumentManager.queue` from `DispatchQueue` to `AsyncQueue`

[ahoppen]

AsyncQueue works better with the rest of the Swift concurrency system (eg. priority escalation) and we should use AsyncQueue instead of DispatchQueue for DocumentManager.queue.

[ahoppen]

Synced to Apple’s issue tracker as rdar://132934990

[AbdAlRahmanGad]

Hi @ahoppen,

can you assign me this issue?

[ahoppen]

Thanks for looking at this @AbdAlRahmanGad 🙏🏽

[DPrakashh]

Hi @ahoppen , I noticed this issue hasn't had an update in a while. I've just finished the updates on my Snippet PR (#2387) and would love to help migrate DocumentManager to AsyncQueue if this is still available! ? I am asking this as this is already assigned to someone else .

[ahoppen]

I think I briefly looked at this myself and decided that AsyncQueue isn’t actually the right approach for this because almost all methods on DocumentManager would need to become synchronous. We should still migrate away from DispatchQueue IMO and a ThreadSafeBox for documents is probably the right approach here. If you’d like to look into making that change, that would be great.

[DPrakashh]

Thanks for the feedback, Alex! That makes perfect sense—avoiding a massive async refactor of DocumentManager is definitely a better approach. I’d be happy to migrate the documents dictionary to use a ThreadSafeBox instead.

I am finishing the final polish on the Code Completion PR (#2387) right now to ensure that is 100% ready. I will dive into this refactoring task immediately after that is submitted!