Allow using boa in an async context

[CodeDoctorDE]

Hello,

I'm currently trying to add boa to flutter. Based on the feedback of the bridge author (fzyzcjy/flutter_rust_bridge#2257) Context needs to be sendable (implement Send).
Can you add it? Do you have a better idea how I could integrate it? I'm currently using a Arc<Mutex<Context>> for this.

[jedel1043]

Converted to discussion because this is more of a question thing.

[jedel1043]

In general, a Context cannot be Send because the ECMAScript spec is pretty clear that execution contexts are single-threaded. This fact is used by Boa with some thread local data for certain things like garbage collecting, which automatically makes Context not Send since it keeps track of objects that can only be accessed by the thread local GC.

I think the most common workaround for this is to have a thread local Context, which should allow accessing it globally, with the caveat that any new thread would create its own Context and Realm to execute things on.

[thautwarm]

As I'm one who also uses both flutter_rust_bridge and boajs, I believe this might not satisfy the use case.
Boa is for scripting, and I don't really need multi-thread processing here.
Hence, a workaround might be creating a worker thread to run boajs, and async stuffs can communicate with the worker thread using messages that are Send.

[jedel1043]

Yeah, if you don't need multithreading and if you don't run scripts often enough to cause contention between threads, a dedicated thread for the engine would also work