Are some promise functions guaranteed to complete synchronously?

[PJB3005]

The specification for functions like requestAdapter() says they return a promise. On the Rust side this is returned as a Future, and on the C header side this is exposed as a callback. All well and good.

However, the example in the repo assumes the call will complete synchronously and have written the result by the time the function returns. I have also seen other tutorials assert that "in practice it will be synchronous".

Is this a guarantee for the future? Or is it simply a shortcut taken by the C example to keep it simple for now?

(Also, is this where these questions go? I couldn't even find where webgpu-headers comes from spec wise, the W3C spec makes no mention of the native header format)

[almarklein]

Good question! As I have understood it, the callback will eventually run asynchronous, but the event-loop mechanism has not been fleshed out yet.

In wgpu-py we also assume it runs synchronous for the time being:
https://github.com/pygfx/wgpu-py/blob/402961a04299a1518ac0fb7ad3dbb44636679dbb/wgpu/backends/rs.py#L280-L282

[PJB3005]

If the event loop will have to be pumped from the app side, then I guess I don't want to try doing anything in advance for it. I'll just keep assuming they're synchronous for now too then.