Is it possible to hook into an asynchronous function?

[nabetti1720]

Hello everyone, I'm part of an experimental project called LLRT. As you know, LLRT uses quickjs-ng through RquickJS (Rust binding). I'm very grateful to be able to use such a great js engine.

Currently, we are trying to implement async_hooks, which is one of the nodejs modules. A draft has been made, but we want to make it better.

The current implementation creates hooking points for Promise, setTimeout, and setImmediate by patching JavaScript, but we would prefer something more native.

Current Implementation :
https://github.com/awslabs/llrt/pull/947/files#diff-801982e5802bc4502f37e9606801a09f83274a59675f658ee91eac80c54925a5

Is there a better way?

[bnoordhuis]

async_hooks in node is implemented using V8's PromiseHook(s)¹ API. Assuming you're familiar with it, would that work for you?

¹ V8 is not wholly consistent on whether it's singular or plural...

[nabetti1720]

I'm not that familiar with asynchronous processing, but I'm hoping that the js engine has something like this, as you say.

Promise lifecycle hooks in V8 (It's a bit of an old document) :
https://docs.google.com/document/d/1rda3yKGHimKIhg5YeoAmCOtyURgsbTH_qaYR79FELlk/edit?tab=t.0#heading=h.sdpzjcyw06a5

[saghul]

Adding an API inspired by V8's sounds like a good idea to me!

[bnoordhuis]

@nabetti1720 can you check if #1033 works for you?