Easier debuggability for pending promises after a test has finished

[jespertheend]

Sometimes in tests I run across the following message:

Promise resolution is still pending but the event loop has already resolved.

but I just can't pin down where the pending promise is being created.
Just now I simply forgot to call FakeTime.prototype.restore(), but it took me a good couple of minutes to figure out what was happening.

I feel like Deno has some information here that could be communicated to the user to make debugging these cases easier. Like showing a stack trace to the pending promises.

Not sure if V8 exposes that sort of thing though, maybe what I'm asking here is impossible.

[bartlomieju]

This should be easy to fix - the error is returned in JsRuntime::poll_value - we should add a call to find_stalled_top_level_await() there that will give a stack trace for the promise that is unresolved. @jespertheend would you be interested in implementing that?

[jespertheend]

I mean, I can try 😅

[bartlomieju]

Just open a PR and we can work from there :)

[jespertheend]

Alright, I'll have some free time in a couple of hours.

[jespertheend]

I've submitted #17813 but am running into a panic, that I'm not really sure how to resolve: #17813 (comment)