Pass exceptions to JS that are thrown by JS functions in an async context

[ekraihan]

Is your feature request related to a problem? Please describe.

When invoking an async function, the only way to notify JS of exceptions thrown by the function is by checking the result of every async JS function call and invoking napi_fatal_exception if needed. It would be great if napi_fatal_exception was called automatically when exceptions propagate out of an async function.

Describe the solution you'd like

I would like the invoker of napi_threadsafe_function_call_js (which is passed into napi_create_threadsafe_function) to detect when exceptions bubble out of the async callback and call napi_fatal_exception(env, error); Currently, the napi_threadsafe_function_call_js is invoked by node_napi_env::CallIntoModule which runs the code

call(this); // invokes the napi_threadsafe_function_call_js
// ...
if (!last_exception.IsEmpty()) {
    handle_exception(this, last_exception.Get(this->isolate));
    last_exception.Reset();
}

where handle_exception by default calls v8::Isolate::ThrowException which does nothing in an async context.

Describe alternatives you've considered

Perhaps the real problem here is that v8::Isolate::ThrowException does not propagate exceptions to JS when invoked in an async context? Perhaps this is a bug with v8?

[targos]

/cc @nodejs/n-api

[mhdawson]

@legendecas just submitted a PR to uncaught exceptions so he will take a look at this one and comment.

[legendecas]

I think this is what #36510 intended to fix.