AsyncResource.bind does not forward arguments

[lroal]

Using Node 12.19.0:
When binding a function with AsyncResource.bind, the arguments are not forwarded.
I had to write this workaround to make it work:

function bindWorkAround(cb) {
	AsyncResource.bind(invokeOriginal);
	let _arguments;
	return onData;

	function onData() {
		_arguments = arguments;
		invokeOriginal();
	}

	function invokeOriginal() {
		cb.apply(null, _arguments);
	}

}

[mmomtchev]

@lroal, can you please edit your issue to include the code that does not work and describe what you expect to happen? You can also include the workaround, but what is the most important is the code that does not work.

[lroal]

Here is the example, @mmomtchev .
I expect it to print 'foo' instead of undefined.

let {AsyncResource} = require('async_hooks');

let cb = AsyncResource.bind(onData);
cb('foo');

function onData(arg) {
	console.log(arg); //undefined
}

[Flarna]

The first argument passed to the bound function is this in the called function.
Try the following:

let {AsyncResource} = require('async_hooks');

function onData(arg) {
	console.log(this, arg); // foo bar
}

let cb = AsyncResource.bind(onData);
cb('foo', 'bar');

[targos]

Then that's a documentation issue

[lroal]

The first argument passed to the bound function is this in the called function.
Try the following:

let {AsyncResource} = require('async_hooks');

function onData(arg) {
	console.log(this, arg); // foo bar
}

let cb = AsyncResource.bind(onData);
cb('foo', 'bar');

It prints: [String: 'foo'] bar

The behaviour is very surprising. Why do we need to involve the "this" key word ?
You would expect the bind method too act as as simple proxy for callback. Not intertwined with "this".
I think it would be better if the method is consistent with signature of domain.bind . The intention is that async_hooks should replace the domain - so staying close to the orignal api is a good idea.

[Flarna]

The API is just a wrapper around asyncResource.runInAsyncScope which allows to pass this similar as Reflect.apply().
Allowing user to specify the target is helpful to use it with class methods.

But it seems reusing the name bind causes confusions as one could assume that it acts similar as Function.bind().

@jasnell as author of #34574 any thoughts regarding this?

[jasnell]

Definitely a documentation issue.

So, the correct use of the function is:

const ar = new AsyncResource('foo')

const fn = ar.bind((...args) => console.log(this, args));
fn({}, 1, 2, 3); // where the {} is thisArg

We could modify the API to accept the additional this argument to help avoid the confusion.

const ar = new AsyncResource('foo')

const fn = ar.bind((...args) => console.log(this, args), {}); // pass the additional this arg
fn(1, 2, 3);

Would make for a good first contribution to do both the doc update (to add an example of correct usage) and add the additional argument.