fn.name and fn.length?

[jprichardson]

Piggybacking from this comment... jprichardson/node-fs-extra#403 (comment)

Why wouldn't you want to set fn.name and fn.length? Stated another way, why wouldn't you want to take the implementation from https://github.com/paulmillr/micro-promisify/blob/600daee25abc75af3cef8145ef6eb55aafdd2d54/index.js#L11? I'm not saying that implementation is correct, I'm just interested in your reasoning.

[RyanZim]

OK, perhaps I wasn't clear enough. I do want to set fn.name. I'll be fixing that as soon as I can.

---

Regarding fn.length: Suppose we have this function:

function foo (a, b, callback) { ... }

We want to universalify it:

const newFoo = universalify.fromCallback(foo)

Now, we can use it like this:

newFoo(1, 2)
.then(..)
.catch(..)

or like this:

newFoo(1, 2, (err, res) => {
  // Do something
})

Note that in the first example, we called newFoo with 2 arguments. In the second example, we called it with 3.

micro-promisify doesn't support calling the transformed functions with callbacks, so it sets fn.length to Math.max(0, fn.length - 1). This logic doesn't apply to universalify, since it's still possible to call the function with a callback.

However, if we keep the old fn.length value, this might be confusing for promise users. Also, should functions passed to fromPromise have their length bumped by 1 or not?

Therefore, I was thinking of just leaving fn.length unset.

[jprichardson]

Ah, everything makes sense. Got it.

[RyanZim]

OK, I'll fix name later today, then we can move forward.