Add `Promise` style API support

[JounQin]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and discussions and couldn’t find anything (or linked relevant results below)

Problem

It still use callback style API

Current solutions

N/A

Proposed solutions

Migrate to mixed support for callback + Promise style at the same time by checking typeof callback === 'function'

[remcohaszing]

I like this, but IMO we might as well drop callback support then.

[JounQin]

I like this, but IMO we might as well drop callback support then.

Yeah, but I don't think BREAKING CHANGES are required now, so I personally prefer compatible way, and maybe in next major when we drop Node 16, etc.

[ChristianMurphy]

Taking a step back, what problem are you trying to solve?

• Are you interfacing with a promise only library?
• Something else?

Node does have a wrapper to make callback into promises https://nodejs.org/api/util.html#utilpromisifyoriginal
Would that work?

[JounQin]

I'm not resolving any problems, I'm just proposing to get rid of callback style APIs.

[ChristianMurphy]

So usage of the API would need top level await?
Wouldn't that re-break requiring esm from commonjs?
https://nodejs.org/api/modules.html#loading-ecmascript-modules-using-require

[JounQin]

So usage of the API would need top level await?

Why? it doesn't. I'm just saying change class methods like engin#load/Configuration#load, etc.

[wooorm]

I don’t think that we need to break things for no reason?

Callbacks are used because they are useful for watch mode: https://github.com/unifiedjs/unified-args/blob/main/lib/index.js.

If we would break to use promises, users would still need to write callbacks, just two: engine().then(callback1, callback2)?

[ChristianMurphy]

Why? it doesn't.

The main API?
https://github.com/unifiedjs/unified-engine?tab=readme-ov-file#use

The whole thing expects a done callback.
Making that a promise would require top level await.

[wooorm]

Making that a promise would require top level await.

Someone could use engine inside a function right?

async function someFunction() {
  console.log(await engine(options))
}

Or, callbacks:

function someFunction() {
  engine(options).then(function (stuff) {
    console.log(stuff)
  })
}

[JounQin]

That's why I'm saying support typeof callback === 'function' without any breaking, callback can still be used if preferred?

[github-actions]

Hi! This was closed. Team: If this was fixed, please add phase/solved. Otherwise, please add one of the no/* labels.