Koa: ES7 Async/Await question

[perrin4869]

Not sure if this is the right place to ask this question, and if it is not, then feel free to close the issue :)

Doing some research into ES7 async/await, I came across this article: https://spion.github.io/posts/es7-async-await-step-in-the-wrong-direction.html

Refering to the section, 'Loss of generality and power', I was wondering, is the argument in that article relevant to [email protected]? It does seem that generators, as used in [email protected] are much stronger than async functions, although the async/await pattern does seem to satisfy most use cases

[fl0w]

To be fair; avoid using async/await and you've got your "generality" back. There's nothing forcing you to use async/await in koa@2.

const Koa = require('koa')
const app = new Koa()
app.use((ctx, next) => {
  ctx.state.myState = 'Hello '
  next()
})
app.use(ctx => {
  ctx.body = ctx.state.myState + ' World'
})

[gyson]

@fl0w you need return next() in your example.

[fl0w]

@gyson yes, that's the intent. But this was a counter argument. The question was about if the syntax is to declarative; I was illustrating that this has nothing to do with koas v2 implementation. A middleware stack can be run as a function chain.

Obviously not recommended; but somewhat mutes OP's concern.

[perrin4869]

Hm... but what about this: https://github.com/koajs/koa/blob/v2.x/lib/application.js#L103
This means that if you cannot supply your own run engine, as per the article above anymore. What if I want to use bluebird Promise.coroutine for example? Or my own custom implementation?

[fl0w]

@perrin4869 https://github.com/koajs/koa/pull/683/files

And what you're talking about is scope. You can't cover all needs and all use-cases now and in the future: "What if I wanted to use express middleware in koa@1, and not use generators/yield?". It's not koa's concern.

[PlasmaPower]

You can extend the Application class to override callback and use.

[jonathanong]

i'm not sure what the article is saying (i only skimmed it). you could always do something like:

app.use(Bluebird.coroutine(function * (ctx, next) {
  yield next()
})

and replace Bluebird.coroutine() with whatever engine you want.

[jonathanong]

closing for now!