Implications of adopting async await with es7

[calebboyd]

It's looking like koa might adopt async awaitsyntax coming in es7. And its implementation (specifically the way middleware are composed) raises some questions.

As the proposal stands, the async modifier is set indicating the function returns a Promise; explicitly or by awaiting one, then returning a value.

My question comes from the observation that next is not a promise -- how then, can it be await-ed?
Supposing it were a promise. The nature of it being named next implies that the upstream has already occurred which should not be true until after await next.

A solution would be to alter the api such that middleware must invoke next() which imo gives more control to whoever is implementing the middleware

I could be completely wrong and perhaps not understand the direction koa is going. Is koa going to stick with generators? It would seem the api is designed specifically for them.

[jonathanong]

#415

if you look at https://github.com/thenables/composition, it is done by simply adding a .then() function to next, making it a "lazy promise".

[calebboyd]

My feedback and questions received no reply in #415 :/. I looked at composition and that raised the second question/statement

Supposing it were a promise. The nature of it being named next implies that the upstream has already occurred which should not be true until after await next.

I guess I'm saying it is non-intuitive that it does indeed call the upstream of the next middleware

[jonathanong]

¯\_(ツ)_/¯ this is the path we've chosen. i guess it is confusing if you're coming from promise-land, not generator-land

[calebboyd]

Sounds good