[Suggestions] A new way to represent `Coroutine` + returns.future `@future` decorator ?

[denis-migdal]

Hi,

Two suggestions :

1/ A new way to represent Coroutine

I recently discovered a little h4ck to create JS async function that are executed only when awaited:

class Coroutine extends Promise { // required if JS do instanceof Promise()
    /*
    constructor( compute ) {
          super(...);
          this.#compute = compute;
    }
    */
    then(...args) {
        console.warn("start computations") // the computations to perform.
        // this.#compute();
        this.then = super.then;
        return super.then(...args);
    }
}
let c = new Coroutine()
await c; // prints "start computations"

This could be useful if pyobj2jsobj converted <coroutine> into an instance of this class, enabling to await a corouting in JS:

from browser import window

async def foo():
    print("?")

window.f1 = foo()

// in JS : await window.f1

2/ returns.future @future decorator

The returns.future python package provides 2 decorators @future and @future-safe:
https://pypi.org/project/returns/
https://returns.readthedocs.io/en/latest/pages/future.html#returns.future.Future

@future # starts execution directly when called.
async def test(arg: int) -> float:
    return arg / 2

I though it could be quite useful if it was included to Brython's stdlib.