Decorators for generators?

[dead-claudia]

This is the one part I was surprised didn't exist. Every other possibility I can think of is covered with this proposal, but I think generators might have been overlooked.

I have already come across a problem where I needed this functionality, and I ran into issues.

Is there any reason generators shouldn't be decorated?

[dead-claudia]

FWIW, here's my use case:

function checkCallable(desc) {
    const original = desc.value
    desc.value = function (f) {
        assertCallable(f, 'f')
        return original.apply(this, arguments)
    }
}

function wrap(desc) {
    const original = desc.value
    desc.value = function () {
        return new Wrapper(original.apply(this, arguments))
    }
}

class Wrapper {
    // ...

    @checkCallable @wrap *map(f) {
        let index = 0
        for (const entry of this) {
            yield f(entry, index++)
        }
    }

    @checkCallable @wrap *filter(f) {
        let index = 0
        for (const entry of self) {
            if (f(entry, index++)) {
                yield entry
            }
        }
    }

    // ...
}

[rosshadden]

👍 I'm surprised this didn't work already, as generators seem to work just like normal functions for everything else (like static class methods, for example).

[optikalefx]

We're making an app using KOA, and it was exciting to use decorators to give all of our methods an @verb and and @param. But it seems generator functions don't accept decorators yet. +1 for this feature.

[galenwarren]

Running into the same issue, trying to decorate generator functions in a Koa app for routing purposes. From another thread, I see this is an issue of ambiguous grammar, but that thread seems to suggest the underlying issue is resolved: https://phabricator.babeljs.io/T2014. Is there a way to get this to work now?

[dead-claudia]

@galenwarren You are correct (#34). I think the only outstanding part remaining is a PR.

[silkentrance]

Actually this should work and was never limited by the spec, but it does not due to a "bug" in babylon. See also #66.