>why not just `await` as already is, but supporting an >iterable / array of promises, as `Promise.all` already does
`await` can already accept a non-promise, so I believe that'd be breaking syntax if `Array.prototype.then` is set. It also requires collecting the promises in an array, which is what the proposed syntax is trying to avoid. On Thu, Nov 21, 2019 at 2:41 AM Jacob Bloom <[email protected]> wrote: > > >Just FYI, I previously suggested a couple things substantially more > >flexible than this > > Ah, thank you for bringing those proposals to my attention. I looked > through the archives for relevant discussions but I must've missed > them. > > It seems like we converged on a similar syntax for what you called > "merging," and the idea that there ought to be a separate syntax for > iteration. I don't know whether that means that this is the right > solution or just the most obvious one, but either way it's encouraging > to know that other people have the same difficulties with the current > syntax and are thinking about the problem. > > >from my experience, committee members are in general > >very hesitant to add syntax for anything that doesn't pay for > >itself well > > Yeah, I figured the bar would be high for new syntax. I've run into > the awkwardness of dealing with distinct parallel tasks several times, > and a few of the people I discussed it with were in the same boat, so > I wrote up this proposal thinking it might have a wide appeal. The > proposed syntax desugars via a relatively simple transformation but > encourages developers to reason about the problem in a completely > different way that I'd argue is more intuitive. Whether the committee > agrees and thinks it justifies a new syntax remains to be seen, but > either way I'm excited to see where this discussion goes (whether it > leads to the proposed syntax, to some other syntax, or to somewhere > else entirely). > > As a side note: thank you to everyone for the thoughtful questions and > responses, I had no idea what to expect from this thread and it's gone > better than I could've hoped for. Thank you for not immediately > shooting down a proposal that looks similar to other proposals before > it. > > On Wed, Nov 20, 2019 at 7:36 PM Isiah Meadows <[email protected]> > wrote: > > > > Just FYI, I previously suggested a couple things substantially more > > flexible than this [1] [2] (originated from this [3]), and it mostly > > fell flat due to being highly premature. Anything exclusive to > > promises is unlikely to win as library methods exist for basically all > > use cases and from my experience, committee members are in general > > very hesitant to add syntax for anything that doesn't pay for itself > > well. Similar questions have come up a few times in the past, too, and > > I've commented on two of them. [4] [5] > > > > If anything, I don't feel we know the problem space well enough, and > > the language lacks the primitives needed to really dig into it. (This > > is why I came up with my generator forking strawman. [6]) > > > > [1]: https://github.com/isiahmeadows/non-linear-proposal > > [2]: https://github.com/isiahmeadows/lifted-pipeline-strawman > > [3]: > > https://esdiscuss.org/topic/observable-promise-parallel-control-flow-proposal > > [4]: https://esdiscuss.org/topic/stream-async-await > > [5]: > > https://esdiscuss.org/topic/improved-syntax-for-observable-mapping-and-subscribing > > [6]: https://github.com/isiahmeadows/proposal-generator-fork > > > > ----- > > > > Isiah Meadows > > [email protected] > > www.isiahmeadows.com > > > > On Wed, Nov 20, 2019 at 6:16 PM Jacob Bloom <[email protected]> > > wrote: > > > > > > ...strike that, I misread the "but that still waits for the async > > > functions to complete" part. So what you're proposing is that > > > everything functions normally inside the curly braces, but execution > > > doesn't continue until all promises have resolved? So your example > > > would work essentially like this: > > > > > > ```javascript > > > const x = doSomethingAsync(); > > > const y = doSomethingElseAsync(); > > > await x, await y; > > > // all promises are resolved by now, but > > > // still need to use await to unbox the values > > > someFunction(await x, await y); > > > ``` > > > > > > On Wed, Nov 20, 2019 at 3:28 PM Jacob Bloom <[email protected]> > > > wrote: > > > > > > > > >Maybe if you drop the "await" in your example: > > > > > > > > > >```javascript > > > > >await.all { > > > > > const x = doSomethingAsync(); > > > > > //x is just the promise here > > > > >} > > > > >``` > > > > > > > > > >...but that still waits for the async functions to complete, I think > > > > >it would > > > > >cause fewer bugs and would seem to still satisfy the motivation? > > > > > > > > It doesn't seem like the `await.all` block is doing anything in that > > > > case. That code seems equivalent to this: > > > > > > > > ```javascript > > > > const x = doSomethingAsync(); > > > > myFunction(await x) > > > > ``` > > > > > > > > >```javascript > > > > >await.all { > > > > > const x = await doSomethingAsync(); > > > > > //x is still undefined here! > > > > >} > > > > >``` > > > > > > > > You bring up a good point about scoping and race conditions. It's a > > > > little tricky since the curly braces create a block scope but none of > > > > the parallel statements should be allowed to access each-other's > > > > variables, it's almost like each statement should have its own scope. > > > > Maybe it'd be better to have a syntax that ensures a set of curly > > > > braces for each parallel task? Async do-expressions could be a good > > > > solution (assuming they'd work kind of like an async IIFE): > > > > > > > > ```javascript > > > > async function initialize() { > > > > let foo, bar, baz; > > > > await Promise.all([ > > > > async do { foo = (await request('foo.json')).data }, > > > > async do { bar = (await request('bar.json')).data }, > > > > async do { baz = (await request('baz.json')).data }, > > > > ]); > > > > render(foo, bar, baz); > > > > } > > > > ``` > > > > > > > > (this is also a less drastic syntax change that piggybacks on an > > > > existing proposal) > > > > > > > > On Wed, Nov 20, 2019 at 11:50 AM Bergi <[email protected]> wrote: > > > > > > > > > > Hello! > > > > > > > > > > > This [current] structure is also just fundamentally different from > > > > > > working > > > > > > serially in async/await and it forces you to reason about the > > > > > > problem > > > > > > in a specific way. This doesn't appear to be a conscious decision to > > > > > > force good code practices > > > > > > > > > > Actually I'd argue that it is. Doing stuff concurrently *is* > > > > > fundamentally different from doing it serially, and should be reasoned > > > > > about every time you use it. > > > > > > > > > > kind regards, > > > > > Bergi > > > > > _______________________________________________ > > > > > es-discuss mailing list > > > > > [email protected] > > > > > https://mail.mozilla.org/listinfo/es-discuss > > > _______________________________________________ > > > es-discuss mailing list > > > [email protected] > > > https://mail.mozilla.org/listinfo/es-discuss _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
