Pipeline operator doesnt await properly

[dacz]

await in pipeline doesn't translate to working code as described in specs.

Input Code

const f1 = async x => x + 1;
const f2 = async x => Promise.resolve(x + 1);

// this is ok
const runOk = async () =>
  5 |> async(_) => await f1(_) |> async (_) => await f2(_);

runOk().then(v => console.log('runOk returns:', v));

// this will not await fir the results
const runFail = async () =>
  5 |> await f1 |> await f2;

runFail().then(v => console.log('runFail returns:', v))

repl

babel v7.0.0.-beta39

Expected Behavior

translates to

...
return _ref2 = (_3 = 5, (await f1)(_3)), (await f2)(_ref2);
...

should translate to

return _ref2 = (_3 = 5, (await f1(_3)), await f2(_ref2);

[babel-bot]

Hey @dacz! We really appreciate you taking the time to report an issue. The collaborators
on this project attempt to help as many people as possible, but we're a limited number of volunteers,
so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack
community that typically always has someone willing to help. You can sign-up here
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[mAAdhaTTah]

I'd be happy to take a look at this after we land #7458.

[nicolo-ribaudo]

This will be fixed by #7154

[dacz]

@nicolo-ribaudo thanks. Do you have any idea when it will be released? You requested changes in #7154 in Jan and it is kind of stalled since then and with conflicts with master.

[mAAdhaTTah]

So we're going to ban await in the basic, "minimal proposal" spec here: tc39/proposal-pipeline-operator#108 and solve await in each of the proposals we're working on currently working on. This is not going to be the final semantics of pipeline in any of the proposals, given the ambiguity between whether x |> await f becomes await f(x) or (await f)(x).

[dacz]

@mAAdhaTTah Thank for the note. I've read the conversations but it's not clear to me.

Pipeline operator (as part of the stage-1) will work but await will NOT be part of it (will throw). There will be (probably) two different plugins that will add the await functionality (as f# style or smart style) or one that will use flags to signalize the used style.

Do I understand it well? Thanks a lot.

[mAAdhaTTah]

Yes, although not "probably"; those two different plugins are in progress already, representing two different proposals for the pipeline operator. We're doing this to solicit feedback from the community on them.

Edit: Excuse me, one babel plugin, flags for the various "modes".

[mAAdhaTTah]

I believe we can close this, as we banned await in the minimal and are working on implementing await properly in each of the proposals.

[js-choi]

I dunno; maybe it’d be good to keep it open until we finish actually implementing it in them. It’s “in progress”, at least. But either way is probably fine.

[thiagoarrais]

Given the current incarnation of the proposals, I think this may be closed with a WONTFIX.

IIRC, this input code is a syntax error both in smart as in f#:

 5 |> await f1 |> await f2;

And if we put parentheses around the await clause, f# will translate it to:

return _ref2 = (_3 = 5, (await f1)(_3)), (await f2)(_ref2);

Which doesn't seem to be the intention of the OP.