.await has wrong type?

Summary

I think the TypeScript type for Most.await is problematic. Consider this code:

  return Most
    .periodic(queueSettings.WaitTimeSeconds / 1000)
    .map(() => pull(settings.queue, queueSettings))
    .await() // should be awaitPromises but TypeScript definition doesn't accept that yet...
    .concatMap((data: AWS.SQS.ReceiveMessageResult) =>
      Most.from(data.messages.map(process)),
    )
    .multicast()

Expected result

It should return a Stream<Change>.

Actual Result

It instead returns a Stream<{}>. This is because of await which has a return value of Stream<{}>.

Versions

• most.js: <version> ^1.4.0

I will try to come back with a PR or failing that a simplified repro.

[gcanti]

there’s no way in TS to express “this method can only be called on a this whose value type is Promise<B>”

Maybe this can be helpful

declare class Stream<A> {
  map<B>(f: (a: A) => B): Stream<B>
  // you can define a type annotation for this
  await<B>(this: Stream<Promise<B>>): Stream<B>
  // etc...
}

new Stream<number>().await() // error
new Stream<Promise<number>>().await() // ok
new Stream<string>().map(s => Promise.resolve(s.length)).await() // ok

[briancavalier]

@jasonkuhrt this just landed in most 1.6.1. Thanks again for raising the issue, and thanks @gcanti for the solution.