Document how error handling works

[acjay]

How are failed futures handled? Does the whole async block just fail? Is there a way to handle individual failed awaits within one async block, or is the only solution there to nest async blocks? If that's the case, perhaps a tryAwait that returns a Try would be helpful. In any case, a couple examples in the docs would be great. Thanks

[justjoheinz]

I would also be interested in this.

[danarmak]

The code behaves as if the call to await throws the exception with which the awaited Future failed.

While await under try/catch is currently unsupported, one alternative would be to write await(future recover ...).

tryAwait would be equivalent to this simple function: def tryAwait[T](fut: Future[T]): Try[T] = await(fut map Success.apply recover PartialFunction(Failure.apply)

However, that won't work because await can't be used inside a function; a macro is needed. I'll submit a PR with that macro if you'd be interested in including tryAwait in the project.

(From what I've read of the code, most of the work will be to construct the right kind of Tryy. Why is there even a Tryy type if both implementations use scala.util.Try?)

[pkolaczk]

+1 to tryAwait at least until proper try/catch handling is supported

[acjay]

I'll submit a PR with that macro if you'd be interested in including tryAwait in the project.

This would be much appreciated!

[ebruchez]

I was playing with async/await and this is one of the first questions that popped up. So :+1: to improve this.

[ebruchez]

FWIW I used @danarmak's solution above:

await(kittens() map Success.apply recover PartialFunction(Failure.apply)) match {
  case Failure(t) ⇒ // ...
  case Success(v) ⇒ // ...
}

But a tryAwait shortcut would be good.