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Add scanAsync to Akka Streams, similar to scan but taking a Future (#21553)

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* Add comprehensive tests
* Add documentation

* Damn comma after rebase

* Add documentation for foldAsync and scanAsync

* Rename aggreator and aggreating to current

* Remove out availability check

* Revert removing out and some refactors

* Formatting documentation

* Use after instead of Promise in test

* Use package reference to after and some refactoring
This commit is contained in:
Mateus Dubiela Oliveira 2016-10-17 12:43:11 -02:00 • committed by Patrik Nordwall
parent 60bea26171
commit c3abde60d5
10 changed files with 458 additions and 4 deletions
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26
akka-stream/src/main/scala/akka/stream/javadsl/Source.scala
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@ -1243,6 +1243,32 @@ final class Source[+Out, +Mat](delegate: scaladsl.Source[Out, Mat]) extends Grap
def scan[T](zero: T)(f: function.Function2[T, Out, T]): javadsl.Source[T, Mat] =
new Source(delegate.scan(zero)(f.apply))
/**
* Similar to `scan` but with a asynchronous function,
* emits its current value which starts at `zero` and then
* applies the current and next value to the given function `f`,
* emitting a `Future` that resolves to the next current value.
*
* If the function `f` throws an exception and the supervision decision is
* [[akka.stream.Supervision.Restart]] current value starts at `zero` again
* the stream will continue.
*
* If the function `f` throws an exception and the supervision decision is
* [[akka.stream.Supervision.Resume]] current value starts at the previous
* current value, or zero when it doesn't have one, and the stream will continue.
*
* '''Emits when''' the future returned by f` completes
*
* '''Backpressures when''' downstream backpressures
*
* '''Completes when''' upstream completes and the last future returned by `f` completes
*
* '''Cancels when''' downstream cancels
*
* See also [[FlowOps.scan]]
*/
def scanAsync[T](zero: T)(f: function.Function2[T, Out, CompletionStage[T]]): javadsl.Source[T, Mat] =
new Source(delegate.scanAsync(zero) { (out, in) ⇒ f(out, in).toScala })
/**
* Similar to `scan` but only emits its result when the upstream completes,
* after which it also completes. Applies the given function `f` towards its current and next value,