Introduces eager cancellation for divertTo

* and updates Partition to support this behavior
* not adding Partition.apply overload due to type inference issues, use constructor instead

akka-docs/src/main/paradox/stream/stages-overview.md

@@ -1085,6 +1085,8 @@ Each upstream element will either be diverted to the given sink, or the downstre
 
 **completes** when upstream completes and no output is pending
 
+**cancels** when any of the downstreams cancel
+
 ---------------------------------------------------------------
 
 <br/>

akka-stream-tests/src/test/scala/akka/stream/scaladsl/GraphPartitionSpec.scala

@@ -89,13 +89,13 @@ class GraphPartitionSpec extends StreamSpec {
       c2.expectComplete()
     }
 
-    "cancel upstream when downstreams cancel" in assertAllStagesStopped {
+    "cancel upstream when all downstreams cancel if eagerCancel is false" in assertAllStagesStopped {
       val p1 = TestPublisher.probe[Int]()
       val c1 = TestSubscriber.probe[Int]()
       val c2 = TestSubscriber.probe[Int]()
 
       RunnableGraph.fromGraph(GraphDSL.create() { implicit b ⇒
-        val partition = b.add(Partition[Int](2, { case l if l < 6 ⇒ 0; case _ ⇒ 1 }))
+        val partition = b.add(new Partition[Int](2, { case l if l < 6 ⇒ 0; case _ ⇒ 1 }, false))
         Source.fromPublisher(p1.getPublisher) ~> partition.in
         partition.out(0) ~> Flow[Int].buffer(16, OverflowStrategy.backpressure) ~> Sink.fromSubscriber(c1)
         partition.out(1) ~> Flow[Int].buffer(16, OverflowStrategy.backpressure) ~> Sink.fromSubscriber(c2)
@@ -114,10 +114,38 @@ class GraphPartitionSpec extends StreamSpec {
       p1Sub.sendNext(2)
       c1.expectNext(2)
       sub1.cancel()
+      p1Sub.sendNext(9)
+      c2.expectNext(9)
       sub2.cancel()
       p1Sub.expectCancellation()
     }
 
+    "cancel upstream when any downstream cancel if eagerCancel is true" in assertAllStagesStopped {
+      val p1 = TestPublisher.probe[Int]()
+      val c1 = TestSubscriber.probe[Int]()
+      val c2 = TestSubscriber.probe[Int]()
+
+      RunnableGraph.fromGraph(GraphDSL.create() { implicit b ⇒
+        val partition = b.add(new Partition[Int](2, { case l if l < 6 ⇒ 0; case _ ⇒ 1 }, true))
+        Source.fromPublisher(p1.getPublisher) ~> partition.in
+        partition.out(0) ~> Flow[Int].buffer(16, OverflowStrategy.backpressure) ~> Sink.fromSubscriber(c1)
+        partition.out(1) ~> Flow[Int].buffer(16, OverflowStrategy.backpressure) ~> Sink.fromSubscriber(c2)
+        ClosedShape
+      }).run()
+
+      val p1Sub = p1.expectSubscription()
+      val sub1 = c1.expectSubscription()
+      val sub2 = c2.expectSubscription()
+      sub1.request(3)
+      sub2.request(3)
+      p1Sub.sendNext(1)
+      p1Sub.sendNext(8)
+      c1.expectNext(1)
+      c2.expectNext(8)
+      sub1.cancel()
+      p1Sub.expectCancellation()
+    }
+
     "work with merge" in assertAllStagesStopped {
       val s = Sink.seq[Int]
       val input = Set(5, 2, 9, 1, 1, 1, 10)
@@ -190,4 +218,16 @@ class GraphPartitionSpec extends StreamSpec {
     odd.expectComplete()
     even.expectComplete()
   }
+
+  "divertTo must cancel when any of the downstreams cancel" in assertAllStagesStopped {
+    val pub = TestPublisher.probe[Int]()
+    val odd = TestSubscriber.probe[Int]()
+    val even = TestSubscriber.probe[Int]()
+    Source.fromPublisher(pub.getPublisher).divertTo(Sink.fromSubscriber(odd), _ % 2 != 0).to(Sink.fromSubscriber(even)).run()
+    even.request(1)
+    pub.sendNext(2)
+    even.expectNext(2)
+    odd.cancel()
+    pub.expectCancellation()
+  }
 }

akka-stream/src/main/scala/akka/stream/javadsl/Flow.scala

@@ -1705,7 +1705,7 @@ final class Flow[-In, +Out, +Mat](delegate: scaladsl.Flow[In, Out, Mat]) extends
    *
    * '''Completes when''' upstream completes and no output is pending
    *
-   * '''Cancels when''' when all downstreams cancel
+   * '''Cancels when''' any of the downstreams cancel
    */
   def divertTo(that: Graph[SinkShape[Out], _], when: function.Predicate[Out]): javadsl.Flow[In, Out, Mat] =
     new Flow(delegate.divertTo(that, when.test))

akka-stream/src/main/scala/akka/stream/javadsl/Graph.scala

@@ -197,26 +197,48 @@ object Broadcast {
  * '''Completes when''' upstream completes
  *
  * '''Cancels when'''
- *   when one of the downstreams cancel
+ *   when any (eagerCancel=true) or all (eagerCancel=false) of the downstreams cancel
  */
 object Partition {
   /**
-   * Create a new `Partition` stage with the specified input type.
+   * Create a new `Partition` stage with the specified input type, `eagerCancel` is `false`.
    *
    * @param outputCount number of output ports
    * @param partitioner function deciding which output each element will be targeted
    */
   def create[T](outputCount: Int, partitioner: function.Function[T, Integer]): Graph[UniformFanOutShape[T, T], NotUsed] =
-    scaladsl.Partition(outputCount, partitioner = (t: T) ⇒ partitioner.apply(t))
+    new scaladsl.Partition(outputCount, partitioner.apply)
 
   /**
    * Create a new `Partition` stage with the specified input type.
    *
    * @param outputCount number of output ports
    * @param partitioner function deciding which output each element will be targeted
+   * @param eagerCancel this stage cancels, when any (true) or all (false) of the downstreams cancel
+   */
+  def create[T](outputCount: Int, partitioner: function.Function[T, Integer], eagerCancel: Boolean): Graph[UniformFanOutShape[T, T], NotUsed] =
+    new scaladsl.Partition(outputCount, partitioner.apply, eagerCancel)
+
+  /**
+   * Create a new `Partition` stage with the specified input type, `eagerCancel` is `false`.
+   *
+   * @param clazz a type hint for this method
+   * @param outputCount number of output ports
+   * @param partitioner function deciding which output each element will be targeted
    */
   def create[T](clazz: Class[T], outputCount: Int, partitioner: function.Function[T, Integer]): Graph[UniformFanOutShape[T, T], NotUsed] =
-    create(outputCount, partitioner)
+    new scaladsl.Partition(outputCount, partitioner.apply)
+
+  /**
+   * Create a new `Partition` stage with the specified input type.
+   *
+   * @param clazz a type hint for this method
+   * @param outputCount number of output ports
+   * @param partitioner function deciding which output each element will be targeted
+   * @param eagerCancel this stage cancels, when any (true) or all (false) of the downstreams cancel
+   */
+  def create[T](clazz: Class[T], outputCount: Int, partitioner: function.Function[T, Integer], eagerCancel: Boolean): Graph[UniformFanOutShape[T, T], NotUsed] =
+    new scaladsl.Partition(outputCount, partitioner.apply, eagerCancel)
 
 }
 

akka-stream/src/main/scala/akka/stream/javadsl/Source.scala

@@ -761,7 +761,7 @@ final class Source[+Out, +Mat](delegate: scaladsl.Source[Out, Mat]) extends Grap
    *
    * '''Completes when''' upstream completes and no output is pending
    *
-   * '''Cancels when''' when all downstreams cancel
+   * '''Cancels when''' any of the downstreams cancel
    */
   def divertTo(that: Graph[SinkShape[Out], _], when: function.Predicate[Out]): javadsl.Source[Out, Mat] =
     new Source(delegate.divertTo(that, when.test))

akka-stream/src/main/scala/akka/stream/javadsl/SubFlow.scala

@@ -1160,7 +1160,7 @@ class SubFlow[-In, +Out, +Mat](delegate: scaladsl.SubFlow[Out, Mat, scaladsl.Flo
    *
    * '''Completes when''' upstream completes and no output is pending
    *
-   * '''Cancels when''' when all downstreams cancel
+   * '''Cancels when''' any of the downstreams cancel
    */
   def divertTo(that: Graph[SinkShape[Out], _], when: function.Predicate[Out]): SubFlow[In, Out, Mat] =
     new SubFlow(delegate.divertTo(that, when.test))

akka-stream/src/main/scala/akka/stream/javadsl/SubSource.scala

@@ -1152,7 +1152,7 @@ class SubSource[+Out, +Mat](delegate: scaladsl.SubFlow[Out, Mat, scaladsl.Source
    *
    * '''Completes when''' upstream completes and no output is pending
    *
-   * '''Cancels when''' when all downstreams cancel
+   * '''Cancels when''' any of the downstreams cancel
    */
   def divertTo(that: Graph[SinkShape[Out], _], when: function.Predicate[Out]): SubSource[Out, Mat] =
     new SubSource(delegate.divertTo(that, when.test))

akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala

@@ -2308,14 +2308,14 @@ trait FlowOps[+Out, +Mat] {
    *
    * '''Completes when''' upstream completes and no output is pending
    *
-   * '''Cancels when''' when all downstreams cancel
+   * '''Cancels when''' any of the downstreams cancel
    */
   def divertTo(that: Graph[SinkShape[Out], _], when: Out ⇒ Boolean): Repr[Out] = via(divertToGraph(that, when))
 
   protected def divertToGraph[M](that: Graph[SinkShape[Out], M], when: Out ⇒ Boolean): Graph[FlowShape[Out @uncheckedVariance, Out], M] =
     GraphDSL.create(that) { implicit b ⇒ r ⇒
       import GraphDSL.Implicits._
-      val partition = b.add(Partition[Out](2, out ⇒ if (when(out)) 1 else 0))
+      val partition = b.add(new Partition[Out](2, out ⇒ if (when(out)) 1 else 0, true))
       partition.out(1) ~> r
       FlowShape(partition.in, partition.out(0))
     }
@@ -2335,7 +2335,6 @@ trait FlowOps[+Out, +Mat] {
    * asynchronously.
    */
   def async: Repr[Out]
-
 }
 
 /**

akka-stream/src/main/scala/akka/stream/scaladsl/Graph.scala

@@ -628,16 +628,19 @@ final class Broadcast[T](val outputPorts: Int, val eagerCancel: Boolean) extends
 }
 
 object Partition {
-
+  // FIXME make `PartitionOutOfBoundsException` a `final` class when possible
   case class PartitionOutOfBoundsException(msg: String) extends IndexOutOfBoundsException(msg) with NoStackTrace
 
   /**
-   * Create a new `Partition` stage with the specified input type.
+   * Create a new `Partition` stage with the specified input type. This method sets `eagerCancel` to `false`.
+   * To specify a different value for the `eagerCancel` parameter, then instantiate Partition using the constructor.
+   *
+   * If `eagerCancel` is true, partition cancels upstream if any of its downstreams cancel, if false, when all have cancelled.
    *
    * @param outputPorts number of output ports
    * @param partitioner function deciding which output each element will be targeted
-   */
+   */ // FIXME BC add `eagerCancel: Boolean = false` parameter
-  def apply[T](outputPorts: Int, partitioner: T ⇒ Int): Partition[T] = new Partition(outputPorts, partitioner)
+  def apply[T](outputPorts: Int, partitioner: T ⇒ Int): Partition[T] = new Partition(outputPorts, partitioner, false)
 }
 
 /**
@@ -650,14 +653,19 @@ object Partition {
  *
  * '''Completes when''' upstream completes and no output is pending
  *
- * '''Cancels when'''
+ * '''Cancels when''' all downstreams have cancelled (eagerCancel=false) or one downstream cancels (eagerCancel=true)
- *   when all downstreams cancel
  */
 
-final class Partition[T](val outputPorts: Int, val partitioner: T ⇒ Int) extends GraphStage[UniformFanOutShape[T, T]] {
+final class Partition[T](val outputPorts: Int, val partitioner: T ⇒ Int, val eagerCancel: Boolean) extends GraphStage[UniformFanOutShape[T, T]] {
+
+  /**
+   * Sets `eagerCancel` to `false`.
+   */
+  @deprecated("Use the constructor which also specifies the `eagerCancel` parameter")
+  def this(outputPorts: Int, partitioner: T ⇒ Int) = this(outputPorts, partitioner, false)
 
   val in: Inlet[T] = Inlet[T]("Partition.in")
-  val out: Seq[Outlet[T]] = Seq.tabulate(outputPorts)(i ⇒ Outlet[T]("Partition.out" + i))
+  val out: Seq[Outlet[T]] = Seq.tabulate(outputPorts)(i ⇒ Outlet[T]("Partition.out" + i)) // FIXME BC make this immutable.IndexedSeq as type + Vector as concret impl
   override val shape: UniformFanOutShape[T, T] = UniformFanOutShape[T, T](in, out: _*)
 
   override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = new GraphStageLogic(shape) with InHandler {
@@ -690,11 +698,10 @@ final class Partition[T](val outputPorts: Int, val partitioner: T ⇒ Int) exten
 
     setHandler(in, this)
 
-    out.zipWithIndex.foreach {
+    out.iterator.zipWithIndex.foreach {
       case (o, idx) ⇒
         setHandler(o, new OutHandler {
           override def onPull() = {
-
             if (outPendingElem != null) {
               val elem = outPendingElem.asInstanceOf[T]
               if (idx == outPendingIdx) {
@@ -711,7 +718,9 @@ final class Partition[T](val outputPorts: Int, val partitioner: T ⇒ Int) exten
               pull(in)
           }
 
-          override def onDownstreamFinish(): Unit = {
+          override def onDownstreamFinish(): Unit =
+            if (eagerCancel) completeStage()
+            else {
               downstreamRunning -= 1
               if (downstreamRunning == 0)
                 completeStage()
@@ -728,7 +737,6 @@ final class Partition[T](val outputPorts: Int, val partitioner: T ⇒ Int) exten
   }
 
   override def toString = s"Partition($outputPorts)"
-
 }
 
 object Balance {