=str - 16467 - Updates Akka Streams to Reactive Streams 1.0.0.M3

Only failing test is for the SynchronousIterablePublisher since the TCK doesn't handle sync
publishers well (@ktoso is working to fix this for the 1.0.0.RC1)

Adds a lot of FIXMEs to make sure we fix them before we ship the final version of Akka Streams.

akka-stream-tck/src/test/scala/akka/stream/tck/AkkaPublisherVerification.scala

@@ -37,9 +37,6 @@ abstract class AkkaPublisherVerification[T](val system: ActorSystem, env: TestEn
 
   override def skipStochasticTests() = true // TODO maybe enable?
 
-  // TODO re-enable this test once 1.0.0.RC1 is released, with https://github.com/reactive-streams/reactive-streams/pull/154
-  override def spec317_mustSignalOnErrorWhenPendingAboveLongMaxValue() = notVerified("TODO Enable this test once https://github.com/reactive-streams/reactive-streams/pull/154 is merged (ETA 1.0.0.RC1)")
-
   @AfterClass
   def shutdownActorSystem(): Unit = {
     system.shutdown()

akka-stream-tck/src/test/scala/akka/stream/tck/FuturePublisherTest.scala

@@ -0,0 +1,22 @@
+/**
+ * Copyright (C) 2014 Typesafe Inc. <http://www.typesafe.com>
+ */
+package akka.stream.tck
+
+import akka.stream.scaladsl.Sink
+import akka.stream.scaladsl.Source
+import org.reactivestreams._
+
+import scala.concurrent.Promise
+
+class FuturePublisherTest extends AkkaPublisherVerification[Int] {
+
+  def createPublisher(elements: Long): Publisher[Int] = {
+    val p = Promise[Int]()
+    val pub = Source(p.future).runWith(Sink.publisher)
+    p.success(0)
+    pub
+  }
+
+  override def maxElementsFromPublisher(): Long = 1
+}

akka-stream-tck/src/test/scala/akka/stream/tck/SyncIterablePublisherTest.scala

@@ -0,0 +1,26 @@
+/**
+ * Copyright (C) 2014 Typesafe Inc. <http://www.typesafe.com>
+ */
+package akka.stream.tck
+
+import akka.stream.impl.SynchronousIterablePublisher
+
+import scala.collection.immutable
+import akka.stream.scaladsl.Sink
+import akka.stream.scaladsl.Source
+import org.reactivestreams._
+
+class SyncIterablePublisherTest extends AkkaPublisherVerification[Int] {
+
+  def createPublisher(elements: Long): Publisher[Int] = {
+    val iterable: immutable.Iterable[Int] =
+      if (elements == Long.MaxValue)
+        new immutable.Iterable[Int] { override def iterator = Iterator from 0 }
+      else
+        0 until elements.toInt
+
+    Source(SynchronousIterablePublisher(iterable, "synchronous-iterable-publisher")).runWith(Sink.publisher)
+  }
+
+  override def spec317_mustSignalOnErrorWhenPendingAboveLongMaxValue() = notVerified("RS TCK 1.0.0.M3 does not handle sync publishers well")
+}

akka-stream/src/main/scala/akka/stream/actor/ActorPublisher.scala

@@ -118,7 +118,7 @@ trait ActorPublisher[T] extends Actor {
   import akka.stream.actor.ActorPublisherMessage._
   import ActorPublisher.Internal._
   import ActorPublisherMessage._
-
+  import ReactiveStreamsCompliance._
   private val state = ActorPublisherState(context.system)
   private var subscriber: Subscriber[Any] = _
   private var demand = 0L
@@ -180,7 +180,7 @@ trait ActorPublisher[T] extends Actor {
     case Active | PreSubscriber ⇒
       if (demand > 0) {
         demand -= 1
-        subscriber.onNext(element)
+        tryOnNext(subscriber, element)
       } else
         throw new IllegalStateException(
           "onNext is not allowed when the stream has not requested elements, totalDemand was 0")
@@ -199,8 +199,8 @@ trait ActorPublisher[T] extends Actor {
     case Active | PreSubscriber ⇒
       lifecycleState = Completed
       if (subscriber ne null) // otherwise onComplete will be called when the subscription arrives
-        subscriber.onComplete()
-      subscriber = null // not used after onError
+        tryOnComplete(subscriber)
+      subscriber = null // not used after onComplete
     case Completed ⇒
       throw new IllegalStateException("onComplete must only be called once")
     case _: ErrorEmitted ⇒
@@ -216,7 +216,7 @@ trait ActorPublisher[T] extends Actor {
     case Active | PreSubscriber ⇒
       lifecycleState = ErrorEmitted(cause)
       if (subscriber ne null) // otherwise onError will be called when the subscription arrives
-        subscriber.onError(cause)
+        tryOnError(subscriber, cause)
       subscriber = null // not used after onError
     case _: ErrorEmitted ⇒
       throw new IllegalStateException("onError must only be called once")
@@ -230,13 +230,18 @@ trait ActorPublisher[T] extends Actor {
    */
   protected[akka] override def aroundReceive(receive: Receive, msg: Any): Unit = msg match {
     case Request(n) ⇒
-      demand += n
-      if (demand < 0 && lifecycleState == Active) {
-        // Long has overflown
-        val demandOverflowException = new IllegalStateException(ReactiveStreamsCompliance.TotalPendingDemandMustNotExceedLongMaxValue)
-        onError(demandOverflowException)
-      } else
+      if (n < 1) {
+        if (lifecycleState == Active)
+          onError(numberOfElementsInRequestMustBePositiveException)
+        else
           super.aroundReceive(receive, msg)
+      } else {
+        demand += n
+        if (demand < 0 && lifecycleState == Active) // Long has overflown
+          onError(totalPendingDemandMustNotExceedLongMaxValueException)
+        else
+          super.aroundReceive(receive, msg)
+      }
 
     case Subscribe(sub: Subscriber[_]) ⇒
       lifecycleState match {
@@ -245,13 +250,12 @@ trait ActorPublisher[T] extends Actor {
           subscriber = sub
           lifecycleState = Active
           sub.onSubscribe(new ActorPublisherSubscription(self))
-        case ErrorEmitted(cause) ⇒ sub.onError(cause)
-        case Completed           ⇒ sub.onComplete()
+        case ErrorEmitted(cause) ⇒ tryOnError(sub, cause)
+        case Completed           ⇒ tryOnComplete(sub)
         case Active | Canceled ⇒
-          if (subscriber == sub)
-            sub.onError(new IllegalStateException(s"ActorPublisher [$self, sub: $sub] ${ReactiveStreamsCompliance.CanNotSubscribeTheSameSubscriberMultipleTimes}"))
-          else
-            sub.onError(new IllegalStateException(s"ActorPublisher [$self] ${ReactiveStreamsCompliance.SupportsOnlyASingleSubscriber}"))
+          tryOnError(sub,
+            if (subscriber eq sub) ReactiveStreamsCompliance.canNotSubscribeTheSameSubscriberMultipleTimesException
+            else ReactiveStreamsCompliance.canNotSubscribeTheSameSubscriberMultipleTimesException)
       }
 
     case Cancel ⇒
@@ -317,7 +321,7 @@ trait ActorPublisher[T] extends Actor {
    */
   protected[akka] override def aroundPostStop(): Unit = {
     state.remove(self)
-    if (lifecycleState == Active) subscriber.onComplete()
+    if (lifecycleState == Active) tryOnComplete(subscriber)
     super.aroundPostStop()
   }
 
@@ -341,10 +345,7 @@ private[akka] class ActorPublisherSubscription[T](ref: ActorRef) extends Subscri
   import ActorPublisher._
   import ActorPublisherMessage._
 
-  override def request(n: Long): Unit = {
-    ReactiveStreamsCompliance.validateRequest(n)
-    ref ! Request(n)
-  }
+  override def request(n: Long): Unit = ref ! Request(n)
   override def cancel(): Unit = ref ! Cancel
 }
 

akka-stream/src/main/scala/akka/stream/impl/ActorProcessor.scala

@@ -129,7 +129,7 @@ private[akka] abstract class BatchingInputBuffer(val size: Int, val pump: Pump)
   }
 
   protected def completed: Actor.Receive = {
-    case OnSubscribe(subscription) ⇒ throw new IllegalStateException("Cannot subscribe shutdown subscriber")
+    case OnSubscribe(subscription) ⇒ throw new IllegalStateException("Cannot subscribe shutdown subscriber") // FIXME "shutdown subscriber"?!
   }
 
   protected def inputOnError(e: Throwable): Unit = {
@@ -177,9 +177,7 @@ private[akka] class SimpleOutputs(val actor: ActorRef, val pump: Pump) extends D
 
   def isClosed: Boolean = downstreamCompleted
 
-  protected def createSubscription(): Subscription = {
-    new ActorSubscription(actor, subscriber)
-  }
+  protected def createSubscription(): Subscription = new ActorSubscription(actor, subscriber)
 
   private def subscribePending(subscribers: Seq[Subscriber[Any]]): Unit =
     subscribers foreach { sub ⇒
@@ -201,15 +199,16 @@ private[akka] class SimpleOutputs(val actor: ActorRef, val pump: Pump) extends D
     case SubscribePending ⇒
       subscribePending(exposedPublisher.takePendingSubscribers())
     case RequestMore(subscription, elements) ⇒
-
+      if (elements < 1) {
+        cancel(ReactiveStreamsCompliance.numberOfElementsInRequestMustBePositiveException)
+      } else {
         downstreamDemand += elements
-      if (downstreamDemand < 0) {
-        // Long has overflown
-        val demandOverflowException = new IllegalStateException(ReactiveStreamsCompliance.TotalPendingDemandMustNotExceedLongMaxValue)
-        cancel(demandOverflowException)
+        if (downstreamDemand < 1) { // Long has overflown
+          cancel(ReactiveStreamsCompliance.totalPendingDemandMustNotExceedLongMaxValueException)
         }
 
-      pump.pump()
+        pump.pump() // FIXME should this be called even on overflow, sounds like a bug to me
+      }
     case Cancel(subscription) ⇒
       downstreamCompleted = true
       exposedPublisher.shutdown(Some(new ActorPublisher.NormalShutdownException))

akka-stream/src/main/scala/akka/stream/impl/ActorPublisher.scala

@@ -89,9 +89,7 @@ private[akka] class ActorPublisher[T](val impl: ActorRef) extends Publisher[T] {
  * INTERNAL API
  */
 private[akka] class ActorSubscription[T]( final val impl: ActorRef, final val subscriber: Subscriber[_ >: T]) extends Subscription {
-  override def request(elements: Long): Unit =
-    if (elements < 1) throw new IllegalArgumentException(ReactiveStreamsCompliance.NumberOfElementsInRequestMustBePositiveMsg)
-    else impl ! RequestMore(this, elements)
+  override def request(elements: Long): Unit = impl ! RequestMore(this, elements)
   override def cancel(): Unit = impl ! Cancel(this)
 }
 

akka-stream/src/main/scala/akka/stream/impl/CompletedPublishers.scala

@@ -18,7 +18,8 @@ private[akka] case object EmptyPublisher extends Publisher[Nothing] {
  * INTERNAL API
  */
 private[akka] case class ErrorPublisher(t: Throwable, name: String) extends Publisher[Nothing] {
-  override def subscribe(subscriber: Subscriber[_ >: Nothing]): Unit = subscriber.onError(t)
+  override def subscribe(subscriber: Subscriber[_ >: Nothing]): Unit =
+    ReactiveStreamsCompliance.tryOnError(subscriber, t) // FIXME how to deal with spec violations here?
   def apply[T]: Publisher[T] = this.asInstanceOf[Publisher[T]]
   override def toString: String = name
 }

akka-stream/src/main/scala/akka/stream/impl/FuturePublisher.scala

@@ -28,15 +28,13 @@ private[akka] object FuturePublisher {
 
   object FutureSubscription {
     case class Cancel(subscription: FutureSubscription)
-    case class RequestMore(subscription: FutureSubscription)
+    case class RequestMore(subscription: FutureSubscription, elements: Long)
   }
 
   class FutureSubscription(ref: ActorRef) extends Subscription {
     import akka.stream.impl.FuturePublisher.FutureSubscription._
     def cancel(): Unit = ref ! Cancel(this)
-    def request(elements: Long): Unit =
-      if (elements <= 0) throw new IllegalArgumentException(ReactiveStreamsCompliance.NumberOfElementsInRequestMustBePositiveMsg)
-      else ref ! RequestMore(this)
+    def request(elements: Long): Unit = ref ! RequestMore(this, elements)
     override def toString = "FutureSubscription"
   }
 }
@@ -44,11 +42,12 @@ private[akka] object FuturePublisher {
 /**
  * INTERNAL API
  */
-//FIXME why do we need to have an actor to drive a Future?
+// FIXME why do we need to have an actor to drive a Future?
 private[akka] class FuturePublisher(future: Future[Any], settings: MaterializerSettings) extends Actor with SoftShutdown {
   import akka.stream.impl.FuturePublisher.FutureSubscription
   import akka.stream.impl.FuturePublisher.FutureSubscription.Cancel
   import akka.stream.impl.FuturePublisher.FutureSubscription.RequestMore
+  import ReactiveStreamsCompliance._
 
   var exposedPublisher: ActorPublisher[Any] = _
   var subscribers = Map.empty[Subscriber[Any], FutureSubscription]
@@ -77,42 +76,53 @@ private[akka] class FuturePublisher(future: Future[Any], settings: MaterializerS
   def active: Receive = {
     case SubscribePending ⇒
       exposedPublisher.takePendingSubscribers() foreach registerSubscriber
-    case RequestMore(subscription) ⇒
+    case RequestMore(subscription, elements) ⇒ // FIXME we aren't tracking demand per subscription so we don't check for overflow. We should.
       if (subscriptions.contains(subscription)) {
+        if (elements < 1) {
+          val subscriber = subscriptions(subscription)
+          rejectDueToNonPositiveDemand(subscriber)
+          removeSubscriber(subscriber)
+        } else {
           subscriptionsReadyForPush += subscription
           push(subscriptions(subscription))
         }
+      }
     case Cancel(subscription) if subscriptions.contains(subscription) ⇒
       removeSubscriber(subscriptions(subscription))
     case Status.Failure(ex) ⇒
+      if (futureValue.isEmpty) {
         futureValue = Some(Failure(ex))
         pushToAll()
+      }
     case value ⇒
+      if (futureValue.isEmpty) {
         futureValue = Some(Success(value))
         pushToAll()
       }
+  }
 
   def pushToAll(): Unit = subscriptionsReadyForPush foreach { subscription ⇒ push(subscriptions(subscription)) }
 
   def push(subscriber: Subscriber[Any]): Unit = futureValue match {
     case Some(Success(value)) ⇒
-      subscriber.onNext(value)
-      subscriber.onComplete()
+
+      tryOnNext(subscriber, value)
+      tryOnComplete(subscriber)
       removeSubscriber(subscriber)
     case Some(Failure(t)) ⇒
-      subscriber.onError(t)
+      tryOnError(subscriber, t)
       removeSubscriber(subscriber)
     case None ⇒ // not completed yet
   }
 
   def registerSubscriber(subscriber: Subscriber[Any]): Unit = {
-    if (subscribers.contains(subscriber))
-      subscriber.onError(new IllegalStateException(s"${getClass.getSimpleName} [$self, sub: $subscriber] ${ReactiveStreamsCompliance.CanNotSubscribeTheSameSubscriberMultipleTimes}"))
+    if (subscribers.contains(subscriber)) // FIXME this is not legal AFAICT, needs to check identity, not equality
+      rejectDuplicateSubscriber(subscriber)
     else {
       val subscription = new FutureSubscription(self)
       subscribers = subscribers.updated(subscriber, subscription)
       subscriptions = subscriptions.updated(subscription, subscriber)
-      subscriber.onSubscribe(subscription)
+      tryOnSubscribe(subscriber, subscription)
     }
   }
 
@@ -127,7 +137,7 @@ private[akka] class FuturePublisher(future: Future[Any], settings: MaterializerS
     }
   }
 
-  override def postStop(): Unit =
+  override def postStop(): Unit = // FIXME if something blows up, are the subscribers onErrored?
     if (exposedPublisher ne null)
       exposedPublisher.shutdown(shutdownReason)
 

akka-stream/src/main/scala/akka/stream/impl/IteratorPublisher.scala

@@ -66,11 +66,15 @@ private[akka] class IteratorPublisher(iterator: Iterator[Any], settings: Materia
 
   def active: Receive = {
     case RequestMore(_, elements) ⇒
+      if (elements < 1)
+        stop(Errored(numberOfElementsInRequestMustBePositiveException))
+      else {
         downstreamDemand += elements
         if (downstreamDemand < 0) // Long has overflown, reactive-streams specification rule 3.17
-        stop(Errored(new IllegalStateException(TotalPendingDemandMustNotExceedLongMaxValue)))
+          stop(Errored(totalPendingDemandMustNotExceedLongMaxValueException))
         else
           push()
+      }
     case PushMore ⇒
       push()
     case _: Cancel ⇒

akka-stream/src/main/scala/akka/stream/impl/Messages.scala

@@ -17,7 +17,7 @@ private[akka] case class RequestMore(subscription: ActorSubscription[_], demand:
 /**
  * INTERNAL API
  */
-private[akka] case class Cancel(subscriptions: ActorSubscription[_])
+private[akka] case class Cancel(subscription: ActorSubscription[_])
 /**
  * INTERNAL API
  */

akka-stream/src/main/scala/akka/stream/impl/ReactiveStreamsCompliance.scala

@@ -20,11 +20,26 @@ private[stream] object ReactiveStreamsCompliance {
   final val TotalPendingDemandMustNotExceedLongMaxValue =
     "Total pending demand MUST NOT be > `java.lang.Long.MAX_VALUE` (see reactive-streams specification, rule 3.17)"
 
-  final def validateRequest(n: Long): Unit =
-    if (n < 1) throw new IllegalArgumentException(NumberOfElementsInRequestMustBePositiveMsg) with SpecViolation
+  final def totalPendingDemandMustNotExceedLongMaxValueException: Throwable =
+    new IllegalStateException(TotalPendingDemandMustNotExceedLongMaxValue)
 
-  final def rejectAdditionalSubscriber[T](subsriber: Subscriber[T], rejector: Publisher[T]): Unit =
-    tryOnError(subsriber, new IllegalStateException(s"$rejector $SupportsOnlyASingleSubscriber"))
+  final def numberOfElementsInRequestMustBePositiveException: Throwable =
+    new IllegalArgumentException(NumberOfElementsInRequestMustBePositiveMsg)
+
+  final def canNotSubscribeTheSameSubscriberMultipleTimesException: Throwable =
+    new IllegalStateException(CanNotSubscribeTheSameSubscriberMultipleTimes)
+
+  final def rejectDuplicateSubscriber[T](subscriber: Subscriber[T]): Unit =
+    tryOnError(subscriber, canNotSubscribeTheSameSubscriberMultipleTimesException)
+
+  final def rejectAdditionalSubscriber[T](subscriber: Subscriber[T], rejector: Publisher[T]): Unit =
+    tryOnError(subscriber, new IllegalStateException(s"$rejector $SupportsOnlyASingleSubscriber"))
+
+  final def rejectDueToOverflow[T](subscriber: Subscriber[T]): Unit =
+    tryOnError(subscriber, totalPendingDemandMustNotExceedLongMaxValueException)
+
+  final def rejectDueToNonPositiveDemand[T](subscriber: Subscriber[T]): Unit =
+    tryOnError(subscriber, numberOfElementsInRequestMustBePositiveException)
 
   sealed trait SpecViolation {
     self: Throwable ⇒

akka-stream/src/main/scala/akka/stream/impl/StreamOfStreamProcessors.scala

@@ -24,9 +24,7 @@ private[akka] object MultiStreamOutputProcessor {
   case class SubstreamSubscriptionTimeout(substream: SubstreamKey)
 
   class SubstreamSubscription(val parent: ActorRef, val substreamKey: SubstreamKey) extends Subscription {
-    override def request(elements: Long): Unit =
-      if (elements <= 0) throw new IllegalArgumentException(ReactiveStreamsCompliance.NumberOfElementsInRequestMustBePositiveMsg)
-      else parent ! SubstreamRequestMore(substreamKey, elements)
+    override def request(elements: Long): Unit = parent ! SubstreamRequestMore(substreamKey, elements)
     override def cancel(): Unit = parent ! SubstreamCancel(substreamKey)
     override def toString = "SubstreamSubscription" + System.identityHashCode(this)
   }

akka-stream/src/main/scala/akka/stream/impl/SubscriberManagement.scala

@@ -41,17 +41,6 @@ private[akka] trait SubscriptionWithCursor[T] extends Subscription with Resizabl
 
   def dispatch(element: T): Unit = subscriber.onNext(element)
 
-  /** Increases the `requested` counter, additionally providing overflow protection */
-  def moreRequested(demand: Long): Long = {
-    val sum = totalDemand + demand
-    val noOverflow = sum > 0
-
-    if (noOverflow) totalDemand = sum
-    else subscriber.onError(new IllegalStateException(s"Total pending demand ($totalDemand + $demand) would overflow `Long`, for Subscriber $subscriber! ${ReactiveStreamsCompliance.TotalPendingDemandMustNotExceedLongMaxValue}"))
-
-    sum
-  }
-
   var active = true
 
   /** Do not increment directly, use `moreRequested(Long)` instead (it provides overflow protection)! */
@@ -112,20 +101,32 @@ private[akka] trait SubscriberManagement[T] extends ResizableMultiReaderRingBuff
    */
   protected def moreRequested(subscription: S, elements: Long): Unit =
     if (subscription.active) {
+      import ReactiveStreamsCompliance._
+      // check for illegal demand See 3.9
+      if (elements < 1) {
+        try tryOnError(subscription.subscriber, numberOfElementsInRequestMustBePositiveException)
+        finally unregisterSubscriptionInternal(subscription)
+      } else {
+        endOfStream match {
+          case eos @ (NotReached | Completed) ⇒
+            val demand = subscription.totalDemand + elements
+            //Check for overflow
+            if (demand < 1) {
+              try tryOnError(subscription.subscriber, totalPendingDemandMustNotExceedLongMaxValueException)
+              finally unregisterSubscriptionInternal(subscription)
+            } else {
+              subscription.totalDemand = demand
               // returns Long.MinValue if the subscription is to be terminated
               @tailrec def dispatchFromBufferAndReturnRemainingRequested(requested: Long, eos: EndOfStream): Long =
                 if (requested == 0) {
                   // if we are at end-of-stream and have nothing more to read we complete now rather than after the next `requestMore`
                   if ((eos ne NotReached) && buffer.count(subscription) == 0) Long.MinValue else 0
                 } else if (buffer.count(subscription) > 0) {
-          subscription.dispatch(buffer.read(subscription))
+                  subscription.dispatch(buffer.read(subscription)) // FIXME this does not gracefully handle the case if onNext throws
                   dispatchFromBufferAndReturnRemainingRequested(requested - 1, eos)
                 } else if (eos ne NotReached) Long.MinValue
                 else requested
 
-      endOfStream match {
-        case eos @ (NotReached | Completed) ⇒
-          val demand = subscription.moreRequested(elements)
               dispatchFromBufferAndReturnRemainingRequested(demand, eos) match {
                 case Long.MinValue ⇒
                   eos(subscription.subscriber)
@@ -134,9 +135,11 @@ private[akka] trait SubscriberManagement[T] extends ResizableMultiReaderRingBuff
                   subscription.totalDemand = x
                   requestFromUpstreamIfRequired()
               }
+            }
           case ErrorCompleted(_) ⇒ // ignore, the Subscriber might not have seen our error event yet
         }
       }
+    }
 
   private[this] final def requestFromUpstreamIfRequired(): Unit = {
     @tailrec def maxRequested(remaining: Subscriptions, result: Long = 0): Long =
@@ -212,20 +215,17 @@ private[akka] trait SubscriberManagement[T] extends ResizableMultiReaderRingBuff
    * Register a new subscriber.
    */
   protected def registerSubscriber(subscriber: Subscriber[_ >: T]): Unit = endOfStream match {
-    case NotReached if subscriptions.exists(_.subscriber eq subscriber) ⇒
-      subscriber.onError(new IllegalStateException(s"${getClass.getSimpleName} [${this}, sub: $subscriber] ${ReactiveStreamsCompliance.CanNotSubscribeTheSameSubscriberMultipleTimes}"))
-    case NotReached ⇒
+    case NotReached if subscriptions.exists(_.subscriber eq subscriber) ⇒ ReactiveStreamsCompliance.rejectDuplicateSubscriber(subscriber)
+    case NotReached ⇒ addSubscription(subscriber)
+    case Completed if buffer.nonEmpty ⇒ addSubscription(subscriber)
+    case eos ⇒ eos(subscriber)
+  }
+
+  protected def addSubscription(subscriber: Subscriber[_ >: T]): Unit = {
     val newSubscription = createSubscription(subscriber)
     subscriptions ::= newSubscription
     buffer.initCursor(newSubscription)
-      subscriber.onSubscribe(newSubscription)
-    case Completed if buffer.nonEmpty ⇒
-      val newSubscription = createSubscription(subscriber)
-      subscriptions ::= newSubscription
-      buffer.initCursor(newSubscription)
-      subscriber.onSubscribe(newSubscription)
-    case eos ⇒
-      eos(subscriber)
+    ReactiveStreamsCompliance.tryOnSubscribe(subscriber, newSubscription) // FIXME what if this throws?
   }
 
   /**

akka-stream/src/main/scala/akka/stream/impl/SynchronousIterablePublisher.scala

@@ -28,49 +28,66 @@ private[akka] object SynchronousIterablePublisher {
     var pendingDemand = 0L
     var pushing = false
 
+    import ReactiveStreamsCompliance._
+
     def init(): Unit = try {
-      if (!iterator.hasNext) {
+      if (!iterator.hasNext) { // Let's be prudent and issue onComplete immediately
         cancel()
-        subscriber.onSubscribe(this)
-        subscriber.onComplete()
+        tryOnSubscribe(subscriber, this)
+        tryOnComplete(subscriber)
       } else {
-        subscriber.onSubscribe(this)
+        tryOnSubscribe(subscriber, this)
       }
     } catch {
+      case sv: SpecViolation ⇒
+        cancel()
+        throw sv.violation // I think it is prudent to "escalate" the spec violation
       case NonFatal(e) ⇒
         cancel()
-        subscriber.onError(e)
+        tryOnError(subscriber, e)
     }
 
-    override def cancel(): Unit =
-      done = true
+    override def cancel(): Unit = done = true
 
     override def request(elements: Long): Unit = {
-      if (elements < 1) throw new IllegalArgumentException(ReactiveStreamsCompliance.NumberOfElementsInRequestMustBePositiveMsg)
-      @tailrec def pushNext(): Unit = {
-        if (!done)
-          if (iterator.isEmpty) {
+      if (done) () // According to Reactive Streams Spec 3.6, `request` on a cancelled `Subscription` must be a NoOp
+      else if (elements < 1) { // According to Reactive Streams Spec 3.9, with non-positive demand must yield onError
         cancel()
-            subscriber.onComplete() // FIXME this is technically incorrect since if onComplete throws an Exception, we'll call onError (illegal)
-          } else if (pendingDemand > 0) {
-            pendingDemand -= 1
-            subscriber.onNext(iterator.next())
-            pushNext()
-          }
-      }
-
-      if (pushing)
-        pendingDemand += elements // reentrant call to requestMore from onNext // FIXME This severely lacks overflow checks
-      else {
+        rejectDueToNonPositiveDemand(subscriber)
+      } else {
+        pendingDemand += elements
+        if (pendingDemand < 1) { // According to Reactive Streams Spec 3:17, if we overflow 2^63-1, we need to yield onError
+          cancel()
+          rejectDueToOverflow(subscriber)
+        } else if (!pushing) {
+          // According to Reactive Streams Spec 3:3, we must prevent unbounded recursion
           try {
             pushing = true
             pendingDemand = elements
+
+            @tailrec def pushNext(): Unit =
+              if (done) ()
+              else if (iterator.isEmpty) {
+                cancel()
+                tryOnComplete(subscriber)
+              } else if (pendingDemand > 0) {
+                pendingDemand -= 1
+                tryOnNext(subscriber, iterator.next())
+                pushNext()
+              }
+
             pushNext()
           } catch {
+            case sv: SpecViolation ⇒
+              cancel()
+              throw sv.violation // I think it is prudent to "escalate" the spec violation
             case NonFatal(e) ⇒
               cancel()
-            subscriber.onError(e)
-        } finally { pushing = false }
+              tryOnError(subscriber, e)
+          } finally {
+            pushing = false
+          }
+        }
       }
     }
   }
@@ -96,7 +113,8 @@ private[akka] final class SynchronousIterablePublisher[T](
 
   import SynchronousIterablePublisher.IteratorSubscription
 
-  override def subscribe(subscriber: Subscriber[_ >: T]): Unit = IteratorSubscription(subscriber, iterable.iterator) //FIXME what if .iterator throws?
+  override def subscribe(subscriber: Subscriber[_ >: T]): Unit =
+    IteratorSubscription(subscriber, try iterable.iterator catch { case NonFatal(t) ⇒ Iterator.continually(throw t) })
 
   override def toString: String = name
 }

akka-stream/src/main/scala/akka/stream/impl/TickPublisher.scala

@@ -29,9 +29,7 @@ private[akka] object TickPublisher {
   class TickPublisherSubscription(ref: ActorRef) extends Subscription {
     import akka.stream.impl.TickPublisher.TickPublisherSubscription._
     def cancel(): Unit = ref ! Cancel
-    def request(elements: Long): Unit =
-      if (elements <= 0) throw new IllegalArgumentException(ReactiveStreamsCompliance.NumberOfElementsInRequestMustBePositiveMsg)
-      else ref ! RequestMore(elements)
+    def request(elements: Long): Unit = ref ! RequestMore(elements)
     override def toString = "TickPublisherSubscription"
   }
 
@@ -49,6 +47,7 @@ private[akka] class TickPublisher(initialDelay: FiniteDuration, interval: Finite
                                   settings: MaterializerSettings, cancelled: AtomicBoolean) extends Actor with SoftShutdown {
   import akka.stream.impl.TickPublisher.TickPublisherSubscription._
   import akka.stream.impl.TickPublisher._
+  import ReactiveStreamsCompliance._
 
   var exposedPublisher: ActorPublisher[Any] = _
   private var subscriber: Subscriber[_ >: Any] = null
@@ -73,31 +72,36 @@ private[akka] class TickPublisher(initialDelay: FiniteDuration, interval: Finite
       context.become(active)
   }
 
+  def handleError(error: Throwable): Unit = {
+    try {
+      if (!error.isInstanceOf[SpecViolation])
+        tryOnError(subscriber, error)
+    } finally {
+      subscriber = null
+      exposedPublisher.shutdown(Some(error)) // FIXME should this not be SupportsOnlyASingleSubscriber?
+      context.stop(self)
+    }
+  }
+
   def active: Receive = {
     case Tick ⇒
       try {
-        val tickElement = tick()
+        val tickElement = tick() // FIXME should we call this even if we shouldn't send it?
         if (demand > 0) {
           demand -= 1
-          subscriber.onNext(tickElement)
+          tryOnNext(subscriber, tickElement)
         }
       } catch {
-        case NonFatal(e) ⇒
-          if (subscriber ne null) {
-            subscriber.onError(e)
-            subscriber = null
-          }
-          exposedPublisher.shutdown(Some(e))
-          context.stop(self)
+        case NonFatal(e) ⇒ handleError(e)
       }
 
     case RequestMore(elements) ⇒
+      if (elements < 1) {
+        handleError(numberOfElementsInRequestMustBePositiveException)
+      } else {
         demand += elements
-      if (demand < 0) {
-        // Long has overflown, reactive-streams specification rule 3.17
-        exposedPublisher.shutdown(Some(
-          new IllegalStateException(ReactiveStreamsCompliance.TotalPendingDemandMustNotExceedLongMaxValue)))
-        context.stop(self)
+        if (demand < 0) // Long has overflown, reactive-streams specification rule 3.17
+          handleError(totalPendingDemandMustNotExceedLongMaxValueException)
       }
 
     case Cancel ⇒
@@ -106,25 +110,23 @@ private[akka] class TickPublisher(initialDelay: FiniteDuration, interval: Finite
 
     case SubscribePending ⇒
       exposedPublisher.takePendingSubscribers() foreach registerSubscriber
-
   }
 
-  def registerSubscriber(s: Subscriber[_ >: Any]): Unit = {
-    if (subscriber ne null) s.onError(new IllegalStateException(s"${getClass.getSimpleName} [$self, sub: $subscriber] ${ReactiveStreamsCompliance.CanNotSubscribeTheSameSubscriberMultipleTimes}"))
-    else {
+  def registerSubscriber(s: Subscriber[_ >: Any]): Unit = subscriber match {
+    case null ⇒
       val subscription = new TickPublisherSubscription(self)
       subscriber = s
-      subscriber.onSubscribe(subscription)
-    }
+      tryOnSubscribe(s, subscription)
+    case _ ⇒
+      rejectAdditionalSubscriber(s, exposedPublisher)
   }
 
   override def postStop(): Unit = {
     tickTask.foreach(_.cancel)
     cancelled.set(true)
-    if (subscriber ne null) subscriber.onComplete()
+    if (subscriber ne null) tryOnComplete(subscriber)
     if (exposedPublisher ne null)
       exposedPublisher.shutdown(ActorPublisher.NormalShutdownReason)
   }
-
 }
 

akka-stream/src/main/scala/akka/stream/impl/fusing/ActorInterpreter.scala

@@ -220,18 +220,20 @@ private[akka] class ActorOutputBoundary(val actor: ActorRef) extends BoundarySta
     case SubscribePending ⇒
       subscribePending(exposedPublisher.takePendingSubscribers())
     case RequestMore(subscription, elements) ⇒
-
-      // TODO centralize overflow protection
-      downstreamDemand += elements
-      if (downstreamDemand < 0) {
-        // Long has overflown
-        val demandOverflowException = new IllegalStateException(ReactiveStreamsCompliance.TotalPendingDemandMustNotExceedLongMaxValue)
+      if (elements < 1) {
         enter().finish()
-        fail(demandOverflowException)
+        fail(ReactiveStreamsCompliance.numberOfElementsInRequestMustBePositiveException)
+      } else {
+        downstreamDemand += elements
+        // Long has overflown
+        if (downstreamDemand < 0) {
+          enter().finish()
+          fail(ReactiveStreamsCompliance.totalPendingDemandMustNotExceedLongMaxValueException)
         } else if (upstreamWaiting) {
           upstreamWaiting = false
           enter().pull()
         }
+      }
 
     case Cancel(subscription) ⇒
       downstreamCompleted = true