=act #3733 Re-receive unstashed Terminated messages

akka-actor-tests/src/test/scala/akka/actor/ActorWithStashSpec.scala

@@ -66,6 +66,27 @@ object ActorWithStashSpec {
     }
   }
 
+  class WatchedActor extends Actor {
+    def receive = Actor.emptyBehavior
+  }
+
+  class TerminatedMessageStashingActor(probe: ActorRef) extends Actor with Stash {
+    val watched = context.watch(context.actorOf(Props[WatchedActor]))
+    var stashed = false
+
+    context.stop(watched)
+
+    def receive = {
+      case Terminated(`watched`) ⇒
+        if (!stashed) {
+          stash()
+          stashed = true
+          unstashAll()
+        }
+        probe ! "terminated"
+    }
+  }
+
   object state {
     @volatile
     var s: String = ""
@@ -156,6 +177,12 @@ class ActorWithStashSpec extends AkkaSpec(ActorWithStashSpec.testConf) with Defa
       Await.ready(restartLatch, 10 seconds)
       Await.ready(hasMsgLatch, 10 seconds)
     }
+
+    "re-receive unstashed Terminated messages" in {
+      system.actorOf(Props(classOf[TerminatedMessageStashingActor], testActor))
+      expectMsg("terminated")
+      expectMsg("terminated")
+    }
   }
 
   "An ActWithStash" must {

akka-actor/src/main/scala/akka/actor/Stash.scala

@@ -119,6 +119,8 @@ private[akka] trait StashSupport {
    */
   private var theStash = Vector.empty[Envelope]
 
+  private def actorCell = context.asInstanceOf[ActorCell]
+
   /* The capacity of the stash. Configured in the actor's mailbox or dispatcher config.
    */
   private val capacity: Int = {
@@ -137,7 +139,7 @@ private[akka] trait StashSupport {
    * `mailbox.queue` is the underlying `Deque`.
    */
   private[akka] val mailbox: DequeBasedMessageQueueSemantics = {
-    context.asInstanceOf[ActorCell].mailbox.messageQueue match {
+    actorCell.mailbox.messageQueue match {
       case queue: DequeBasedMessageQueueSemantics ⇒ queue
       case other ⇒ throw ActorInitializationException(self, s"DequeBasedMailbox required, got: ${other.getClass.getName}\n" +
         """An (unbounded) deque-based mailbox can be configured as follows:
@@ -156,7 +158,7 @@ private[akka] trait StashSupport {
    *  @throws IllegalStateException  if the same message is stashed more than once
    */
   def stash(): Unit = {
-    val currMsg = context.asInstanceOf[ActorCell].currentMessage
+    val currMsg = actorCell.currentMessage
     if (theStash.nonEmpty && (currMsg eq theStash.last))
       throw new IllegalStateException("Can't stash the same message " + currMsg + " more than once")
     if (capacity <= 0 || theStash.size < capacity) theStash :+= currMsg
@@ -182,7 +184,7 @@ private[akka] trait StashSupport {
    *  if the `unstash()` call successfully returns or throws an exception.
    */
   private[akka] def unstash(): Unit = if (theStash.nonEmpty) try {
-    mailbox.enqueueFirst(self, theStash.head)
+    enqueueFirst(theStash.head)
   } finally {
     theStash = theStash.tail
   }
@@ -216,7 +218,7 @@ private[akka] trait StashSupport {
   private[akka] def unstashAll(filterPredicate: Any ⇒ Boolean): Unit = {
     try {
       val i = theStash.reverseIterator.filter(envelope ⇒ filterPredicate(envelope.message))
-      while (i.hasNext) mailbox.enqueueFirst(self, i.next())
+      while (i.hasNext) enqueueFirst(i.next())
     } finally {
       theStash = Vector.empty[Envelope]
     }
@@ -232,6 +234,19 @@ private[akka] trait StashSupport {
     theStash = Vector.empty[Envelope]
     stashed
   }
+
+  /**
+   * Enqueues `envelope` at the first position in the mailbox. If the message contained in
+   * the envelope is a `Terminated` message, it will be ensured that it can be re-received
+   * by the actor.
+   */
+  private def enqueueFirst(envelope: Envelope): Unit = {
+    mailbox.enqueueFirst(self, envelope)
+    envelope.message match {
+      case Terminated(ref) ⇒ actorCell.terminatedQueuedFor(ref)
+      case _               ⇒
+    }
+  }
 }
 
 /**

akka-actor/src/main/scala/akka/actor/dungeon/DeathWatch.scala

@@ -57,11 +57,14 @@ private[akka] trait DeathWatch { this: ActorCell ⇒
       }
       if (!isTerminating) {
         self.tell(Terminated(actor)(existenceConfirmed, addressTerminated), actor)
-        terminatedQueued += actor
+        terminatedQueuedFor(actor)
       }
     }
   }
 
+  private[akka] def terminatedQueuedFor(subject: ActorRef): Unit =
+    terminatedQueued += subject
+
   // TODO this should be removed and be replaced with `watching.contains(subject)`
   //   when all actor references have uid, i.e. actorFor is removed
   private def watchingContains(subject: ActorRef): Boolean =