Fix stack overflow for dead letters message adapter, #31241 (#31249)

akka-actor-typed-tests/src/test/scala/akka/actor/typed/eventstream/EventStreamSpec.scala

@@ -4,12 +4,17 @@
 
 package akka.actor.typed.eventstream
 
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
+
 import scala.concurrent.duration._
 
 import org.scalatest.wordspec.AnyWordSpecLike
 
+import akka.actor.DeadLetter
 import akka.actor.testkit.typed.scaladsl.{ ScalaTestWithActorTestKit, TestProbe }
 import akka.actor.testkit.typed.scaladsl.LogCapturing
+import akka.actor.typed.scaladsl.Behaviors
 
 class EventStreamSpec extends ScalaTestWithActorTestKit with AnyWordSpecLike with LogCapturing {
 
@@ -43,6 +48,56 @@ class EventStreamSpec extends ScalaTestWithActorTestKit with AnyWordSpecLike wit
       testKit.system.eventStream ! Publish(EventObj)
       eventObjListener.expectNoMessage(ShortWait)
     }
+
+    "be subscribed by message adapter for DeadLetter" in {
+      val probe = createTestProbe[String]()
+      val ref = testKit.spawn(Behaviors.setup[String] { context =>
+        val adapter = context.messageAdapter[DeadLetter](d => d.message.toString)
+        context.system.eventStream ! Subscribe(adapter)
+
+        Behaviors.receiveMessage { msg =>
+          probe.ref ! msg
+          Behaviors.same
+        }
+      })
+
+      ref ! "init"
+      probe.expectMessage("init")
+      probe.expectNoMessage(100.millis) // might still be a risk that the eventStream ! Subscribe hasn't arrived
+
+      testKit.system.deadLetters ! "msg1"
+      testKit.system.deadLetters ! "msg2"
+      testKit.system.deadLetters ! "msg3"
+
+      probe.expectMessage("msg1")
+      probe.expectMessage("msg2")
+      probe.expectMessage("msg3")
+    }
+
+    "not cause infinite loop when stopping subscribed by message adapter for DeadLetter" in {
+      val latch = new CountDownLatch(1)
+      val ref = testKit.spawn(Behaviors.setup[String] { context =>
+        val adapter = context.messageAdapter[DeadLetter](d => d.message.toString)
+        context.system.eventStream ! Subscribe(adapter)
+
+        Behaviors.receiveMessage { msg =>
+          latch.await(10, TimeUnit.SECONDS)
+          if (msg == "stop")
+            Behaviors.stopped
+          else
+            Behaviors.same
+        }
+      })
+
+      ref ! "msg1"
+      ref ! "stop"
+      ref ! "msg2"
+      ref ! "msg3"
+      // msg2 and msg3 in mailbox, will be sent to dead letters
+      latch.countDown() // stop
+
+      testKit.createTestProbe().expectTerminated(ref)
+    }
   }
 
   "a system event stream subscriber" must {

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

@@ -240,10 +240,10 @@ private[akka] trait FaultHandling { this: ActorCell =>
     try if (a ne null) a.aroundPostStop()
     catch handleNonFatalOrInterruptedException { e =>
       publish(Error(e, self.path.toString, clazz(a), e.getMessage))
-    } finally try dispatcher.detach(this)
+    } finally try stopFunctionRefs()
+    finally try dispatcher.detach(this)
     finally try parent.sendSystemMessage(
       DeathWatchNotification(self, existenceConfirmed = true, addressTerminated = false))
-    finally try stopFunctionRefs()
     finally try tellWatchersWeDied()
     finally try unwatchWatchedActors(a) // stay here as we expect an emergency stop from handleInvokeFailure
     finally {

akka-actor/src/main/scala/akka/event/EventStream.scala

@@ -8,8 +8,6 @@ import java.util.concurrent.atomic.AtomicReference
 
 import scala.annotation.tailrec
 
-import scala.annotation.nowarn
-
 import akka.actor.{ ActorRef, ActorSystem }
 import akka.event.Logging.simpleName
 import akka.util.Subclassification
@@ -40,8 +38,6 @@ class EventStream(sys: ActorSystem, private val debug: Boolean) extends LoggingB
 
   protected def classify(event: Any): Class[_] = event.getClass
 
-  // TODO consider avoiding the deprecated `isTerminated`?
-  @nowarn("msg=deprecated")
   protected def publish(event: Any, subscriber: ActorRef) = {
     if (sys == null && subscriber.isTerminated) unsubscribe(subscriber)
     else subscriber ! event