From 8c058678ca5fd4bf30172772b3e1db27860dac7a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johan=20Andr=C3=A9n?= <johan@markatta.com>
Date: Fri, 21 Sep 2018 15:24:01 +0200
Subject: [PATCH] Disallow nested mixed widen usages, #25604

---
 .../scala/akka/actor/typed/WidenSpec.scala    | 49 ++++++++++++++++---
 .../typed/internal/InterceptorImpl.scala      |  9 +++-
 2 files changed, 50 insertions(+), 8 deletions(-)

diff --git a/akka-actor-typed-tests/src/test/scala/akka/actor/typed/WidenSpec.scala b/akka-actor-typed-tests/src/test/scala/akka/actor/typed/WidenSpec.scala
index a108497478..439dc5c847 100644
--- a/akka-actor-typed-tests/src/test/scala/akka/actor/typed/WidenSpec.scala
+++ b/akka-actor-typed-tests/src/test/scala/akka/actor/typed/WidenSpec.scala
@@ -6,12 +6,22 @@ package akka.actor.typed
 
 import java.util.concurrent.atomic.AtomicInteger
 
+import akka.actor.ActorInitializationException
 import akka.actor.testkit.typed.scaladsl.ScalaTestWithActorTestKit
 import akka.actor.testkit.typed.scaladsl.TestProbe
 import akka.actor.typed.scaladsl.Behaviors
+import akka.actor.typed.scaladsl.adapter._
+import akka.testkit.EventFilter
 import org.scalatest.WordSpecLike
 
-class WidenSpec extends ScalaTestWithActorTestKit with WordSpecLike {
+import scala.concurrent.duration._
+
+class WidenSpec extends ScalaTestWithActorTestKit(
+  """
+    akka.loggers = [akka.testkit.TestEventListener]
+    """) with WordSpecLike {
+
+  implicit val untypedSystem = system.toUntyped
 
   def intToString(probe: ActorRef[String]): Behavior[Int] = {
     Behaviors.receiveMessage[String] { msg ⇒
@@ -36,11 +46,14 @@ class WidenSpec extends ScalaTestWithActorTestKit with WordSpecLike {
       val probe = TestProbe[String]()
       val ref = spawn(intToString(probe.ref))
 
-      ref ! 42
-      ref ! 13
-      ref ! 43
-      probe.expectMessage("42")
-      probe.expectMessage("43")
+      // TestEventListener logs unhandled as warnings, silence that
+      EventFilter.warning(occurrences = 1).intercept {
+        ref ! 42
+        ref ! 13
+        ref ! 43
+        probe.expectMessage("42")
+        probe.expectMessage("43")
+      }
     }
 
     "not build up when the same widen is used many times (initially)" in {
@@ -105,6 +118,30 @@ class WidenSpec extends ScalaTestWithActorTestKit with WordSpecLike {
       transformCount.get should ===(2)
 
     }
+
+    "not allow mixing different widens in the same behavior stack" in {
+      val probe = TestProbe[String]()
+
+      def widen(behavior: Behavior[String]): Behavior[String] =
+        behavior.widen[String] {
+          case s ⇒ s.toLowerCase
+        }
+
+      EventFilter[ActorInitializationException](occurrences = 1).intercept {
+        val ref = spawn(
+          widen(
+            widen(
+              Behaviors.receiveMessage[String] { msg ⇒
+                Behaviors.same
+              }
+            )
+          )
+        )
+
+        probe.expectTerminated(ref, 3.seconds)
+      }
+
+    }
   }
 
 }
diff --git a/akka-actor-typed/src/main/scala/akka/actor/typed/internal/InterceptorImpl.scala b/akka-actor-typed/src/main/scala/akka/actor/typed/internal/InterceptorImpl.scala
index 6e21664a7f..0feecfec3f 100644
--- a/akka-actor-typed/src/main/scala/akka/actor/typed/internal/InterceptorImpl.scala
+++ b/akka-actor-typed/src/main/scala/akka/actor/typed/internal/InterceptorImpl.scala
@@ -138,9 +138,14 @@ private[akka] final case class WidenedInterceptor[O, I](matcher: PartialFunction
   import BehaviorInterceptor._
 
   override def isSame(other: BehaviorInterceptor[Any, Any]): Boolean = other match {
-    // can only be elimintated if it is the same partial function
+    // If they use the same pf instance we can allow it, to have one way to workaround defining
+    // "recursive" narrowed behaviors.
     case WidenedInterceptor(`matcher`) ⇒ true
-    case _                             ⇒ false
+    case WidenedInterceptor(otherMatcher) ⇒
+      // there is no safe way to allow this
+      throw new IllegalStateException("Widen can only be used one time in the same behavior stack. " +
+        s"One defined in ${LineNumbers(matcher)}, and another in ${LineNumbers(otherMatcher)}")
+    case _ ⇒ false
   }
 
   def aroundReceive(ctx: ActorContext[O], msg: O, target: ReceiveTarget[I]): Behavior[I] = {