serialize Scala 2.12 functions for when used in remote deployment, #22041

akka-actor-tests/src/test/scala/akka/serialization/SerializeSpec.scala

@@ -331,6 +331,15 @@ class ReferenceSerializationSpec extends AkkaSpec(SerializationTests.mostlyRefer
       intercept[NotSerializableException] { ser.serializerFor(classOf[Object]) }
     }
 
+    "serialize function with JavaSerializer" in {
+      val f = (i: Int) ⇒ i + 1
+      val serializer = ser.serializerFor(f.getClass)
+      serializer.getClass should ===(classOf[JavaSerializer])
+      val bytes = ser.serialize(f).get
+      val f2 = ser.deserialize(bytes, serializer.identifier, "").get.asInstanceOf[Function1[Int, Int]]
+      f2(3) should ===(4)
+    }
+
   }
 }
 
@@ -424,6 +433,7 @@ class SerializationCompatibilitySpec extends AkkaSpec(SerializationTests.mostlyR
           "626c653b4c00056368696c647400154c616b6b612f6163746f722f4163746f725265663b78700000" +
           "00007070")
     }
+
   }
 }
 

akka-remote/src/main/scala/akka/remote/serialization/DaemonMsgCreateSerializer.scala

@@ -13,6 +13,7 @@ import akka.remote.WireFormats.{ DaemonMsgCreateData, DeployData, PropsData }
 import akka.routing.{ NoRouter, RouterConfig }
 import scala.reflect.ClassTag
 import util.{ Failure, Success }
+import java.io.Serializable
 
 /**
  * Serializes Akka's internal DaemonMsgCreate using protobuf
@@ -31,6 +32,8 @@ private[akka] class DaemonMsgCreateSerializer(val system: ExtendedActorSystem) e
   @deprecated("Use constructor with ExtendedActorSystem", "2.4")
   def this() = this(null)
 
+  private val scala212OrLater = !scala.util.Properties.versionNumberString.startsWith("2.11")
+
   // TODO remove this when deprecated this() is removed
   override val identifier: Int =
     if (system eq null) 3
@@ -61,7 +64,22 @@ private[akka] class DaemonMsgCreateSerializer(val system: ExtendedActorSystem) e
           .setClazz(props.clazz.getName)
           .setDeploy(deployProto(props.deploy))
         props.args map serialize foreach builder.addArgs
-        props.args map (a ⇒ if (a == null) "null" else a.getClass.getName) foreach builder.addClasses
+        props.args.map { a ⇒
+          val argClassName =
+            if (a == null) "null"
+            else {
+              val className = a.getClass.getName
+              if (scala212OrLater && a.getClass.isInstanceOf[Serializable] && a.getClass.isSynthetic &&
+                className.contains("$Lambda$")) {
+                // The serialization of the parameters is based on passing class name instead of
+                // serializerId and manifest as we usually do. With Scala 2.12 the functions are generated as
+                // lambdas and we can't use that load class from that name when deserializing.
+                classOf[Serializable].getName
+              } else
+                className
+            }
+          builder.addClasses(argClassName)
+        }
         builder.build
       }
 

akka-remote/src/test/scala/akka/remote/serialization/DaemonMsgCreateSerializerSpec.scala

@@ -11,7 +11,6 @@ import akka.testkit.AkkaSpec
 import akka.actor.{ Actor, Address, Props, Deploy, OneForOneStrategy, SupervisorStrategy }
 import akka.remote.{ DaemonMsgCreate, RemoteScope }
 import akka.routing.{ RoundRobinPool, FromConfig }
-import akka.util.IgnoreForScala212
 import scala.concurrent.duration._
 
 object DaemonMsgCreateSerializerSpec {
@@ -22,6 +21,10 @@ object DaemonMsgCreateSerializerSpec {
   class MyActorWithParam(ignore: String) extends Actor {
     def receive = Actor.emptyBehavior
   }
+
+  class MyActorWithFunParam(fun: Function1[Int, Int]) extends Actor {
+    def receive = Actor.emptyBehavior
+  }
 }
 
 class DaemonMsgCreateSerializerSpec extends AkkaSpec {
@@ -56,7 +59,7 @@ class DaemonMsgCreateSerializerSpec extends AkkaSpec {
       }
     }
 
-    "serialize and de-serialize DaemonMsgCreate with function creator" taggedAs IgnoreForScala212 in {
+    "serialize and de-serialize DaemonMsgCreate with function creator" in {
       verifySerialization {
         DaemonMsgCreate(
           props = Props(new MyActor),
@@ -66,6 +69,16 @@ class DaemonMsgCreateSerializerSpec extends AkkaSpec {
       }
     }
 
+    "serialize and de-serialize DaemonMsgCreate with FromClassCreator, with function parameters for Props" in {
+      verifySerialization {
+        DaemonMsgCreate(
+          props = Props(classOf[MyActorWithFunParam], (i: Int) ⇒ i + 1),
+          deploy = Deploy(),
+          path = "foo",
+          supervisor = supervisor)
+      }
+    }
+
     "serialize and de-serialize DaemonMsgCreate with Deploy and RouterConfig" in {
       verifySerialization {
         // Duration.Inf doesn't equal Duration.Inf, so we use another for test
@@ -103,6 +116,7 @@ class DaemonMsgCreateSerializerSpec extends AkkaSpec {
       got.props.args zip expected.props.args foreach {
         case (g, e) ⇒
           if (e.isInstanceOf[Function0[_]]) ()
+          else if (e.isInstanceOf[Function1[_, _]]) ()
           else g should ===(e)
       }
       got.props.deploy should ===(expected.props.deploy)

project/Dependencies.scala

@@ -17,8 +17,8 @@ object Dependencies {
   val sslConfigVersion = "0.2.1"
 
   val Versions = Seq(
-    crossScalaVersions := Seq("2.11.8"), // "2.12.0"
-    scalaVersion := crossScalaVersions.value.head,
+    crossScalaVersions := Seq("2.11.8", "2.12.1"),
+    scalaVersion := System.getProperty("akka.build.scalaVersion", crossScalaVersions.value.head),
     scalaStmVersion := sys.props.get("akka.build.scalaStmVersion").getOrElse("0.8"),
     scalaCheckVersion := sys.props.get("akka.build.scalaCheckVersion").getOrElse(
       if (scalaVersion.value.startsWith("2.12")) "1.13.4" // does not work for 2.11