Remoting for Akka Typed, #21225

* seems like it will just work when using the adapters, since
  it will simply delegate to the untyped RemoteActorRef
* ActorRefResolver was added for upporting erialization of typed ActorRef
* The ActorRef itself is not serializable with Java serialization,
  and we shouldn't do that

akka-typed/src/main/scala/akka/typed/cluster/ActorRefResolver.scala

@@ -0,0 +1,43 @@
+/**
+ * Copyright (C) 2017 Lightbend Inc. <http://www.lightbend.com>
+ */
+package akka.typed.cluster
+
+import akka.typed.ActorSystem
+import akka.typed.Extension
+import akka.typed.ExtensionId
+import akka.typed.ActorRef
+import akka.actor.ExtendedActorSystem
+
+object ActorRefResolver extends ExtensionId[ActorRefResolver] {
+  def get(system: ActorSystem[_]): ActorRefResolver = apply(system)
+
+  override def createExtension(system: ActorSystem[_]): ActorRefResolver =
+    new ActorRefResolver(system)
+}
+
+/**
+ * Serialization and deserialization of `ActorRef`.
+ */
+class ActorRefResolver(system: ActorSystem[_]) extends Extension {
+  import akka.typed.scaladsl.adapter._
+
+  private val untypedSystem = system.toUntyped.asInstanceOf[ExtendedActorSystem]
+
+  /**
+   * Generate full String representation including the uid for the actor cell
+   * instance as URI fragment, replacing the Address in the RootActor Path
+   * with the local one unless this path’s address includes host and port
+   * information. This representation should be used as serialized
+   * representation.
+   */
+  def toSerializationFormat[T](ref: ActorRef[T]): String =
+    ref.path.toSerializationFormatWithAddress(untypedSystem.provider.getDefaultAddress)
+
+  /**
+   * Deserialize an `ActorRef` in the [[#toSerializationFormat]].
+   */
+  def resolveActorRef[T](serializedActorRef: String): ActorRef[T] =
+    untypedSystem.provider.resolveActorRef(serializedActorRef)
+}
+

build.sbt

@@ -158,7 +158,7 @@ lazy val streamTestsTck = akkaModule("akka-stream-tests-tck")
   .dependsOn(streamTestkit % "test->test", stream)
 
 lazy val typed = akkaModule("akka-typed")
-  .dependsOn(testkit % "compile->compile;test->test")
+  .dependsOn(testkit % "compile->compile;test->test", cluster % "compile->compile;test->test")
 
 lazy val typedTests = akkaModule("akka-typed-tests")
   .dependsOn(typed, typedTestkit % "compile->compile;test->test")