Scala 3 cross compatible akka-actor / akka-testkit / akka-actor-tests (#29956)

* Remove @switch when it doesn't take effect
* Use ActorRef.noSender
* Minor tweaks to SchedulerSpec
* Disambiguate TypedActor for Scala 3
* Bump ScalaTest to a version compatible with Scala 3
* Bump ScalaCheck
* Disambiguate Event in SupervisorHierarchySpec
* Scala 3 compatible EventBusSpec
* Prevent private unused variables to be erased by Scala 3
* Bump mockito
* Explicit actorRef2Scala import
* restore original .scalafix.conf
* Scala 3 compatible tailrec
* Reminder to re add switch annotation in case
* Move to nowarn instead of silencer
* Bump to Scala 2.12.13
* Cross compatible annotations
* fix docs generation
* adapt the build for Scala 3
* fix errors but bus
* remove more SerialVersion from trait
* scalacheck only from scalatest
* cross-compile akka-actor-tests
* restore cross-compilation
* early initializers workaround
* scalacheck switch
* cross compatible FSM.State class
* cross compatible LARS spec
* Change results to pass LineNumberSpec
* fix stackoverflow in AsyncDnsResolverIntegrationSpec
* FSM.State unapply
* fix Scala 2.13 mima
* SerialVersionRemover compiler plugin
* removed unused nowarns

build.sbt

@@ -12,7 +12,6 @@ enablePlugins(
   JavaFormatterPlugin)
 disablePlugins(MimaPlugin)
 
-
 // check format and headers
 TaskKey[Unit]("verifyCodeFmt") := {
   javafmtCheckAll.all(ScopeFilter(inAnyProject)).result.value.toEither.left.foreach { _ =>
@@ -31,12 +30,9 @@ addCommandAlias("applyCodeStyle", "headerCreateAll; javafmtAll; scalafmtAll")
 
 addCommandAlias(
   name = "fixall",
-  value =
-    ";scalafixEnable; scalafixAll; scalafmtAll; test:compile; multi-jvm:compile; reload")
+  value = ";scalafixEnable; scalafixAll; scalafmtAll; test:compile; multi-jvm:compile; reload")
 
-addCommandAlias(
-  name = "sortImports",
-  value = ";scalafixEnable; scalafixAll SortImports; scalafmtAll")
+addCommandAlias(name = "sortImports", value = ";scalafixEnable; scalafixAll SortImports; scalafmtAll")
 
 import akka.AkkaBuild._
 import akka.{ AkkaBuild, Dependencies, OSGi, Protobuf, SigarLoader, VersionGenerator }
@@ -107,7 +103,15 @@ lazy val root = Project(id = "akka", base = file("."))
   .aggregate(aggregatedProjects: _*)
   .enablePlugins(PublishRsyncPlugin)
   .settings(rootSettings: _*)
-  .settings(unidocRootIgnoreProjects := Seq(remoteTests, benchJmh, protobuf, protobufV3, akkaScalaNightly, docs))
+  .settings(
+    unidocRootIgnoreProjects := Seq(
+        remoteTests,
+        benchJmh,
+        protobuf,
+        protobufV3,
+        akkaScalaNightly,
+        docs,
+        serialversionRemoverPlugin))
   .settings(unmanagedSources in (Compile, headerCreate) := (baseDirectory.value / "project").**("*.scala").get)
   .enablePlugins(CopyrightHeaderForBuild)
 
@@ -120,6 +124,7 @@ lazy val actor = akkaModule("akka-actor")
     (scalaSource in Compile).value.getParentFile / s"scala-$ver"
   })
   .settings(VersionGenerator.settings)
+  .settings(serialversionRemoverPluginSettings)
   .enablePlugins(BoilerplatePlugin)
 
 lazy val actorTests = akkaModule("akka-actor-tests")
@@ -571,6 +576,25 @@ lazy val billOfMaterials = Project("akka-bill-of-materials", file("akka-bill-of-
     bomIncludeProjects := userProjects,
     description := s"${description.value} (depending on Scala ${CrossVersion.binaryScalaVersion(scalaVersion.value)})")
 
+lazy val serialversionRemoverPlugin =
+  Project(id = "serialVersionRemoverPlugin", base = file("plugins/serialversion-remover-plugin")).settings(
+    scalaVersion := akka.Dependencies.scala3Version,
+    libraryDependencies += ("org.scala-lang" %% "scala3-compiler" % akka.Dependencies.scala3Version),
+    Compile / doc / sources := Nil,
+    publishArtifact in Compile := false)
+
+lazy val serialversionRemoverPluginSettings = {
+  if (akka.Dependencies.getScalaVersion() == akka.Dependencies.scala3Version) {
+    Seq(
+      autoCompilerPlugins := true,
+      scalacOptions in Compile += (
+          "-Xplugin:" + (Keys.`package` in (serialversionRemoverPlugin, Compile)).value.getAbsolutePath.toString
+        ))
+  } else {
+    Seq()
+  }
+}
+
 def akkaModule(name: String): Project =
   Project(id = name, base = file(name))
     .enablePlugins(ReproducibleBuildsPlugin)