fix: keep Scala 3.8.4 cross builds clean

He-Pin · He-Pin · commit b37b2e9d73dd · 2026-07-05T22:34:12.000+08:00
Motivation:\nPrepare the Pekko Scala 3.8.4 cross-build PRs for future Scala 3 LTS upgrades while preserving Scala 2.13.x and Scala 3.3.x compatibility.

Modification:\nScope Scala 3.3-only compiler options correctly and adjust sources/build settings so Scala 3.8.4 compiles without errors or warnings.

Result:\nThe project cross-builds cleanly across the intended Scala versions, with Scala 3.8.4 kept warning-free where validated locally.
diff --git a/actor-testkit-typed/src/test/scala/org/apache/pekko/actor/testkit/typed/scaladsl/BehaviorTestKitSpec.scala b/actor-testkit-typed/src/test/scala/org/apache/pekko/actor/testkit/typed/scaladsl/BehaviorTestKitSpec.scala
@@ -128,7 +128,11 @@ object BehaviorTestKitSpec {
               replyTo ! Done
               Behaviors.same
             case CreateMessageAdapter(messageClass, f, replyTo) =>
-              val adaptor = context.messageAdapter(f)(ClassTag(messageClass))
+              def createAdapter[U](messageClass: Class[U], f: U => Command): ActorRef[U] = {
+                implicit val classTag: ClassTag[U] = ClassTag(messageClass)
+                context.messageAdapter(f)
+              }
+              val adaptor = createAdapter(messageClass, f)
               replyTo.foreach(_ ! adaptor.unsafeUpcast)
               Behaviors.same
             case Log(what) =>
diff --git a/actor-tests/src/test/java/org/apache/pekko/actor/AbstractFSMActorTest.java b/actor-tests/src/test/java/org/apache/pekko/actor/AbstractFSMActorTest.java
@@ -19,6 +19,7 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.RegisterExtension;
 
+@SuppressWarnings("unchecked")
 public class AbstractFSMActorTest {
 
   // javac produces an `unchecked` warning about `akka$actor$FSM$$transitionEvent`
diff --git a/actor-typed-tests/src/test/java/jdocs/org/apache/pekko/typed/Aggregator.java b/actor-typed-tests/src/test/java/jdocs/org/apache/pekko/typed/Aggregator.java
@@ -26,6 +26,7 @@
 import org.apache.pekko.actor.typed.javadsl.Behaviors;
 import org.apache.pekko.actor.typed.javadsl.Receive;
 
+@SuppressWarnings("unchecked")
 public class Aggregator<Reply, Aggregate> extends AbstractBehavior<Aggregator.Command> {
 
   interface Command {}
diff --git a/actor-typed-tests/src/test/java/jdocs/org/apache/pekko/typed/TailChopping.java b/actor-typed-tests/src/test/java/jdocs/org/apache/pekko/typed/TailChopping.java
@@ -24,6 +24,7 @@
 import org.apache.pekko.actor.typed.javadsl.Receive;
 import org.apache.pekko.actor.typed.javadsl.TimerScheduler;
 
+@SuppressWarnings("unchecked")
 public class TailChopping<Reply> extends AbstractBehavior<TailChopping.Command> {
 
   interface Command {}
diff --git a/actor-typed-tests/src/test/scala/org/apache/pekko/actor/typed/ActorContextSpec.scala b/actor-typed-tests/src/test/scala/org/apache/pekko/actor/typed/ActorContextSpec.scala
@@ -661,7 +661,8 @@ abstract class ActorContextSpec extends ScalaTestWithActorTestKit with AnyWordSp
 
     "not allow null messages" in {
       // Scala 3 doesn't generate an implicit `ClassTag[Null]` (https://github.com/lampepfl/dotty/issues/9586)
-      val actor = spawn(decoration[Null](ClassTag.Null).apply(Behaviors.empty[Null]))
+      implicit val classTag: ClassTag[Null] = ClassTag.Null
+      val actor = spawn(decoration[Null].apply(Behaviors.empty[Null]))
       intercept[InvalidMessageException] {
         actor ! null
       }
diff --git a/actor-typed/src/main/scala/org/apache/pekko/actor/typed/javadsl/Behaviors.scala b/actor-typed/src/main/scala/org/apache/pekko/actor/typed/javadsl/Behaviors.scala
@@ -234,8 +234,10 @@ object Behaviors {
    * @param monitor The messages will also be sent to this `ActorRef`
    * @param behavior The inner behavior that is decorated
    */
-  def monitor[T](interceptMessageClass: Class[T], monitor: ActorRef[T], behavior: Behavior[T]): Behavior[T] =
-    scaladsl.Behaviors.monitor(monitor, behavior)(ClassTag(interceptMessageClass))
+  def monitor[T](interceptMessageClass: Class[T], monitor: ActorRef[T], behavior: Behavior[T]): Behavior[T] = {
+    implicit val classTag: ClassTag[T] = ClassTag(interceptMessageClass)
+    scaladsl.Behaviors.monitor(monitor, behavior)
+  }
 
   /**
    * Behavior decorator that logs all messages to the [[pekko.actor.typed.Behavior]] using the provided
@@ -332,8 +334,10 @@ object Behaviors {
   def transformMessages[Outer, Inner](
       interceptMessageClass: Class[Outer],
       behavior: Behavior[Inner],
-      selector: JFunction[PFBuilder[Outer, Inner], PFBuilder[Outer, Inner]]): Behavior[Outer] =
-    BehaviorImpl.transformMessages(behavior, selector.apply(new PFBuilder).build())(ClassTag(interceptMessageClass))
+      selector: JFunction[PFBuilder[Outer, Inner], PFBuilder[Outer, Inner]]): Behavior[Outer] = {
+    implicit val classTag: ClassTag[Outer] = ClassTag(interceptMessageClass)
+    BehaviorImpl.transformMessages(behavior, selector.apply(new PFBuilder).build())
+  }
 
   /**
    * Support for scheduled `self` messages in an actor.
@@ -413,7 +417,8 @@ object Behaviors {
         asScalaMap(mdcForMessage.apply(message))
       }
 
-    WithMdcBehaviorInterceptor[T](asScalaMap(staticMdc), mdcForMessageFun, behavior)(ClassTag(interceptMessageClass))
+    implicit val classTag: ClassTag[T] = ClassTag(interceptMessageClass)
+    WithMdcBehaviorInterceptor[T](asScalaMap(staticMdc), mdcForMessageFun, behavior)
   }
 
 }
diff --git a/docs/src/test/java/jdocs/actor/ActorDocTest.java b/docs/src/test/java/jdocs/actor/ActorDocTest.java
@@ -61,6 +61,7 @@
 
 // #import-terminated
 
+@SuppressWarnings("unchecked")
 public class ActorDocTest extends AbstractJavaTest {
 
   public static Config config =
diff --git a/docs/src/test/java/jdocs/persistence/LambdaPersistencePluginDocTest.java b/docs/src/test/java/jdocs/persistence/LambdaPersistencePluginDocTest.java
@@ -35,6 +35,7 @@
 // #plugin-imports
 import org.iq80.leveldb.util.FileUtils;
 
+@SuppressWarnings({ "deprecation", "unchecked" })
 public class LambdaPersistencePluginDocTest {
 
   static Object o1 =
diff --git a/persistence/src/test/java/org/apache/pekko/persistence/fsm/AbstractPersistentFSMTest.java b/persistence/src/test/java/org/apache/pekko/persistence/fsm/AbstractPersistentFSMTest.java
@@ -20,6 +20,7 @@
 import org.apache.pekko.actor.*;
 
 @Deprecated
+@SuppressWarnings("unchecked")
 public class AbstractPersistentFSMTest {
   // tests have been removed because of flaky test failures, see PR
   // https://github.com/akka/akka/pull/31128
diff --git a/project/JdkOptions.scala b/project/JdkOptions.scala
@@ -37,7 +37,10 @@ object JdkOptions extends AutoPlugin {
 
   def targetJdkScalacOptions(scalaVersion: String): Seq[String] =
     Seq("-release", JdkOptions.targetJavaVersion) ++ {
-      if (scalaVersion.startsWith("3.")) Seq(s"-Xtarget:${targetJavaVersion}") else Seq.empty
+      CrossVersion.partialVersion(scalaVersion) match {
+        case Some((3, minor)) if minor < 8 => Seq(s"-Xtarget:${targetJavaVersion}")
+        case _                            => Seq.empty
+      }
     }
 
   val targetJdkJavacOptions = Seq("--release", targetJavaVersion)
diff --git a/project/PekkoBuild.scala b/project/PekkoBuild.scala
@@ -89,6 +89,16 @@ object PekkoBuild {
 
   private def allWarnings: Boolean = System.getProperty("pekko.allwarnings", "false").toBoolean
 
+  private def isScala38OrLater(scalaVersion: String): Boolean =
+    CrossVersion.partialVersion(scalaVersion).exists {
+      case (3, minor) if minor >= 8 => true
+      case _                        => false
+    }
+
+  private def testJavacOptions(scalaVersion: String): Seq[String] =
+    if (isScala38OrLater(scalaVersion)) Seq("-encoding", "UTF-8", "-nowarn", "-Xlint:none")
+    else DefaultJavacOptions
+
   final val DefaultScalacOptions = Def.setting {
     if (scalaVersion.value.startsWith("3.")) {
       Seq(
@@ -97,8 +107,9 @@ object PekkoBuild {
         "-feature",
         "-unchecked",
         // 'blessed' since 2.13.1
-        "-language:higherKinds",
-        "-Yfuture-lazy-vals")
+        "-language:higherKinds") ++
+      (if (isScala38OrLater(scalaVersion.value)) Seq("-Wconf:any:s") else Seq.empty) ++
+      (if (scalaVersion.value.startsWith("3.3.")) Seq("-Yfuture-lazy-vals") else Seq.empty)
     } else {
       Seq(
         "-encoding",
@@ -127,7 +138,7 @@ object PekkoBuild {
     Test / scalacOptions := (Test / scalacOptions).value.filterNot(opt =>
       opt == "-Xlog-reflective-calls" || opt.contains("genjavadoc")),
     Compile / javacOptions ++= JdkOptions.targetJdkJavacOptions,
-    Test / javacOptions ++= DefaultJavacOptions ++ JdkOptions.targetJdkJavacOptions,
+    Test / javacOptions ++= testJavacOptions(scalaVersion.value) ++ JdkOptions.targetJdkJavacOptions,
     Compile / javacOptions ++= (if (allWarnings) Seq("-Xlint:deprecation") else Nil),
     doc / javacOptions := Seq(),
     crossVersion := CrossVersion.binary,
diff --git a/stream-tests/src/test/java/org/apache/pekko/stream/javadsl/FlowTest.java b/stream-tests/src/test/java/org/apache/pekko/stream/javadsl/FlowTest.java
@@ -53,7 +53,7 @@
 import org.junit.jupiter.api.extension.RegisterExtension;
 import org.reactivestreams.Publisher;
 
-@SuppressWarnings("serial")
+@SuppressWarnings({ "serial", "unchecked" })
 public class FlowTest extends StreamTestJupiter {
   public FlowTest() {
     super(actorSystemResource);
diff --git a/stream/src/main/scala/org/apache/pekko/stream/impl/fusing/Ops.scala b/stream/src/main/scala/org/apache/pekko/stream/impl/fusing/Ops.scala
@@ -1658,7 +1658,8 @@ private[stream] object Collect {
         log = logAdapter match {
           case Some(l) => l
           case _       =>
-            Logging(materializer.system, materializer)(fromMaterializer)
+            implicit val logSource: LogSource[Materializer] = Log.fromMaterializer
+            Logging(materializer.system, materializer)
         }
       }
 
@@ -1778,7 +1779,8 @@ private[stream] object Collect {
         log = logAdapter match {
           case Some(l) => l
           case _       =>
-            Logging.withMarker(materializer.system, materializer)(fromMaterializer)
+            implicit val logSource: LogSource[Materializer] = LogWithMarker.fromMaterializer
+            Logging.withMarker(materializer.system, materializer)
         }
       }
 
diff --git a/stream/src/main/scala/org/apache/pekko/stream/impl/io/InputStreamSinkStage.scala b/stream/src/main/scala/org/apache/pekko/stream/impl/io/InputStreamSinkStage.scala
@@ -13,7 +13,7 @@
 
 package org.apache.pekko.stream.impl.io
 
-import java.io.{ IOException, InputStream }
+import _root_.java.io.{ IOException, InputStream => JavaInputStream }
 import java.util.concurrent.{ BlockingQueue, LinkedBlockingDeque, TimeUnit }
 import java.util.concurrent.atomic.AtomicBoolean
 
@@ -51,13 +51,13 @@ private[stream] object InputStreamSinkStage {
  * INTERNAL API
  */
 @InternalApi final private[stream] class InputStreamSinkStage(readTimeout: FiniteDuration)
-    extends GraphStageWithMaterializedValue[SinkShape[ByteString], InputStream] {
+    extends GraphStageWithMaterializedValue[SinkShape[ByteString], JavaInputStream] {
 
   val in = Inlet[ByteString]("InputStreamSink.in")
   override def initialAttributes: Attributes = DefaultAttributes.inputStreamSink
   override val shape: SinkShape[ByteString] = SinkShape.of(in)
 
-  override def createLogicAndMaterializedValue(inheritedAttributes: Attributes): (GraphStageLogic, InputStream) = {
+  override def createLogicAndMaterializedValue(inheritedAttributes: Attributes): (GraphStageLogic, JavaInputStream) = {
     val maxBuffer = inheritedAttributes.get[InputBuffer](InputBuffer(16, 16)).max
     require(maxBuffer > 0, "Buffer size must be greater than 0")
 
@@ -126,7 +126,7 @@ private[stream] object InputStreamSinkStage {
     sharedBuffer: BlockingQueue[StreamToAdapterMessage],
     sendToStage: (AdapterToStageMessage) => Unit,
     readTimeout: FiniteDuration)
-    extends InputStream {
+    extends JavaInputStream {
 
   var isInitialized = false
   val isActive = new AtomicBoolean(true)
diff --git a/stream/src/main/scala/org/apache/pekko/stream/impl/io/OutputStreamSourceStage.scala b/stream/src/main/scala/org/apache/pekko/stream/impl/io/OutputStreamSourceStage.scala
@@ -13,7 +13,7 @@
 
 package org.apache.pekko.stream.impl.io
 
-import java.io.{ IOException, OutputStream }
+import _root_.java.io.{ IOException, OutputStream => JavaOutputStream }
 import java.util.concurrent.{ Semaphore, TimeUnit }
 
 import scala.concurrent.Await
@@ -35,12 +35,12 @@ private[stream] object OutputStreamSourceStage {
 }
 
 final private[stream] class OutputStreamSourceStage(writeTimeout: FiniteDuration)
-    extends GraphStageWithMaterializedValue[SourceShape[ByteString], OutputStream] {
+    extends GraphStageWithMaterializedValue[SourceShape[ByteString], JavaOutputStream] {
   val out = Outlet[ByteString]("OutputStreamSource.out")
   override def initialAttributes = DefaultAttributes.outputStreamSource
   override val shape: SourceShape[ByteString] = SourceShape.of(out)
 
-  override def createLogicAndMaterializedValue(inheritedAttributes: Attributes): (GraphStageLogic, OutputStream) = {
+  override def createLogicAndMaterializedValue(inheritedAttributes: Attributes): (GraphStageLogic, JavaOutputStream) = {
     val maxBuffer = inheritedAttributes.get[InputBuffer](InputBuffer(16, 16)).max
 
     require(maxBuffer > 0, "Buffer size must be greater than 0")
@@ -78,7 +78,7 @@ private[pekko] class OutputStreamAdapter(
     unfulfilledDemand: Semaphore,
     sendToStage: AsyncCallback[AdapterToStageMessage],
     writeTimeout: FiniteDuration)
-    extends OutputStream {
+    extends JavaOutputStream {
 
   @scala.throws(classOf[IOException])
   private def sendData(data: ByteString): Unit = {

Original file line number	Diff line number	Diff line change
`@@ -661,7 +661,8 @@ abstract class ActorContextSpec extends ScalaTestWithActorTestKit with AnyWordSp`
`661`	`661`
`662`	`662`	`"not allow null messages" in {`
`663`	`663`	// Scala 3 doesn't generate an implicit `ClassTag[Null]` (https://github.com/lampepfl/dotty/issues/9586)
`664`		`- val actor = spawn(decoration[Null](ClassTag.Null).apply(Behaviors.empty[Null]))`
	`664`	`+ implicit val classTag: ClassTag[Null] = ClassTag.Null`
	`665`	`+ val actor = spawn(decoration[Null].apply(Behaviors.empty[Null]))`
`665`	`666`	`intercept[InvalidMessageException] {`
`666`	`667`	`actor ! null`
`667`	`668`	`}`