feat: Add scala-cli script generator to verify jdk classes

build.sbt

@@ -434,6 +434,7 @@ lazy val stream = pekkoModule("stream")
   .settings(AutomaticModuleName.settings("pekko.stream"))
   .settings(OSGi.stream)
   .settings(Protobuf.settings)
+  .settings(VerifyJDK9Classes.settings)
   .enablePlugins(BoilerplatePlugin, Jdk9)
 
 lazy val streamTestkit = pekkoModule("stream-testkit")

project/VerifyJDK9Classes.scala

@@ -0,0 +1,56 @@
+
+
+object VerifyJDK9Classes {
+  import sbt.*
+  import sbt.Keys.*
+
+  lazy val settings: Seq[Setting[_]] = inConfig(Compile) {
+    Seq {
+      sourceGenerators += {
+        generateAndWriteScalaCLIScript(
+          target,
+          _ / "scala-cli" / "VerifyJDK9Classes.sc")
+      }
+    }
+  }
+
+  def generateAndWriteScalaCLIScript(dir: SettingKey[File], locate: File => File): Def.Initialize[Task[Seq[sbt.File]]] =
+    Def.task[Seq[File]] {
+      val script = generateScalaCLIScript(version.value)
+      val file = locate(dir.value)
+      val content = script.stripMargin.format(version.value)
+      if (!file.exists || IO.read(file) != content) IO.write(file, content)
+      //the generated file is not used.
+      Nil
+    }
+
+  private def generateScalaCLIScript(version: String): String =
+    s"""
+      |//> using repository m2Local
+      |//> using repository sonatype:snapshots
+      |//> using repository sonatype:releases
+      |//> using dep "org.apache.pekko::pekko-stream:${version}"
+      |////> using jvm 11
+      |object VerifyJDK9Classes {
+      |  def main(args: Array[String]): Unit = {
+      |    import org.apache.pekko.actor.ActorSystem
+      |    import org.apache.pekko.stream.scaladsl.{ JavaFlowSupport, Source }
+      |
+      |    import java.lang.System.exit
+      |    import scala.concurrent.Await
+      |    import scala.concurrent.duration.DurationInt
+      |    implicit val system: ActorSystem = ActorSystem.create("test")
+      |    val future = Source(1 to 3).runWith(
+      |      JavaFlowSupport.Sink.asPublisher[Int](fanout = false).mapMaterializedValue { p =>
+      |        JavaFlowSupport.Source.fromPublisher(p).runFold(0)(_ + _)
+      |      })
+      |
+      |    val result = Await.result(future, 3.seconds)
+      |    println(s"Result:" + result)
+      |    system.terminate()
+      |    exit(if (result == 6) 0 else 1)
+      |  }
+      |}
+      |
+      |""".stripMargin
+}