Add warnings for the deprecated -Yscriptrunner legacy scala runner option instead of passing it to scalac

modules/cli/src/main/scala/scala/cli/commands/ScalaCommand.scala

@@ -15,8 +15,9 @@ import scala.build.EitherCps.{either, value}
 import scala.build.compiler.SimpleScalaCompiler
 import scala.build.errors.BuildException
 import scala.build.internal.{Constants, Runner}
-import scala.build.options.{BuildOptions, Scope}
+import scala.build.options.{BuildOptions, ScalacOpt, Scope}
 import scala.build.{Artifacts, Logger, Positioned, ReplArtifacts}
+import scala.cli.commands.default.LegacyScalaOptions
 import scala.cli.commands.shared.{HasLoggingOptions, ScalaCliHelp, ScalacOptions, SharedOptions}
 import scala.cli.commands.util.CommandHelpers
 import scala.cli.commands.util.ScalacOptionsUtil.*
@@ -133,6 +134,18 @@ abstract class ScalaCommand[T <: HasLoggingOptions](implicit myParser: Parser[T]
     for (shared <- sharedOptions(options))
       shared.helpGroups.maybePrintGroupHelp(help, helpFormat)
 
+  private def maybePrintWarnings(options: T): Unit = {
+    import scala.cli.commands.shared.ScalacOptions.YScriptRunnerOption
+    val logger = options.logging.logger
+    sharedOptions(options).foreach { so =>
+      val scalacOpts = so.scalac.scalacOption.toScalacOptShadowingSeq
+      if scalacOpts.keys.contains(ScalacOpt(YScriptRunnerOption)) then
+        logger.message(
+          LegacyScalaOptions.yScriptRunnerWarning(scalacOpts.getOption(YScriptRunnerOption))
+        )
+    }
+  }
+
   /** Print `scalac` output if passed options imply no inputs are necessary and raw `scalac` output
     * is required instead. (i.e. `--scalac-option -help`)
     * @param options
@@ -265,6 +278,7 @@ abstract class ScalaCommand[T <: HasLoggingOptions](implicit myParser: Parser[T]
     */
   final override def run(options: T, remainingArgs: RemainingArgs): Unit = {
     CurrentParams.verbosity = options.logging.verbosity
+    maybePrintWarnings(options)
     maybePrintGroupHelp(options)
     buildOptions(options).foreach { bo =>
       maybePrintSimpleScalacOutput(options, bo)

modules/cli/src/main/scala/scala/cli/commands/default/LegacyScalaOptions.scala

@@ -5,9 +5,11 @@ import caseapp.core.Indexed
 
 import scala.build.Logger
 import scala.cli.ScalaCli
-import scala.cli.ScalaCli.fullRunnerName
+import scala.cli.ScalaCli.{fullRunnerName, progName}
+import scala.cli.commands.bloop.BloopExit
 import scala.cli.commands.default.LegacyScalaOptions.*
 import scala.cli.commands.package0.Package
+import scala.cli.commands.shared.ScalacOptions.YScriptRunnerOption
 import scala.cli.commands.tags
 
 /** Options covering backwards compatibility with the old scala runner.
@@ -164,4 +166,26 @@ object LegacyScalaOptions {
 
   private[default] lazy val PowerString =
     if ScalaCli.allowRestrictedFeatures then "" else "--power "
+
+  def yScriptRunnerWarning(yScriptRunnerValue: Option[String]): String = {
+    val valueSpecificMsg = yScriptRunnerValue match {
+      case Some(v @ "default") =>
+        s"scala.tools.nsc.DefaultScriptRunner (the $v script runner) is no longer available."
+      case Some(v @ "resident") =>
+        s"scala.tools.nsc.fsc.ResidentScriptRunner (the $v script runner) is no longer available."
+      case Some(v @ "shutdown") =>
+        val bloopExitCommandName =
+          BloopExit.names.headOption.map(_.mkString(" ")).getOrElse(BloopExit.name)
+        s"""scala.tools.nsc.fsc.DaemonKiller (the $v script runner) is no longer available.
+           |Did you want to stop the $fullRunnerName build server (Bloop) instead?
+           |If so, consider using the following command:
+           |  ${Console.BOLD}$progName $PowerString$bloopExitCommandName${Console.RESET}""".stripMargin
+      case Some(className) =>
+        s"Using $className as the script runner is no longer supported and will not be attempted."
+      case _ => ""
+    }
+    s"""Deprecated option '$YScriptRunnerOption' is ignored.
+       |The script runner can no longer be picked as before.
+       |$valueSpecificMsg""".stripMargin
+  }
 }

modules/cli/src/main/scala/scala/cli/commands/shared/ScalacOptions.scala

@@ -35,12 +35,13 @@ object ScalacOptions {
     origin = Some("ScalacOptions")
   )
   // .withIsFlag(true) // The scalac options we handle accept no value after the -… argument
+  val YScriptRunnerOption = "-Yscriptrunner"
   private val scalacOptionsPurePrefixes =
     Set("-V", "-W", "-X", "-Y")
   private val scalacOptionsPrefixes =
     Set("-g", "-language", "-opt", "-P", "-target", "-source") ++ scalacOptionsPurePrefixes
   private val scalacAliasedOptions = // these options don't require being passed after -O and accept an arg
-    Set("-encoding", "-release", "-color")
+    Set("-encoding", "-release", "-color", YScriptRunnerOption)
   private val scalacNoArgAliasedOptions = // these options don't require being passed after -O and don't accept an arg
     Set(
       "-nowarn",
@@ -64,6 +65,9 @@ object ScalacOptions {
     "-classpath", // redirected to --extra-jars
     "-d"          // redirected to --compilation-output
   )
+  val ScalacDeprecatedOptions: Set[String] = Set(
+    YScriptRunnerOption // old 'scala' runner specific, no longer supported
+  )
 
   private val scalacOptionsArgument: Argument[List[String]] =
     new Argument[List[String]] {
@@ -81,7 +85,9 @@ object ScalacOptions {
         formatter: Formatter[Name]
       ): Either[(Error, List[String]), Option[(Option[List[String]], List[String])]] =
         args match {
-          case h :: t if scalacOptionsPrefixes.exists(h.startsWith) =>
+          case h :: t
+              if scalacOptionsPrefixes.exists(h.startsWith) &&
+              !ScalacDeprecatedOptions.contains(h) =>
             Right(Some((Some(h :: acc.getOrElse(Nil)), t)))
           case h :: t if scalacNoArgAliasedOptions.contains(h) =>
             Right(Some((Some(h :: acc.getOrElse(Nil)), t)))

modules/cli/src/main/scala/scala/cli/commands/shared/SharedOptions.scala

@@ -300,6 +300,7 @@ final case class SharedOptions(
           .withScalacExtraOptions(scalacExtra)
           .toScalacOptShadowingSeq
           .filterNonRedirected
+          .filterNonDeprecated
           .map(Positioned.commandLine),
         compilerPlugins =
           SharedOptions.parseDependencies(

modules/cli/src/main/scala/scala/cli/commands/util/ScalacOptionsUtil.scala

@@ -1,6 +1,10 @@
 package scala.cli.commands.util
 
+import scala.build.Logger
 import scala.build.options.{ScalacOpt, ShadowingSeq}
+import scala.cli.commands.bloop.BloopExit
+import scala.cli.commands.default.LegacyScalaOptions
+import scala.cli.commands.shared.ScalacOptions.YScriptRunnerOption
 import scala.cli.commands.shared.{ScalacExtraOptions, ScalacOptions}
 
 object ScalacOptionsUtil {
@@ -31,6 +35,8 @@ object ScalacOptionsUtil {
       opts.filterKeys(_.key.exists(f))
     def filterNonRedirected: ShadowingSeq[ScalacOpt] =
       opts.filterScalacOptionKeys(!ScalacOptions.ScalaCliRedirectedOptions.contains(_))
+    def filterNonDeprecated: ShadowingSeq[ScalacOpt] =
+      opts.filterScalacOptionKeys(!ScalacOptions.ScalacDeprecatedOptions.contains(_))
     def getOption(key: String): Option[String] =
       opts.get(ScalacOpt(key)).headOption.map(_.value)
   }

modules/integration/src/test/scala/scala/cli/integration/LegacyScalaRunnerTestDefinitions.scala

@@ -85,6 +85,26 @@ trait LegacyScalaRunnerTestDefinitions { _: DefaultTests =>
     }
   }
 
+  test("ensure -Yscriptrunner works with the default command") {
+    legacyOptionBackwardsCompatTest("-Yscriptrunner") {
+      (legacyOption, inputFile, root) =>
+        Seq("default", "resident", "shutdown", "scala.tools.nsc.fsc.ResidentScriptRunner").foreach {
+          legacyOptionValue =>
+            val res =
+              os.proc(
+                TestUtil.cli,
+                legacyOption,
+                legacyOptionValue,
+                inputFile,
+                TestUtil.extraOptions
+              )
+                .call(cwd = root, stderr = os.Pipe)
+            expect(res.err.trim().contains(deprecatedOptionWarning(legacyOption)))
+            expect(res.err.trim().contains(legacyOptionValue))
+        }
+    }
+  }
+
   private def simpleLegacyOptionBackwardsCompatTest(optionAliases: String*): Unit =
     abstractLegacyOptionBackwardsCompatTest(optionAliases) {
       (legacyOption, expectedMsg, _, root) =>

modules/options/src/main/scala/scala/build/options/ShadowingSeq.scala

@@ -20,6 +20,7 @@ final case class ShadowingSeq[T] private (values: Seq[Seq[T]]) {
       case Seq(head, _*) => f(head)
       case _             => true
     }
+  def keys: Seq[T] = values.map(_.head)
   def ++(other: Seq[T])(implicit key: ShadowingSeq.KeyOf[T]): ShadowingSeq[T] =
     addGroups(ShadowingSeq.groups(other, key.groups(other)))
   private def addGroups(other: Seq[Seq[T]])(implicit key: ShadowingSeq.KeyOf[T]): ShadowingSeq[T] =