Enable direct usage of --repl-init-script with Scala REPL >= 3.6.4-RC1

modules/cli/src/main/scala/scala/cli/commands/repl/Repl.scala

@@ -4,6 +4,7 @@ import ai.kien.python.Python
 import caseapp.*
 import caseapp.core.help.HelpFormat
 import coursier.cache.FileCache
+import coursier.core.Version
 import coursier.error.{FetchError, ResolutionError}
 import dependency.*
 
@@ -20,6 +21,7 @@ import scala.build.errors.{
 }
 import scala.build.input.Inputs
 import scala.build.internal.{Constants, Runner}
+import scala.build.options.ScalacOpt.noDashPrefixes
 import scala.build.options.{BuildOptions, JavaOpt, MaybeScalaVersion, Scope}
 import scala.cli.commands.publish.ConfigUtil.*
 import scala.cli.commands.run.Run.{
@@ -28,14 +30,14 @@ import scala.cli.commands.run.Run.{
   pythonPathEnv
 }
 import scala.cli.commands.run.RunMode
-import scala.cli.commands.shared.{HelpCommandGroup, HelpGroup, SharedOptions}
+import scala.cli.commands.shared.{HelpCommandGroup, HelpGroup, ScalacOptions, SharedOptions}
 import scala.cli.commands.util.BuildCommandHelpers
 import scala.cli.commands.{ScalaCommand, WatchUtil}
 import scala.cli.config.{ConfigDb, Keys}
 import scala.cli.packaging.Library
 import scala.cli.util.ArgHelpers.*
 import scala.cli.util.ConfigDbUtils
-import scala.cli.{CurrentParams, ScalaCli}
+import scala.cli.{CurrentParams, ScalaCli, coursierVersion}
 import scala.jdk.CollectionConverters.*
 import scala.util.Properties
 
@@ -390,11 +392,24 @@ object Repl extends ScalaCommand[ReplOptions] with BuildCommandHelpers {
       replArgs: Seq[String],
       extraEnv: Map[String, String] = Map.empty,
       extraProps: Map[String, String] = Map.empty
-    ): Unit =
-      if (dryRun)
-        logger.message("Dry run, not running REPL.")
+    ): Unit = {
+      val isAmmonite = replArtifacts.replMainClass.startsWith("ammonite")
+      if replArgs.exists(_.noDashPrefixes == ScalacOptions.replInitScript) then
+        scalaParams.scalaVersion match
+          case _ if isAmmonite =>
+            logger.message(
+              "The '--repl-init-script' option is not supported with Ammonite. Did you mean to use '--ammonite-arg'?"
+            )
+          case s
+              if s.coursierVersion < "3.6.4-RC1".coursierVersion &&
+              s.coursierVersion < "3.6.4".coursierVersion &&
+              s.coursierVersion < "3.6.4-RC1-bin-20250109-a50a1e4-NIGHTLY".coursierVersion =>
+            logger.message(
+              "The '--repl-init-script option' is only supported starting with Scala 3.6.4 and onwards."
+            )
+          case _ => ()
+      if dryRun then logger.message("Dry run, not running REPL.")
       else {
-        val isAmmonite = replArtifacts.replMainClass.startsWith("ammonite")
         val depClassPathArgs: Seq[String] =
           if replArtifacts.depsClassPath.nonEmpty && !isAmmonite then
             Seq(
@@ -422,6 +437,7 @@ object Repl extends ScalaCommand[ReplOptions] with BuildCommandHelpers {
         if (retCode != 0)
           value(Left(new ReplError(retCode)))
       }
+    }
 
     def defaultArtifacts(): Either[BuildException, ReplArtifacts] = either {
       value {

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

@@ -48,6 +48,8 @@ object ScalacOptions {
   val YScriptRunnerOption               = "Yscriptrunner"
   private val scalacOptionsPurePrefixes = Set("V", "W", "X", "Y")
   private val scalacOptionsPrefixes     = Set("P") ++ scalacOptionsPurePrefixes
+  val replInitScript                    = "repl-init-script"
+  private val replAliasedOptions        = Set(replInitScript)
   private val scalacAliasedOptions = // these options don't require being passed after -O and accept an arg
     Set(
       "coverage-exclude-classlikes",
@@ -61,7 +63,7 @@ object ScalacOptions {
       "target",
       "source",
       YScriptRunnerOption
-    )
+    ) ++ replAliasedOptions
   private val scalacNoArgAliasedOptions = // these options don't require being passed after -O and don't accept an arg
     Set(
       "experimental",

modules/cli/src/main/scala/scala/cli/package.scala

@@ -0,0 +1,7 @@
+package scala
+
+import coursier.core.Version
+
+package object cli {
+  extension (s: String) def coursierVersion: Version = Version(s)
+}

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

@@ -86,4 +86,26 @@ abstract class ReplTestDefinitions extends ScalaCliSuite with TestScalaVersionAr
       expect(res.exitCode == 0)
     }
   }
+
+  test("--repl-init-script dry run") {
+    TestInputs.empty.fromRoot { root =>
+      val r = os.proc(
+        TestUtil.cli,
+        "repl",
+        extraOptions,
+        "--repl-init-script",
+        "println(\"Hello\")",
+        "--repl-dry-run"
+      )
+        .call(cwd = root, stderr = os.Pipe, check = false)
+      val warningText =
+        "The '--repl-init-script option' is only supported starting with Scala 3.6.4 and onwards."
+      val coursierScalaVersion = actualScalaVersion.coursierVersion
+      val shouldPrintWarning = coursierScalaVersion < "3.6.4".coursierVersion &&
+        coursierScalaVersion < "3.6.4-RC1".coursierVersion &&
+        coursierScalaVersion < "3.6.4-RC1-bin-20250109-a50a1e4-NIGHTLY".coursierVersion
+      if (shouldPrintWarning) expect(r.err.trim().contains(warningText))
+      else expect(!r.err.trim().contains(warningText))
+    }
+  }
 }

website/docs/commands/repl.md

@@ -80,6 +80,63 @@ scala> :quit
 
 </ChainedSnippets>
 
+## Passing REPL options
+It is also possible to manually pass REPL-specific options.
+It can be done in a couple ways:
+- after the `--` separator, as the REPL itself is the launched app, so its options are app arguments
+
+<ChainedSnippets>
+
+```bash ignore
+scala repl -S 3.6.4-RC1 -- --repl-init-script 'println("Hello")'
+```
+
+```
+Hello
+Welcome to Scala 3.6.4-RC1 (23.0.1, Java OpenJDK 64-Bit Server VM).
+Type in expressions for evaluation. Or try :help.
+
+scala> 
+```
+</ChainedSnippets>
+
+
+- with the `-O`, effectively passing them as compiler options:
+
+<ChainedSnippets>
+
+```bash ignore
+scala repl -S 3.6.4-RC1 -O --repl-init-script -O 'println("Hello")'
+```
+
+```
+Hello
+Welcome to Scala 3.6.4-RC1 (23.0.1, Java OpenJDK 64-Bit Server VM).
+Type in expressions for evaluation. Or try :help.
+
+scala> 
+```
+
+</ChainedSnippets>
+
+- directly, as a Scala CLI option (do note that newly added options from an RC version or a snapshot may not be supported this way just yet):
+
+<ChainedSnippets>
+
+```bash ignore
+scala repl -S 3.6.4-RC1 --repl-init-script 'println("Hello")'
+```
+
+```
+Hello
+Welcome to Scala 3.6.4-RC1 (23.0.1, Java OpenJDK 64-Bit Server VM).
+Type in expressions for evaluation. Or try :help.
+
+scala> 
+```
+
+</ChainedSnippets>
+
 ## Using Toolkit in REPL
 It is also possible to start the scala-cli REPL with [toolkit](https://scala-cli.virtuslab.org/docs/guides/introduction/toolkit/) enabled