Ensure --cli-default-scala-version is respected by --scalac-help (#3048)

Author: Gedochao

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

@@ -192,14 +192,17 @@ abstract class ScalaCommand[T <: HasGlobalOptions](implicit myParser: Parser[T],
       updatedScalacOptions = scalacOptions.withScalacExtraOptions(shared.scalacExtra)
       if updatedScalacOptions.exists(ScalacOptions.ScalacPrintOptions)
       logger = shared.logger
-      artifacts      <- buildOptions.artifacts(logger, Scope.Main).toOption
+      fixedBuildOptions = buildOptions.copy(scalaOptions =
+        buildOptions.scalaOptions.copy(defaultScalaVersion = Some(ScalaCli.getDefaultScalaVersion))
+      )
+      artifacts      <- fixedBuildOptions.artifacts(logger, Scope.Main).toOption
       scalaArtifacts <- artifacts.scalaOpt
       compilerClassPath   = scalaArtifacts.compilerClassPath
       scalaVersion        = scalaArtifacts.params.scalaVersion
       compileClassPath    = artifacts.compileClassPath
       simpleScalaCompiler = SimpleScalaCompiler("java", Nil, scaladoc = false)
-      javacOptions        = buildOptions.javaOptions.javacOptions.map(_.value)
-      javaHome            = buildOptions.javaHomeLocation().value
+      javacOptions        = fixedBuildOptions.javaOptions.javacOptions.map(_.value)
+      javaHome            = fixedBuildOptions.javaHomeLocation().value
     } {
       val exitCode = simpleScalaCompiler.runSimpleScalacLike(
         scalaVersion,

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

@@ -906,4 +906,19 @@ class SipScalaTests extends ScalaCliSuite with SbtTestHelper with MillTestHelper
         expect(r.out.trim() == sv)
       }
     }
+
+  test("scalac help respects --cli-default-scala-version") {
+    TestInputs.empty.fromRoot { root =>
+      val sv = Constants.scala3NextRc
+      val launcherVersionOverrideHelp =
+        os.proc(TestUtil.cli, "--cli-default-scala-version", sv, "--scalac-help")
+          .call(cwd = root).out.trim()
+      val standardVersionOverrideHelp =
+        os.proc(TestUtil.cli, "--scalac-help", "-S", sv)
+          .call(cwd = root).out.trim()
+      val migrationPrefix = sv.take(2) + (sv.charAt(2).asDigit + 1).toString
+      expect(launcherVersionOverrideHelp.contains(s"$migrationPrefix-migration"))
+      expect(launcherVersionOverrideHelp == standardVersionOverrideHelp)
+    }
+  }
 }