Use enumeration for Scala 2 library TASTy setting

.github/workflows/ci.yaml

@@ -143,10 +143,10 @@ jobs:
           ./project/scripts/sbt ";sjsSandbox/run ;sjsSandbox/test ;sjsJUnitTests/test ;set sjsJUnitTests/scalaJSLinkerConfig ~= switchToESModules ;sjsJUnitTests/test ;sjsCompilerTests/test"
 
       - name: Test with Scala 2 library TASTy
-        run: ./project/scripts/sbt ";set ThisBuild/Build.useScala2LibraryTasty := true ;scala3-bootstrapped/testCompilation i5; scala3-bootstrapped/testCompilation tests/run/typelevel-peano.scala" # only test a subset of test to avoid doubling the CI execution time
+        run: ./project/scripts/sbt ";set ThisBuild/Build.scala2Library := Build.Scala2LibraryTasty ;scala3-bootstrapped/testCompilation i5; scala3-bootstrapped/testCompilation tests/run/typelevel-peano.scala" # only test a subset of test to avoid doubling the CI execution time
 
       - name: Test with Scala 2 library TASTy with CC
-        run: ./project/scripts/sbt ";set ThisBuild/Build.useScala2LibraryCCTasty := true ;scala3-bootstrapped/testCompilation i5; scala3-bootstrapped/testCompilation tests/run/typelevel-peano.scala" # only test a subset of test to avoid doubling the CI execution time
+        run: ./project/scripts/sbt ";set ThisBuild/Build.scala2Library := Build.Scala2LibraryCCTasty ;scala3-bootstrapped/testCompilation i5; scala3-bootstrapped/testCompilation tests/run/typelevel-peano.scala" # only test a subset of test to avoid doubling the CI execution time
 
   test_windows_fast:
     runs-on: [self-hosted, Windows]

project/Build.scala

@@ -173,17 +173,23 @@ object Build {
   // Run tests with filter through vulpix test suite
   val testCompilation = inputKey[Unit]("runs integration test with the supplied filter")
 
+  sealed trait Scala2Library
+  // Use Scala 2 compiled library JAR
+  object Scala2LibraryJar extends Scala2Library
   // Use the TASTy jar from `scala2-library-tasty` in the classpath
   // This only works with `scala3-bootstrapped/scalac` and tests in `scala3-bootstrapped`
   //
-  // Enable in SBT with: `set ThisBuild/Build.useScala2LibraryTasty := true`
-  val useScala2LibraryTasty = settingKey[Boolean]("Use the TASTy jar from `scala2-library-tasty` in the classpath")
-
+  object Scala2LibraryTasty extends Scala2Library
   // Use the TASTy jar from `scala2-library-cc-tasty` in the classpath
   // This only works with `scala3-bootstrapped/scalac` and tests in `scala3-bootstrapped`
   //
-  // Enable in SBT with: `set ThisBuild/Build.useScala2LibraryCCTasty := true`
-  val useScala2LibraryCCTasty = settingKey[Boolean]("Use the TASTy jar from `scala2-library-cc-tasty` in the classpath")
+  object Scala2LibraryCCTasty extends Scala2Library
+
+  // Set in SBT with:
+  //   - `set ThisBuild/Build.scala2Library := Build.Scala2LibraryJar` (default)
+  //   - `set ThisBuild/Build.scala2Library := Build.Scala2LibraryTasty`
+  //   - `set ThisBuild/Build.scala2Library := Build.Scala2LibraryCCTasty`
+  val scala2Library = settingKey[Scala2Library]("Choose which version of the Scala 2 library should be used")
 
   // Used to compile files similar to ./bin/scalac script
   val scalac = inputKey[Unit]("run the compiler using the correct classpath, or the user supplied classpath")
@@ -231,8 +237,7 @@ object Build {
 
     outputStrategy := Some(StdoutOutput),
 
-    useScala2LibraryTasty := false,
-    useScala2LibraryCCTasty := false,
+    scala2Library := Scala2LibraryJar,
 
     // enable verbose exception messages for JUnit
     (Test / testOptions) += Tests.Argument(TestFrameworks.JUnit, "-a", "-v", "-s"),
@@ -652,26 +657,21 @@ object Build {
         val externalDeps = externalCompilerClasspathTask.value
         val jars = packageAll.value
 
-        val scala2LibraryTasty = jars.get("scala2-library-tasty") match {
-          case Some(scala2LibraryTastyJar) if useScala2LibraryTasty.value =>
-            Seq("-Ddotty.tests.tasties.scalaLibrary=" + scala2LibraryTastyJar)
-          case _ =>
-            if (useScala2LibraryTasty.value) log.warn("useScala2LibraryTasty is ignored on non-bootstrapped compiler")
-            Seq.empty
-        }
-
-        val scala2LibraryCCTasty = jars.get("scala2-library-cc-tasty") match {
-          case Some(scala2LibraryCCTastyJar) if useScala2LibraryCCTasty.value =>
-            if (useScala2LibraryTasty.value) {
-              log.warn("Both useScala2LibraryTasty and useScala2LibraryCCTasty are set (ignoring useScala2LibraryCCTasty)")
-              Seq.empty
-            } else Seq("-Ddotty.tests.tasties.scalaLibrary=" + scala2LibraryCCTastyJar)
-          case _ =>
-            if (useScala2LibraryCCTasty.value) log.warn("useScala2LibraryCCTasty is ignored on non-bootstrapped compiler")
-            Seq.empty
+        def libraryPathProperty(jarName: String): Seq[String] =
+          jars.get(jarName) match {
+              case Some(jar) =>
+                Seq(s"-Ddotty.tests.tasties.scalaLibrary=$jar")
+              case None =>
+                log.warn("Scala 2 library TASTy is ignored on non-bootstrapped compiler")
+                Seq.empty
+            }
+        val scala2LibraryTasty = scala2Library.value match {
+          case Scala2LibraryJar => Seq.empty
+          case Scala2LibraryTasty => libraryPathProperty("scala2-library-tasty")
+          case Scala2LibraryTastyCC => libraryPathProperty("scala2-library-cc-tasty")
         }
 
-        scala2LibraryTasty ++ scala2LibraryCCTasty ++ Seq(
+        scala2LibraryTasty ++ Seq(
           "-Ddotty.tests.dottyCompilerManagedSources=" + managedSrcDir,
           "-Ddotty.tests.classes.dottyInterfaces=" + jars("scala3-interfaces"),
           "-Ddotty.tests.classes.dottyLibrary=" + jars("scala3-library"),
@@ -776,14 +776,12 @@ object Build {
           else if (debugFromTasty) "dotty.tools.dotc.fromtasty.Debug"
           else "dotty.tools.dotc.Main"
 
-        var extraClasspath =
-          scalaLibTastyOpt match {
-            case Some(scalaLibTasty) if useScala2LibraryTasty.value =>
-              Seq(scalaLibTasty, scalaLib, dottyLib)
-            case _ =>
-              if (useScala2LibraryTasty.value) log.warn("useScala2LibraryTasty is ignored on non-bootstrapped compiler")
-              Seq(scalaLib, dottyLib)
-          }
+        val scala2LibraryTasty = scala2Library.value match {
+          case Scala2LibraryJar => Seq.empty
+          case Scala2LibraryTasty => jars.get("scala2-library-tasty").toSeq
+          case Scala2LibraryTastyCC => jars.get("scala2-library-cc-tasty").toSeq
+        }
+        var extraClasspath = scala2LibraryTasty ++ Seq(scalaLib, dottyLib)
 
         if (decompile && !args.contains("-classpath"))
           extraClasspath ++= Seq(".")