Allow cross compilation tests with Scala 2 compiler

Author: nicolasstucki

compiler/test/dotc/run-scala-js.blacklist

@@ -0,0 +1,2 @@
+# Cross version tests (`..._c2.13.12.scala`) are not supported for Scala 2 with Scala.js.
+i18884

compiler/test/dotty/tools/TestSources.scala

@@ -27,12 +27,14 @@ object TestSources {
 
   def runFromTastyBlacklistFile: String = "compiler/test/dotc/run-from-tasty.blacklist"
   def runTestPicklingBlacklistFile: String = "compiler/test/dotc/run-test-pickling.blacklist"
+  def runScalaJSBlacklistFile: String = "compiler/test/dotc/run-scala-js.blacklist"
   def runTestRecheckExcludesFile: String = "compiler/test/dotc/run-test-recheck.excludes"
   def runLazyValsAllowlistFile: String = "compiler/test/dotc/run-lazy-vals-tests.allowlist"
 
 
   def runFromTastyBlacklisted: List[String] = loadList(runFromTastyBlacklistFile)
   def runTestPicklingBlacklisted: List[String] = loadList(runTestPicklingBlacklistFile)
+  def runScalaJSBlacklistFileBlacklisted: List[String] = loadList(runScalaJSBlacklistFile)
   def runTestRecheckExcluded: List[String] = loadList(runTestRecheckExcludesFile)
   def runLazyValsAllowlist: List[String] = loadList(runLazyValsAllowlistFile)
 

compiler/test/dotty/tools/vulpix/ParallelTesting.scala

@@ -610,17 +610,31 @@ trait ParallelTesting extends RunnerOrchestration { self =>
           .run()
           .mkString(JFile.pathSeparator)
 
-      val stdlibClasspath = artifactClasspath("org.scala-lang", "scala3-library_3")
-      val scalacClasspath = artifactClasspath("org.scala-lang", "scala3-compiler_3")
+      val useScala2 = compiler.startsWith("2")
 
-      val pageWidth = TestConfiguration.pageWidth - 20
-      val flags1 = flags.copy(defaultClassPath = stdlibClasspath)
-        .withClasspath(targetDir.getPath)
-        .and("-d", targetDir.getPath)
-        .and("-pagewidth", pageWidth.toString)
+      val stdlibClasspath =
+        val moduleName = if useScala2 then "scala-library" else "scala3-library_3"
+        artifactClasspath("org.scala-lang", moduleName)
+      val scalacClasspath =
+        val moduleName = if useScala2 then "scala-compiler" else "scala3-compiler_3"
+        artifactClasspath("org.scala-lang", moduleName)
 
-      val scalacCommand = Array("java", "-cp", scalacClasspath, "dotty.tools.dotc.Main")
-      val command = scalacCommand ++ flags1.all ++ files.map(_.getAbsolutePath)
+      val pageWidth = TestConfiguration.pageWidth - 20
+      val testArgs =
+        if useScala2 then
+          // We disregard all flags for simplicity to avoid passing unsupported flags to Scala 2.
+          // TODO: support Scala.js with Scala 2 compiler
+          flags.classpath ++ Array("-d", targetDir.getPath)
+        else
+          flags.copy(defaultClassPath = stdlibClasspath)
+            .withClasspath(targetDir.getPath)
+            .and("-d", targetDir.getPath)
+            .and("-pagewidth", pageWidth.toString)
+            .all
+
+      val main = if useScala2 then "scala.tools.nsc.Main" else "dotty.tools.dotc.Main"
+      val scalacCommand = Array("java", "-cp", scalacClasspath, main)
+      val command = scalacCommand ++ testArgs ++ files.map(_.getAbsolutePath)
       val process = Runtime.getRuntime.exec(command)
 
       val reporter = mkReporter

compiler/test/dotty/tools/vulpix/TestFlags.scala

@@ -4,6 +4,8 @@ import scala.language.unsafeNulls
 
 import java.io.{File => JFile}
 
+import dotty.tools.io.File.pathSeparator
+
 final case class TestFlags(
   defaultClassPath: String,
   runClassPath: String, // class path that is used when running `run` tests (not compiling)
@@ -25,7 +27,9 @@ final case class TestFlags(
   def withJavacOnlyOptions(flags: String*): TestFlags =
     TestFlags(defaultClassPath, runClassPath, options, javacOptions ++ flags)
 
-  def all: Array[String] = Array("-classpath", defaultClassPath) ++ options
+  def all: Array[String] = classpath ++ options
+
+  def classpath: Array[String] = Array("-classpath", s"$defaultClassPath$pathSeparator$runClassPath")
 
   def withoutLanguageFeatures: TestFlags = copy(options = withoutLanguageFeaturesOptions)
 

sjs-compiler-tests/test/scala/dotty/tools/dotc/ScalaJSCompilationTests.scala

@@ -59,7 +59,7 @@ class ScalaJSCompilationTests extends ParallelTesting {
   @Test def runScalaJS: Unit = {
     implicit val testGroup: TestGroup = TestGroup("runScalaJS")
     aggregateTests(
-      compileFilesInDir("tests/run", scalaJSOptions),
+      compileFilesInDir("tests/run", scalaJSOptions, FileFilter.exclude(TestSources.runScalaJSBlacklistFileBlacklisted)),
     ).checkRuns()
   }
 }