Leverage Scala and its idioms

Author: som-snytt

compiler/test/dotty/tools/vulpix/ChildJVMMain.java

@@ -0,0 +1,52 @@
+package dotty.tools.vulpix
+
+import java.io.{BufferedReader, File, InputStreamReader}
+import java.net.{URL, URLClassLoader}
+import java.util.ArrayList
+
+object ChildJVMMain:
+  val MessageStart = "##THIS IS THE START FOR ME, HELLO##"
+  val MessageEnd = "##THIS IS THE END FOR ME, GOODBYE##"
+
+  def runMain(dir: String): Unit =
+    def meth =
+      val jcp = System.getProperty("java.class.path")
+      val sep = File.pathSeparator
+      System.setProperty("java.class.path", if jcp == null then dir else dir + sep + jcp)
+
+      val loader =
+        val cp = ArrayList[URL]()
+        val paths = dir.split(sep)
+        for path <- paths do
+          cp.add(File(path).toURI().toURL())
+        val urls = cp.toArray(Array.ofDim[URL](cp.size))
+        URLClassLoader(urls)
+
+      val cls = loader.loadClass("Test")
+      cls.getMethod("main", classOf[Array[String]])
+    end meth
+    val m =
+      try meth
+      catch t =>
+        // Include the failure stack trace to the test output
+        System.out.println(MessageStart)
+        t.printStackTrace()
+        throw t
+    System.out.println(MessageStart);
+    m.invoke(null, null)
+
+  def main(args: Array[String]): Unit =
+    inline def savingSystem[T](inline body: => T): T =
+      val savedIn  = System.in
+      val savedOut = System.out
+      val savedErr = System.err
+      try body
+      finally
+        System.setIn(savedIn)
+        System.setOut(savedOut)
+        System.setErr(savedErr)
+    val stdin = BufferedReader(InputStreamReader(System.in))
+    while true do
+      savingSystem:
+        runMain(stdin.readLine())
+      println(MessageEnd)

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

@@ -1292,21 +1292,19 @@ trait ParallelTesting extends RunnerOrchestration:
       this
     }
 
-    /** Extract `Failure` set and render from `Test` */
-    private def reasonsForFailure(test: Test): String = {
-      val failureReport =
-        if test.failureCount == 0 then ""
-        else s"encountered ${test.failureCount} test failure(s):\n"
-
-      failureReport + test.failureReasons.collect {
-        case test.TimeoutFailure(title) =>
-          s"  - test '$title' timed out"
-        case test.JavaCompilationFailure(msg) =>
-          s"  - java compilation failed with:\n${ msg.linesIterator.map("      " + _).mkString("\n") }"
-        case test.Generic =>
-           "  - generic failure (see test output)"
-      }.mkString("\n")
-    }
+    /** Extracts `Failure` set and renders from `Test`. */
+    private def reasonsForFailure(test: Test): String =
+      if test.failureCount == 0 then ""
+      else
+        test.failureReasons.collect {
+          case test.TimeoutFailure(title) =>
+            s"  - test '$title' timed out"
+          case test.JavaCompilationFailure(msg) =>
+            val header = "  - java compilation failed with:\n"
+            msg.linesIterator.map("      " + _).mkString(header, "\n", "")
+          case test.Generic =>
+             "  - generic failure (see test output)"
+        }.mkString(s"encountered ${test.failureCount} test failure(s):\n", "\n", "")
 
     /** Copies `file` to `dir` - taking into account if `file` is a directory,
      *  and if so copying recursively

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

@@ -98,40 +98,35 @@ trait RunnerOrchestration {
 
       def readLine(): String =
         stdout.readLine() match
-          case s"Listening for transport dt_socket at address: $port" =>
-            throw new IOException(
-              s"Unexpected transport dt_socket message." +
-              " The port is going to be lost and no debugger will be able to connect."
-            )
-          case line => line
+        case s"Listening for transport dt_socket at address: $port" =>
+          throw IOException(
+            "Unexpected transport dt_socket message." +
+            " The port is going to be lost and no debugger will be able to connect."
+          )
+        case line => line
 
       def printLine(line: String): Unit = stdin.println(line)
 
       def getJdiPort(): Int =
         stdout.readLine() match
-          case s"Listening for transport dt_socket at address: $port" => port.toInt
-          case line => throw new IOException(s"Failed getting JDI port of child JVM: got $line")
+        case s"Listening for transport dt_socket at address: $port" => port.toInt
+        case line => throw IOException(s"Failed getting JDI port of child JVM: got $line")
 
-      export p.{exitValue, isAlive, destroy}
+      def isAlive: Boolean = p.isAlive // export p.isAlive sans parens
+
+      export p.{exitValue, destroy}
     end RunnerProcess
 
     private class Runner(private var process: RunnerProcess):
-      /** Checks if `process` is still alive
-       *
-       *  When `process.exitValue()` is called on an active process the caught
-       *  exception is thrown. As such we can know if the subprocess exited or
-       *  not.
-       */
-      def isAlive: Boolean =
-        try { process.exitValue(); false }
-        catch case _: IllegalThreadStateException => true
-
-      /** Destroys the underlying process and kills IO streams */
+      /** Checks whether the underlying process is still alive. */
+      def isAlive: Boolean = process.isAlive
+
+      /** Destroys the underlying process and kills IO streams. */
       def kill(): Unit =
         if (process ne null) process.destroy()
         process = null
 
-      /** Blocks less than `maxDuration` while running `Test.main` from `dir` */
+      /** Blocks less than `maxDuration` while running `Test.main` from `dir`. */
       def runMain(classPath: String): Status =
         assert(process ne null, "Runner was killed and then reused without setting a new process")
         awaitStatusOrRespawn(startMain(classPath))
@@ -172,7 +167,7 @@ trait RunnerOrchestration {
             sb.append(childOutput).append(System.lineSeparator)
             childOutput = process.readLine()
 
-          if process.isAlive() && childOutput != null then Success(sb.toString)
+          if isAlive && childOutput != null then Success(sb.toString)
           else Failure(sb.toString)
       end startMain
 
@@ -198,7 +193,7 @@ trait RunnerOrchestration {
      *  scala library.
      */
     private def createProcess(): RunnerProcess =
-      val url = classOf[ChildJVMMain].getProtectionDomain.getCodeSource.getLocation
+      val url = classOf[ChildJVMMain.type].getProtectionDomain.getCodeSource.getLocation
       val cp = Paths.get(url.toURI).toString + JFile.pathSeparator + Properties.scalaLibrary
       val javaBin = Paths.get(sys.props("java.home"), "bin", "java").toString
       val args = Seq("-Dfile.encoding=UTF-8", "-Duser.language=en", "-Duser.country=US", "-Xmx1g", "-cp", cp) ++

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

@@ -1,5 +1 @@
-object Test {
-  def main(args: Array[String]): Unit = {
-    Thread.sleep(10 * 1000)
-  }
-}
+@main def Test = Thread.sleep(1000 * 1000)