Scala example source code file (ScriptRunner.scala)

This example Scala source code file (ScriptRunner.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

boolean, compiler, file, genericrunnersettings, left, list, none, nsc, scriptrunner, settings, some, string

The ScriptRunner.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala
package tools.nsc

import io.{ Directory, File, Path }
import java.io.IOException
import scala.tools.nsc.reporters.{Reporter,ConsoleReporter}
import util.Exceptional.unwrap

/** An object that runs Scala code in script files.
 *
 *  <p>For example, here is a complete Scala script on Unix:</pre>
 *  <pre>
 *    #!/bin/sh
 *    exec scala "$0" "$@"
 *    !#
 *    Console.println("Hello, world!")
 *    args.toList foreach Console.println
 *  </pre>
 *  <p>And here is a batch file example on Windows XP:</p>
 *  <pre>
 *    ::#!
 *    @echo off
 *    call scala %0 %*
 *    goto :eof
 *    ::!#
 *    Console.println("Hello, world!")
 *    args.toList foreach Console.println
 *  </pre>
 *
 *  @author  Lex Spoon
 *  @version 1.0, 15/05/2006
 *  @todo    It would be better if error output went to stderr instead
 *           of stdout...
 */
class ScriptRunner extends HasCompileSocket {
  lazy val compileSocket = CompileSocket

  /** Default name to use for the wrapped script */
  val defaultScriptMain = "Main"

  /** Pick a main object name from the specified settings */
  def scriptMain(settings: Settings) = settings.script.value match {
    case "" => defaultScriptMain
    case x  => x
  }

  /** Choose a jar filename to hold the compiled version of a script. */
  private def jarFileFor(scriptFile: String)= File(
    if (scriptFile endsWith ".jar") scriptFile
    else scriptFile.stripSuffix(".scala") + ".jar"
  )

  /** Compile a script using the fsc compilation daemon.
   */
  private def compileWithDaemon(settings: GenericRunnerSettings, scriptFileIn: String) = {
    val scriptFile       = Path(scriptFileIn).toAbsolute.path
    val compSettingNames = new Settings(sys.error).visibleSettings.toList map (_.name)
    val compSettings     = settings.visibleSettings.toList filter (compSettingNames contains _.name)
    val coreCompArgs     = compSettings flatMap (_.unparse)
    val compArgs         = coreCompArgs ++ List("-Xscript", scriptMain(settings), scriptFile)

    CompileSocket getOrCreateSocket "" match {
      case Some(sock) => compileOnServer(sock, compArgs)
      case _          => false
    }
  }

  protected def newGlobal(settings: Settings, reporter: Reporter) =
    Global(settings, reporter)

  /** Compile a script and then run the specified closure with
    * a classpath for the compiled script.
    *
    * @return true if compilation and the handler succeeds, false otherwise.
    */
  private def withCompiledScript(
    settings: GenericRunnerSettings,
    scriptFile: String)
    (handler: String => Boolean): Boolean =
  {
    def mainClass = scriptMain(settings)

    /* Compiles the script file, and returns the directory with the compiled
     * class files, if the compilation succeeded.
     */
    def compile: Option[Directory] = {
      val compiledPath = Directory makeTemp "scalascript"

      // delete the directory after the user code has finished
      sys.addShutdownHook(compiledPath.deleteRecursively())

      settings.outdir.value = compiledPath.path

      if (settings.nc) {
        /* Setting settings.script.value informs the compiler this is not a
         * self contained compilation unit.
         */
        settings.script.value = mainClass
        val reporter = new ConsoleReporter(settings)
        val compiler = newGlobal(settings, reporter)

        new compiler.Run compile List(scriptFile)
        if (reporter.hasErrors) None else Some(compiledPath)
      }
      else if (compileWithDaemon(settings, scriptFile)) Some(compiledPath)
      else None
    }

    /* The script runner calls sys.exit to communicate a return value, but this must
     * not take place until there are no non-daemon threads running.  Tickets #1955, #2006.
     */
    util.waitingForThreads {
      if (settings.save) {
        val jarFile = jarFileFor(scriptFile)
        def jarOK   = jarFile.canRead && (jarFile isFresher File(scriptFile))

        def recompile() = {
          jarFile.delete()

          compile match {
            case Some(compiledPath) =>
              try io.Jar.create(jarFile, compiledPath, mainClass)
              catch { case _: Exception => jarFile.delete() }

              if (jarOK) {
                compiledPath.deleteRecursively()
                handler(jarFile.toAbsolute.path)
              }
              // jar failed; run directly from the class files
              else handler(compiledPath.path)
            case _  => false
          }
        }

        if (jarOK) handler(jarFile.toAbsolute.path) // pre-compiled jar is current
        else recompile()                            // jar old - recompile the script.
      }
      // don't use a cache jar at all--just use the class files
      else compile exists (cp => handler(cp.path))
    }
  }

  /** Run a script after it has been compiled
   *
   * @return true if execution succeeded, false otherwise
   */
  private def runCompiled(
    settings: GenericRunnerSettings,
    compiledLocation: String,
    scriptArgs: List[String]): Boolean =
  {
    val cp = File(compiledLocation).toURL +: settings.classpathURLs
    ObjectRunner.runAndCatch(cp, scriptMain(settings), scriptArgs) match {
      case Left(ex) => ex.printStackTrace() ; false
      case _        => true
    }
  }

  /** Run a script file with the specified arguments and compilation
   *  settings.
   *
   * @return true if compilation and execution succeeded, false otherwise.
   */
  def runScript(
    settings: GenericRunnerSettings,
    scriptFile: String,
    scriptArgs: List[String]): Boolean =
  {
    if (File(scriptFile).isFile)
      withCompiledScript(settings, scriptFile) { runCompiled(settings, _, scriptArgs) }
    else
      throw new IOException("no such file: " + scriptFile)
  }

  /** Calls runScript and catches the enumerated exceptions, routing
   *  them to Left(ex) if thrown.
   */
  def runScriptAndCatch(
    settings: GenericRunnerSettings,
    scriptFile: String,
    scriptArgs: List[String]): Either[Throwable, Boolean] =
  {
    try Right(runScript(settings, scriptFile, scriptArgs))
    catch { case e: Throwable => Left(unwrap(e)) }
  }

  /** Run a command
   *
   * @return true if compilation and execution succeeded, false otherwise.
   */
  def runCommand(
    settings: GenericRunnerSettings,
    command: String,
    scriptArgs: List[String]): Boolean =
  {
    val scriptFile = File.makeTemp("scalacmd", ".scala")
    // save the command to the file
    scriptFile writeAll command

    try withCompiledScript(settings, scriptFile.path) { runCompiled(settings, _, scriptArgs) }
    finally scriptFile.delete()  // in case there was a compilation error
  }
}

object ScriptRunner extends ScriptRunner { }