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Scala example source code file (REPL.scala)

This example Scala source code file (REPL.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

array, compiler, consolereporter, list, nsc, position, reflection, repl, response, right, scala, string, u, utilities

The REPL.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2009-2013 Typesafe/Scala Solutions and LAMP/EPFL
 * @author Martin Odersky
 */
package scala
package tools.nsc
package interactive

import scala.reflect.internal.util._
import scala.tools.nsc.reporters._
import scala.tools.nsc.io._
import java.io.FileWriter

/** Interface of interactive compiler to a client such as an IDE
 */
object REPL {

  val versionMsg = "Scala compiler " +
    Properties.versionString + " -- " +
    Properties.copyrightString

  val prompt = "> "

  var reporter: ConsoleReporter = _

  private def replError(msg: String) {
    reporter.error(/*new Position */FakePos("scalac"),
                   msg + "\n  scalac -help  gives more information")
  }

  def process(args: Array[String]) {
    val settings = new Settings(replError)
    reporter = new ConsoleReporter(settings)
    val command = new CompilerCommand(args.toList, settings)
    if (command.settings.version)
      reporter.echo(versionMsg)
    else {
      try {
        object compiler extends Global(command.settings, reporter) {
//          printTypings = true
        }
        if (reporter.hasErrors) {
          reporter.flush()
          return
        }
        if (command.shouldStopWithInfo) {
          reporter.echo(command.getInfoMessage(compiler))
        } else {
          run(compiler)
        }
      } catch {
        case ex @ FatalError(msg) =>
          if (true || command.settings.debug) // !!!
            ex.printStackTrace()
          reporter.error(null, "fatal error: " + msg)
      }
    }
  }

  def main(args: Array[String]) {
    process(args)
    sys.exit(if (reporter.hasErrors) 1 else 0)
  }

  def loop(action: (String) => Unit) {
    Console.print(prompt)
    try {
      val line = Console.readLine()
      if (line.length() > 0) {
        action(line)
      }
      loop(action)
    }
    catch {
      case _: java.io.EOFException => //nop
    }
  }

  /** Commands:
   *
   *  reload file1 ... fileN
   *  typeat file off1 off2?
   *  complete file off1 off2?
   */
  def run(comp: Global) {
    val reloadResult = new Response[Unit]
    val typeatResult = new Response[comp.Tree]
    val completeResult = new Response[List[comp.Member]]
    val typedResult = new Response[comp.Tree]
    val structureResult = new Response[comp.Tree]

    def makePos(file: String, off1: String, off2: String) = {
      val source = toSourceFile(file)
      comp.rangePos(source, off1.toInt, off1.toInt, off2.toInt)
    }

    def doTypeAt(pos: Position) {
      comp.askTypeAt(pos, typeatResult)
      show(typeatResult)
    }

    def doComplete(pos: Position) {
      comp.askTypeCompletion(pos, completeResult)
      show(completeResult)
    }

    def doStructure(file: String) {
      comp.askParsedEntered(toSourceFile(file), keepLoaded = false, structureResult)
      show(structureResult)
    }

    loop { line =>
      (line split " ").toList match {
        case "reload" :: args =>
          comp.askReload(args map toSourceFile, reloadResult)
          show(reloadResult)
        case "reloadAndAskType" :: file :: millis :: Nil =>
          comp.askReload(List(toSourceFile(file)), reloadResult)
          Thread.sleep(millis.toLong)
          println("ask type now")
          comp.askLoadedTyped(toSourceFile(file), keepLoaded = true, typedResult)
          typedResult.get
        case List("typeat", file, off1, off2) =>
          doTypeAt(makePos(file, off1, off2))
        case List("typeat", file, off1) =>
          doTypeAt(makePos(file, off1, off1))
        case List("complete", file, off1, off2) =>
          doComplete(makePos(file, off1, off2))
        case List("complete", file, off1) =>
          doComplete(makePos(file, off1, off1))
        case List("quit") =>
          comp.askShutdown()
          sys.exit(1)
        case List("structure", file) =>
          doStructure(file)
        case _ =>
          print("""Available commands:
                  | reload <file_1> ... <file_n>
                  | reloadAndAskType <file> <sleep-ms>
                  | typed <file>
                  | typeat <file> <start-pos> <end-pos>
                  | typeat <file> <pos>
                  | complete <file> <start-pos> <end-pos>
                  | compile <file> <pos>
                  | structure <file>
                  | quit
                  |""".stripMargin)
      }
    }
  }

  def toSourceFile(name: String) = new BatchSourceFile(new PlainFile(new java.io.File(name)))

  def using[T, U](svar: Response[T])(op: T => U): Option[U] = {
    val res = svar.get match {
      case Left(result) => Some(op(result))
      case Right(exc) => exc.printStackTrace; println("ERROR: "+exc); None
    }
    svar.clear()
    res
  }

  def show[T](svar: Response[T]) = using(svar)(res => println("==> "+res))
}

Other Scala source code examples

Here is a short list of links related to this Scala REPL.scala source code file:

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