Scala example source code file (JLineReader.scala)

This example Scala source code file (JLineReader.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

argumentcompleter, candidates, compiler, completer, history, int, jlineconsolereader, jlinehistory, nohistory, nsc, string, unit

The JLineReader.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author Stepan Koltsov
 */

package scala.tools.nsc
package interpreter

import jline.console.ConsoleReader
import jline.console.completer._
import session._
import Completion._

/**
 *  Reads from the console using JLine.
 */
class JLineReader(_completion: => Completion) extends InteractiveReader {
  val interactive = true
  val consoleReader = new JLineConsoleReader()

  lazy val completion = _completion
  lazy val history: JLineHistory = JLineHistory()

  private def term = consoleReader.getTerminal()
  def reset() = term.reset()

  def scalaToJline(tc: ScalaCompleter): Completer = new Completer {
    def complete(_buf: String, cursor: Int, candidates: JList[CharSequence]): Int = {
      val buf   = if (_buf == null) "" else _buf
      val Candidates(newCursor, newCandidates) = tc.complete(buf, cursor)
      newCandidates foreach (candidates add _)
      newCursor
    }
  }

  class JLineConsoleReader extends ConsoleReader with ConsoleReaderHelper with VariColumnTabulator {
    val isAcross = interpreter.`package`.isAcross

    this setPaginationEnabled interpreter.`package`.isPaged

    // ASAP
    this setExpandEvents false

    // working around protected/trait/java insufficiencies.
    def goBack(num: Int): Unit = back(num)
    if ((history: History) ne NoHistory)
      this setHistory history

    def readOneKey(prompt: String) = {
      this.print(prompt)
      this.flush()
      this.readCharacter()
    }
    def eraseLine() = consoleReader.resetPromptLine("", "", 0)
    def redrawLineAndFlush(): Unit = { flush() ; drawLine() ; flush() }

    // A hook for running code after the repl is done initializing.
    lazy val postInit: Unit = {
      this setBellEnabled false

      if (completion ne NoCompletion) {
        val argCompletor: ArgumentCompleter =
          new ArgumentCompleter(new JLineDelimiter, scalaToJline(completion.completer()))
        argCompletor setStrict false

        this addCompleter argCompletor
        this setAutoprintThreshold 400 // max completion candidates without warning
      }
    }
  }

  def redrawLine() = consoleReader.redrawLineAndFlush()
  def readOneLine(prompt: String) = consoleReader readLine prompt
  def readOneKey(prompt: String)  = consoleReader readOneKey prompt
}