Scala example source code file (CompletionAware.scala)

This example Scala source code file (CompletionAware.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

compiler, completionaware, int, list, nil, none, nsc, option, parsed, string

The CompletionAware.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author Paul Phillips
 */

package scala.tools.nsc
package interpreter

/** An interface for objects which are aware of tab completion and
 *  will supply their own candidates and resolve their own paths.
 */
trait CompletionAware {
  /** The complete list of unqualified Strings to which this
   *  object will complete.
   */
  def completions(verbosity: Int): List[String]

  /** The next completor in the chain.
   */
  def follow(id: String): Option[CompletionAware] = None

  /** A list of useful information regarding a specific uniquely
   *  identified completion.  This is specifically written for the
   *  following situation, but should be useful elsewhere too:
   *
   *    x.y.z.methodName<tab>
   *
   *  If "methodName" is among z's completions, and verbosity > 0
   *  indicating tab has been pressed twice consecutively, then we
   *  call alternativesFor and show a list of overloaded method
   *  signatures.
   */
  def alternativesFor(id: String): List[String] = Nil

  /** Given string 'buf', return a list of all the strings
   *  to which it can complete.  This may involve delegating
   *  to other CompletionAware objects.
   */
  def completionsFor(parsed: Parsed): List[String] = {
    import parsed.{ buffer, verbosity }
    val comps = completions(verbosity) filter (_ startsWith buffer)
    val exact = comps contains buffer

    val results =
      if (parsed.isEmpty) comps
      else if (parsed.isUnqualified && !parsed.isLastDelimiter)
        if (verbosity > 0 && exact) alternativesFor(buffer)
        else comps
      else follow(parsed.bufferHead) map (_ completionsFor parsed.bufferTail) getOrElse Nil

    results.sorted
  }
}