Scala example source code file (AbsSettings.scala)

This example Scala source code file (AbsSettings.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

abssetting, abssettings, compiler, list, nil, nsc, option, setting, settings, string, t, y

The AbsSettings.scala Scala example source code

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

package scala.tools.nsc
package settings

/** A Settings abstraction boiled out of the original highly mutable Settings
 *  class with the intention of creating an ImmutableSettings which can be used
 *  interchangeably.   Except of course without the mutants.
 */

trait AbsSettings extends scala.reflect.internal.settings.AbsSettings {
  type Setting <: AbsSetting      // Fix to the concrete Setting type
  type ResultOfTryToSet           // List[String] in mutable, (Settings, List[String]) in immutable
  def errorFn: String => Unit
  protected def allSettings: scala.collection.Set[Setting]

  // settings minus internal usage settings
  def visibleSettings = allSettings filterNot (_.isInternalOnly)

  // only settings which differ from default
  def userSetSettings = visibleSettings filterNot (_.isDefault)

  // an argument list which (should) be usable to recreate the Settings
  def recreateArgs = userSetSettings.toList flatMap (_.unparse)

  // checks both name and any available abbreviations
  def lookupSetting(cmd: String): Option[Setting] = allSettings find (_ respondsTo cmd)

  // two AbsSettings objects are equal if their visible settings are equal.
  override def hashCode() = visibleSettings.size  // going for cheap
  override def equals(that: Any) = that match {
    case s: AbsSettings => this.userSetSettings == s.userSetSettings
    case _              => false
  }
  override def toString() = "Settings {\n%s}\n" format (userSetSettings map ("  " + _ + "\n")).mkString
  def toConciseString = userSetSettings.mkString("(", " ", ")")

  def checkDependencies =
    visibleSettings filterNot (_.isDefault) forall (setting => setting.dependencies forall {
      case (dep, value) =>
        (Option(dep.value) exists (_.toString == value)) || {
          errorFn("incomplete option %s (requires %s)".format(setting.name, dep.name))
          false
        }
    })

  trait AbsSetting extends Ordered[Setting] with AbsSettingValue {
    def name: String
    def helpDescription: String
    def unparse: List[String]     // A list of Strings which can recreate this setting.

    /* For tools which need to populate lists of available choices */
    def choices : List[String] = Nil

    /** In mutable Settings, these return the same object with a var set.
     *  In immutable, of course they will return a new object, which means
     *  we can't use "this.type", at least not in a non-casty manner, which
     *  is unfortunate because we lose type information without it.
     *
     *  ...but now they're this.type because of #3462.  The immutable
     *  side doesn't exist yet anyway.
     */
    def withAbbreviation(name: String): this.type
    def withHelpSyntax(help: String): this.type
    def withDeprecationMessage(msg: String): this.type

    def helpSyntax: String = name
    def deprecationMessage: Option[String] = None
    def abbreviations: List[String] = Nil
    def dependencies: List[(Setting, String)] = Nil
    def respondsTo(label: String) = (name == label) || (abbreviations contains label)

    /** If the setting should not appear in help output, etc. */
    private var internalSetting = false
    def isInternalOnly = internalSetting
    def internalOnly(): this.type = {
      internalSetting = true
      this
    }

    /** Issue error and return */
    def errorAndValue[T](msg: String, x: T): T = { errorFn(msg) ; x }

    /** After correct Setting has been selected, tryToSet is called with the
     *  remainder of the command line.  It consumes any applicable arguments and
     *  returns the unconsumed ones.
     */
    protected[nsc] def tryToSet(args: List[String]): Option[ResultOfTryToSet]

    /** Commands which can take lists of arguments in form -Xfoo:bar,baz override
     *  this method and accept them as a list.  It returns List[String] for
     *  consistency with tryToSet, and should return its incoming arguments
     *  unmodified on failure, and Nil on success.
     */
    protected[nsc] def tryToSetColon(args: List[String]): Option[ResultOfTryToSet] =
      errorAndValue("'%s' does not accept multiple arguments" format name, None)

    /** Attempt to set from a properties file style property value.
     *  Currently used by Eclipse SDT only.
     *  !!! Needs test.
     */
    def tryToSetFromPropertyValue(s: String): Unit = tryToSet(s :: Nil)

    /** These categorizations are so the help output shows -X and -P among
     *  the standard options and -Y among the advanced options.
     */
    def isAdvanced   = name match { case "-Y" => true ; case "-X" => false ; case _  => name startsWith "-X" }
    def isPrivate    = name match { case "-Y" => false ; case _  => name startsWith "-Y" }
    def isStandard   = !isAdvanced && !isPrivate
    def isForDebug   = name endsWith "-debug" // by convention, i.e. -Ytyper-debug
    def isDeprecated = deprecationMessage.isDefined

    def compare(that: Setting): Int = name compare that.name

    /** Equality tries to sidestep all the drama and define it simply and
     *  in one place: two AbsSetting objects are equal if their names and
     *  values compare equal.
     */
    override def equals(that: Any) = that match {
      case x: AbsSettings#AbsSetting  => (name == x.name) && (value == x.value)
      case _                          => false
    }
    override def hashCode() = name.hashCode + value.hashCode
    override def toString() = name + " = " + (if (value == "") "\"\"" else value)
  }

  trait InternalSetting extends AbsSetting {
    override def isInternalOnly = true
  }
}