Scala example source code file (PathResolver.scala)

This example Scala source code file (PathResolver.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

calculated, compiler, console, directory, eol, io, nsc, pathresolver, reflection, runtime, scala, settings, some, string, the

The PathResolver.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2006-2013 LAMP/EPFL
 * @author  Paul Phillips
 */

package scala
package tools
package util

import scala.tools.reflect.WrappedProperties.AccessControl
import scala.tools.nsc.{ Settings }
import scala.tools.nsc.util.{ ClassPath, JavaClassPath }
import scala.reflect.io.{ File, Directory, Path, AbstractFile }
import scala.reflect.runtime.ReflectionUtils
import ClassPath.{ JavaContext, DefaultJavaContext, join, split }
import PartialFunction.condOpt
import scala.language.postfixOps

// Loosely based on the draft specification at:
// https://wiki.scala-lang.org/display/SIW/Classpath

object PathResolver {
  // Imports property/environment functions which suppress security exceptions.
  import AccessControl._
  import scala.compat.Platform.EOL

  implicit class MkLines(val t: TraversableOnce[_]) extends AnyVal {
    def mkLines: String = t.mkString("", EOL, EOL)
    def mkLines(header: String, indented: Boolean = false, embraced: Boolean = false): String = {
      val space = "\u0020"
      val sep = if (indented) EOL + space * 2 else EOL
      val (lbrace, rbrace) = if (embraced) (space + "{", EOL + "}") else ("", "")
      t.mkString(header + lbrace + sep, sep, rbrace + EOL)
    }
  }
  implicit class AsLines(val s: String) extends AnyVal {
    // sm"""...""" could do this in one pass
    def asLines = s.trim.stripMargin.lines.mkLines
  }

  /** pretty print class path */
  def ppcp(s: String) = split(s) match {
    case Nil      => ""
    case Seq(x)   => x
    case xs       => xs.mkString(EOL, EOL, "")
  }

  /** Values found solely by inspecting environment or property variables.
   */
  object Environment {
    private def searchForBootClasspath = (
      systemProperties find (_._1 endsWith ".boot.class.path") map (_._2) getOrElse ""
    )

    /** Environment variables which java pays attention to so it
     *  seems we do as well.
     */
    def sourcePathEnv       = envOrElse("SOURCEPATH", "")

    def javaBootClassPath   = propOrElse("sun.boot.class.path", searchForBootClasspath)
    def javaExtDirs         = propOrEmpty("java.ext.dirs")
    def scalaHome           = propOrEmpty("scala.home")
    def scalaExtDirs        = propOrEmpty("scala.ext.dirs")

    /** The java classpath and whether to use it. */
    def javaUserClassPath   = propOrElse("java.class.path", "")
    def useJavaClassPath    = propOrFalse("scala.usejavacp")

    override def toString = s"""
      |object Environment {
      |  scalaHome          = $scalaHome (useJavaClassPath = $useJavaClassPath)
      |  javaBootClassPath  = <${javaBootClassPath.length} chars>
      |  javaExtDirs        = ${ppcp(javaExtDirs)}
      |  javaUserClassPath  = ${ppcp(javaUserClassPath)}
      |  scalaExtDirs       = ${ppcp(scalaExtDirs)}
      |}""".asLines
  }

  /** Default values based on those in Environment as interpreted according
   *  to the path resolution specification.
   */
  object Defaults {
    def scalaSourcePath   = Environment.sourcePathEnv
    def javaBootClassPath = Environment.javaBootClassPath
    def javaUserClassPath = Environment.javaUserClassPath
    def javaExtDirs       = Environment.javaExtDirs
    def useJavaClassPath  = Environment.useJavaClassPath

    def scalaHome         = Environment.scalaHome
    def scalaHomeDir      = Directory(scalaHome)
    def scalaLibDir       = Directory(scalaHomeDir / "lib")
    def scalaClassesDir   = Directory(scalaHomeDir / "classes")

    def scalaLibAsJar     = File(scalaLibDir / "scala-library.jar")
    def scalaLibAsDir     = Directory(scalaClassesDir / "library")

    def scalaLibDirFound: Option[Directory] =
      if (scalaLibAsJar.isFile) Some(scalaLibDir)
      else if (scalaLibAsDir.isDirectory) Some(scalaClassesDir)
      else None

    def scalaLibFound =
      if (scalaLibAsJar.isFile) scalaLibAsJar.path
      else if (scalaLibAsDir.isDirectory) scalaLibAsDir.path
      else ""

    // XXX It must be time for someone to figure out what all these things
    // are intended to do.  This is disabled here because it was causing all
    // the scala jars to end up on the classpath twice: one on the boot
    // classpath as set up by the runner (or regular classpath under -nobootcp)
    // and then again here.
    def scalaBootClassPath  = ""
    def scalaExtDirs = Environment.scalaExtDirs
    def scalaPluginPath = (scalaHomeDir / "misc" / "scala-devel" / "plugins").path

    override def toString = s"""
      |object Defaults {
      |  scalaHome            = $scalaHome
      |  javaBootClassPath    = ${ppcp(javaBootClassPath)}
      |  scalaLibDirFound     = $scalaLibDirFound
      |  scalaLibFound        = $scalaLibFound
      |  scalaBootClassPath   = ${ppcp(scalaBootClassPath)}
      |  scalaPluginPath      = ${ppcp(scalaPluginPath)}
      |}""".asLines
  }

  /** Locations discovered by supplemental heuristics.
   */
  object SupplementalLocations {

    /** The platform-specific support jar.
     *
     *  Usually this is `tools.jar` in the jdk/lib directory of the platform distribution.
     *
     *  The file location is determined by probing the lib directory under JDK_HOME or JAVA_HOME,
     *  if one of those environment variables is set, then the lib directory under java.home,
     *  and finally the lib directory under the parent of java.home. Or, as a last resort,
     *  search deeply under those locations (except for the parent of java.home, on the notion
     *  that if this is not a canonical installation, then that search would have little
     *  chance of succeeding).
     */
    def platformTools: Option[File] = {
      val jarName = "tools.jar"
      def jarPath(path: Path) = (path / "lib" / jarName).toFile
      def jarAt(path: Path) = {
        val f = jarPath(path)
        if (f.isFile) Some(f) else None
      }
      val jdkDir = {
        val d = Directory(jdkHome)
        if (d.isDirectory) Some(d) else None
      }
      def deeply(dir: Directory) = dir.deepFiles find (_.name == jarName)

      val home    = envOrSome("JDK_HOME", envOrNone("JAVA_HOME")) map (p => Path(p))
      val install = Some(Path(javaHome))

      (home flatMap jarAt) orElse (install flatMap jarAt) orElse (install map (_.parent) flatMap jarAt) orElse
        (jdkDir flatMap deeply)
    }
    override def toString = s"""
      |object SupplementalLocations {
      |  platformTools        = $platformTools
      |}""".asLines
  }

  // used in PathResolver constructor
  private object NoImplClassJavaContext extends JavaContext {
    override def isValidName(name: String): Boolean =
      !ReflectionUtils.scalacShouldntLoadClassfile(name)
  }

  // called from scalap
  def fromPathString(path: String, context: JavaContext = DefaultJavaContext): JavaClassPath = {
    val s = new Settings()
    s.classpath.value = path
    new PathResolver(s, context) result
  }

  /** With no arguments, show the interesting values in Environment and Defaults.
   *  If there are arguments, show those in Calculated as if those options had been
   *  given to a scala runner.
   */
  def main(args: Array[String]): Unit = {
    if (args.isEmpty) {
      println(Environment)
      println(Defaults)
    }
    else {
      val settings = new Settings()
      val rest = settings.processArguments(args.toList, processAll = false)._2
      val pr = new PathResolver(settings)
      println(" COMMAND: 'scala %s'".format(args.mkString(" ")))
      println("RESIDUAL: 'scala %s'\n".format(rest.mkString(" ")))
      pr.result.show()
    }
  }
}

class PathResolver(settings: Settings, context: JavaContext) {
  import PathResolver.{ Defaults, Environment, AsLines, MkLines, ppcp }

  def this(settings: Settings) = this(settings,
      if (settings.YnoLoadImplClass) PathResolver.NoImplClassJavaContext
      else DefaultJavaContext)

  private def cmdLineOrElse(name: String, alt: String) = {
    (commandLineFor(name) match {
      case Some("") => None
      case x        => x
    }) getOrElse alt
  }

  private def commandLineFor(s: String): Option[String] = condOpt(s) {
    case "javabootclasspath"  => settings.javabootclasspath.value
    case "javaextdirs"        => settings.javaextdirs.value
    case "bootclasspath"      => settings.bootclasspath.value
    case "extdirs"            => settings.extdirs.value
    case "classpath" | "cp"   => settings.classpath.value
    case "sourcepath"         => settings.sourcepath.value
  }

  /** Calculated values based on any given command line options, falling back on
   *  those in Defaults.
   */
  object Calculated {
    def scalaHome           = Defaults.scalaHome
    def useJavaClassPath    = settings.usejavacp.value || Defaults.useJavaClassPath
    def useManifestClassPath= settings.usemanifestcp.value
    def javaBootClassPath   = cmdLineOrElse("javabootclasspath", Defaults.javaBootClassPath)
    def javaExtDirs         = cmdLineOrElse("javaextdirs", Defaults.javaExtDirs)
    def javaUserClassPath   = if (useJavaClassPath) Defaults.javaUserClassPath else ""
    def scalaBootClassPath  = cmdLineOrElse("bootclasspath", Defaults.scalaBootClassPath)
    def scalaExtDirs        = cmdLineOrElse("extdirs", Defaults.scalaExtDirs)
    /** Scaladoc doesn't need any bootstrapping, otherwise will create errors such as:
     * [scaladoc] ../scala-trunk/src/reflect/scala/reflect/macros/Reifiers.scala:89: error: object api is not a member of package reflect
     * [scaladoc] case class ReificationException(val pos: reflect.api.PositionApi, val msg: String) extends Throwable(msg)
     * [scaladoc]                                              ^
     * because the bootstrapping will look at the sourcepath and create package "reflect" in "<root>"
     * and then when typing relative names, instead of picking <root>.scala.relect, typedIdentifier will pick up the
     * <root>.reflect package created by the bootstrapping. Thus, no bootstrapping for scaladoc!
     * TODO: we should refactor this as a separate -bootstrap option to have a clean implementation, no? */
    def sourcePath          = if (!settings.isScaladoc) cmdLineOrElse("sourcepath", Defaults.scalaSourcePath) else ""

    /** Against my better judgment, giving in to martin here and allowing
     *  CLASSPATH to be used automatically.  So for the user-specified part
     *  of the classpath:
     *
     *  - If -classpath or -cp is given, it is that
     *  - Otherwise, if CLASSPATH is set, it is that
     *  - If neither of those, then "." is used.
     */
    def userClassPath = (
      if (!settings.classpath.isDefault)
        settings.classpath.value
      else sys.env.getOrElse("CLASSPATH", ".")
    )

    import context._

    // Assemble the elements!
    def basis = List[Traversable[ClassPath[AbstractFile]]](
      classesInPath(javaBootClassPath),             // 1. The Java bootstrap class path.
      contentsOfDirsInPath(javaExtDirs),            // 2. The Java extension class path.
      classesInExpandedPath(javaUserClassPath),     // 3. The Java application class path.
      classesInPath(scalaBootClassPath),            // 4. The Scala boot class path.
      contentsOfDirsInPath(scalaExtDirs),           // 5. The Scala extension class path.
      classesInExpandedPath(userClassPath),         // 6. The Scala application class path.
      classesInManifest(useManifestClassPath),      // 8. The Manifest class path.
      sourcesInPath(sourcePath)                     // 7. The Scala source path.
    )

    lazy val containers = basis.flatten.distinct

    override def toString = s"""
      |object Calculated {
      |  scalaHome            = $scalaHome
      |  javaBootClassPath    = ${ppcp(javaBootClassPath)}
      |  javaExtDirs          = ${ppcp(javaExtDirs)}
      |  javaUserClassPath    = ${ppcp(javaUserClassPath)}
      |    useJavaClassPath   = $useJavaClassPath
      |  scalaBootClassPath   = ${ppcp(scalaBootClassPath)}
      |  scalaExtDirs         = ${ppcp(scalaExtDirs)}
      |  userClassPath        = ${ppcp(userClassPath)}
      |  sourcePath           = ${ppcp(sourcePath)}
      |}""".asLines
  }

  def containers = Calculated.containers

  lazy val result = {
    val cp = new JavaClassPath(containers.toIndexedSeq, context)
    if (settings.Ylogcp) {
      Console print f"Classpath built from ${settings.toConciseString} %n"
      Console print s"Defaults: ${PathResolver.Defaults}"
      Console print s"Calculated: $Calculated"

      val xs = (Calculated.basis drop 2).flatten.distinct
      Console print (xs mkLines (s"After java boot/extdirs classpath has ${xs.size} entries:", indented = true))
    }
    cp
  }

  def asURLs = result.asURLs
}