Scala example source code file (BrowsingLoaders.scala)

This example Scala source code file (BrowsingLoaders.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

abstractfile, browsertraverser, browsertraverser, malformedinput, no, outlineparser, sourcefileloader, sourcefileloader, symbol, symbol, symbolloader, tree, tree, unit

The Scala BrowsingLoaders.scala source code

/* NSC -- new Scala compiler
 * Copyright 2005-2011 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala.tools.nsc
package symtab
 
import scala.tools.nsc.io.AbstractFile
import scala.tools.nsc.util.BatchSourceFile

/** A subclass of SymbolLoaders that implements browsing behavior.
 *  This class should be used whenever file dependencies and recompile sets
 *  are managed automoatically.
 */
abstract class BrowsingLoaders extends SymbolLoaders {
  import global._

  import syntaxAnalyzer.{OutlineParser, MalformedInput}

  /** In browse mode, it can happen that an encountered symbol is already
   *  present. For instance, if the source file has a name different from
   *  the classes and objects it contains, the symbol loader will always
   *  reparse the source file. The symbols it encounters might already be loaded
   *  as class files. In this case we return the one which has a sourcefile
   *  (and the other has not), and issue an error if both have sourcefiles.
   */
  override protected def enterIfNew(owner: Symbol, member: Symbol, completer: SymbolLoader): Symbol = {
    completer.sourcefile match {
      case Some(src) => 
        (if (member.isModule) member.moduleClass else member).sourceFile = src
      case _ =>
    }
    val decls = owner.info.decls
    val existing = decls.lookup(member.name)
    if (existing == NoSymbol) {
      decls enter member
      member
    } else if (existing.sourceFile == null) {
      decls unlink existing
      decls enter member
      member
    } else {
      if (member.sourceFile != null) {
        if (existing.sourceFile != member.sourceFile) 
          error(member+"is defined twice,"+
                "\n in "+existing.sourceFile+
                "\n and also in "+member.sourceFile)
      }
      existing
    }
  }

  /** Browse the top-level of given abstract file `src` and enter
   *  eny encountered top-level classes and modules in `root`
   */
  def browseTopLevel(root: Symbol, src: AbstractFile) {  

    class BrowserTraverser extends Traverser {
      var packagePrefix = ""
      var entered = 0
      def addPackagePrefix(pkg: Tree): Unit = pkg match {
        case Select(pre, name) =>
          addPackagePrefix(pre)
          packagePrefix += ("." + name)
        case Ident(name) =>
          if (packagePrefix.length != 0) packagePrefix += "."
          packagePrefix += name
        case _ =>
          throw new MalformedInput(pkg.pos.point, "illegal tree node in package prefix: "+pkg)
      }
      override def traverse(tree: Tree): Unit = tree match {
        case PackageDef(pkg, body) =>
          addPackagePrefix(pkg)
          body foreach traverse
        case ClassDef(_, name, _, _) =>
          if (packagePrefix == root.fullName) {
            enterClass(root, name.toString, new SourcefileLoader(src))
            entered += 1
          } else println("prefixes differ: "+packagePrefix+","+root.fullName)
        case ModuleDef(_, name, _) =>
          if (packagePrefix == root.fullName) {
            val module = enterModule(root, name.toString, new SourcefileLoader(src))
            entered += 1
            if (name == nme.PACKAGEkw) {
              println("open package module: "+module)
              loaders.openPackageModule(module)()
            }
          } else println("prefixes differ: "+packagePrefix+","+root.fullName)
        case _ =>
      }
    }

//    System.out.println("Browsing "+src)
    val source = getSourceFile(src) // this uses the current encoding
    val body = new OutlineParser(source).parse()
//    System.out.println(body)
    val browser = new BrowserTraverser
    browser.traverse(body)
    if (browser.entered == 0) 
      warning("No classes or objects found in "+source+" that go in "+root)
  }

  /** Enter top-level symbols from a source file
   */
  override def enterToplevelsFromSource(root: Symbol, name: String, src: AbstractFile) {
    try {
      if (root == definitions.RootClass || root == definitions.EmptyPackageClass)
        super.enterToplevelsFromSource(root, name, src)
      else 
        browseTopLevel(root, src)
    } catch {
      case ex: syntaxAnalyzer.MalformedInput =>
        println("[%s] caught malformed input exception at offset %d: %s".format(src, ex.offset, ex.msg))
        super.enterToplevelsFromSource(root, name, src)
    }
  }
}