Scala example source code file (TreeBrowsers.scala)

This example Scala source code file (TreeBrowsers.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

anyref, boolean, concurrent, document, jtree, list, nil, string, text, tree, unit, unittree

The TreeBrowsers.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala
package tools.nsc
package ast

import java.awt.{List => awtList, _}
import java.awt.event._
import java.io.StringWriter

import javax.swing._
import javax.swing.event.TreeModelListener
import javax.swing.tree._

import scala.concurrent.Lock
import scala.text._
import scala.language.implicitConversions

/**
 * Tree browsers can show the AST in a graphical and interactive
 * way, useful for debugging and understanding.
 *
 * @author Iulian Dragos
 * @version 1.0
 */
abstract class TreeBrowsers {
  val global: Global
  import global._
  import nme.EMPTY

  val borderSize = 10

  def create(): SwingBrowser = new SwingBrowser()

  /** Pseudo tree class, so that all JTree nodes are treated uniformly */
  case class ProgramTree(units: List[UnitTree]) extends Tree {
    override def toString: String = "Program"
  }

  /** Pseudo tree class, so that all JTree nodes are treated uniformly */
  case class UnitTree(unit: CompilationUnit) extends Tree {
    override def toString: String = unit.toString
  }

  /**
   * Java Swing pretty printer for Scala abstract syntax trees.
   */
  class SwingBrowser {
    def browse(pName: String, units: Iterator[CompilationUnit]): Unit =
      browse(pName, units.toList)

    /** print the whole program */
    def browse(pName: String, units: List[CompilationUnit]): Unit = {
      var unitList: List[UnitTree] = Nil

      for (i <- units)
        unitList = UnitTree(i) :: unitList
      val tm = new ASTTreeModel(ProgramTree(unitList))

      val frame = new BrowserFrame(pName)
      frame.setTreeModel(tm)

      val lock = new Lock()
      frame.createFrame(lock)

      // wait for the frame to be closed
      lock.acquire()
    }
  }

  /** Tree model for abstract syntax trees */
  class ASTTreeModel(val program: Tree) extends TreeModel {
    var listeners: List[TreeModelListener] = Nil

    /** Add a listener to this tree */
    def addTreeModelListener(l: TreeModelListener): Unit =
      listeners = l :: listeners

    /** Return the index'th child of parent */
    def getChild(parent: AnyRef, index: Int): AnyRef =
      packChildren(parent)(index)

    /** Return the number of children this 'parent' has */
    def getChildCount(parent: AnyRef): Int =
      packChildren(parent).length

    /** Return the index of the given child */
    def getIndexOfChild(parent: AnyRef, child: AnyRef): Int =
      packChildren(parent) indexOf child

    /** Return the root node */
    def getRoot(): AnyRef = program

    /** Test whether the given node is a leaf */
    def isLeaf(node: AnyRef): Boolean = packChildren(node).isEmpty

    def removeTreeModelListener(l: TreeModelListener): Unit =
      listeners = listeners filterNot (_ == l)

    /** we ignore this message for now */
    def valueForPathChanged(path: TreePath, newValue: AnyRef) = ()

    /**
     * Return a list of children for the given node.
     */
    def packChildren(t: AnyRef): List[AnyRef] = TreeInfo.children(t.asInstanceOf[Tree])
  }




  /**
   * A window that can host the Tree widget and provide methods for
   * displaying information
   *
   * @author Iulian Dragos
   * @version 1.0
   */
  class BrowserFrame(phaseName: String = "unknown") {
    try {
      UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel")
    }
    catch {
      case _: Throwable => UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName())
    }

    val frame = new JFrame("Scala AST after " + phaseName + " phase")
    frame.setJMenuBar(new ASTMenuBar())
    val topLeftPane = new JPanel(new BorderLayout())
    val topRightPane = new JPanel(new BorderLayout())
    val bottomPane = new JPanel(new BorderLayout())
    var splitPane: JSplitPane = _
    var treeModel: ASTTreeModel = _
    var jTree: JTree = _
    val textArea: JTextArea = new JTextArea(30, 120)
    textArea.setBorder(BorderFactory.createEmptyBorder(borderSize, borderSize, borderSize, borderSize))

    val infoPanel = new TextInfoPanel()


    private def setExpansionState(root: JTree, expand: Boolean): Unit = {
      def _setExpansionState(root: JTree, path: TreePath): Unit = {
        val last = path.getLastPathComponent
        for (i <- 0 until root.getModel.getChildCount(last)) {
          val child = root.getModel.getChild(last, i)
          val childPath = path pathByAddingChild child
          _setExpansionState(root, childPath)
        }
        if (expand) {jTree expandPath path}
        else {jTree collapsePath path}
      }
      _setExpansionState(root, new TreePath(root.getModel.getRoot))
    }

    def expandAll(subtree: JTree) = setExpansionState(subtree, expand = true)
    def collapseAll(subtree: JTree) = setExpansionState(subtree, expand = false)


    /** Create a frame that displays the AST.
     *
     * @param lock The lock is used in order to stop the compilation thread
     * until the user is done with the tree inspection. Swing creates its
     * own threads when the frame is packed, and therefore execution
     * would continue. However, this is not what we want, as the tree and
     * especially symbols/types would change while the window is visible.
     */
    def createFrame(lock: Lock): Unit = {
      lock.acquire() // keep the lock until the user closes the window

      frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE)

      frame.addWindowListener(new WindowAdapter() {
        /** Release the lock, so compilation may resume after the window is closed. */
        override def windowClosed(e: WindowEvent): Unit = lock.release()
      })

      jTree = new JTree(treeModel) {
        /** Return the string for a tree node. */
        override def convertValueToText(value: Any, sel: Boolean,
                                        exp: Boolean, leaf: Boolean,
                                        row: Int, hasFocus: Boolean) = {
            val (cls, name) = TreeInfo.treeName(value.asInstanceOf[Tree])
            if (name != EMPTY)
              cls + "[" + name + "]"
            else
              cls
        }
      }

      jTree.addTreeSelectionListener(new javax.swing.event.TreeSelectionListener() {
        def valueChanged(e: javax.swing.event.TreeSelectionEvent): Unit = {
          textArea.setText(e.getPath().getLastPathComponent().toString)
          infoPanel.update(e.getPath().getLastPathComponent())
        }
      })

      val topSplitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, topLeftPane, topRightPane)
      topSplitPane.setResizeWeight(0.5)

      jTree.setBorder(
        BorderFactory.createEmptyBorder(borderSize, borderSize, borderSize, borderSize))
      topLeftPane.add(new JScrollPane(jTree), BorderLayout.CENTER)
      topRightPane.add(new JScrollPane(infoPanel), BorderLayout.CENTER)
      bottomPane.add(new JScrollPane(textArea), BorderLayout.CENTER)
      textArea.setFont(new Font("monospaced", Font.PLAIN, 14))
      textArea.setEditable(false)

      splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, topSplitPane, bottomPane)
      frame.getContentPane().add(splitPane)
      frame.pack()
      frame.setVisible(true)
    }

    class ASTMenuBar extends JMenuBar {
      val menuKey = Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()
      val shiftKey = InputEvent.SHIFT_MASK
      val jmFile = new JMenu("File")
      // val jmiSaveImage = new JMenuItem(
      //   new AbstractAction("Save Tree Image") {
      //     putValue(Action.ACCELERATOR_KEY, KeyStroke.getKeyStroke(KeyEvent.VK_S, menuKey, false))
      //     override def actionPerformed(e: ActionEvent) {
      //       //TODO
      //     }
      //   }
      // )

      // jmFile add jmiSaveImage

      def closeWindow() = frame.getToolkit().getSystemEventQueue().postEvent(
        new WindowEvent(frame, WindowEvent.WINDOW_CLOSING))

      val jmiCancel = new JMenuItem (
        new AbstractAction("Cancel Compilation") {
          putValue(Action.ACCELERATOR_KEY, KeyStroke.getKeyStroke(KeyEvent.VK_Q, menuKey + shiftKey, false))
          override def actionPerformed(e: ActionEvent) {
            closeWindow()
            global.currentRun.cancel()
          }
        }
      )
      jmFile add jmiCancel

      val jmiExit = new JMenuItem (
        new AbstractAction("Exit") {
          putValue(Action.ACCELERATOR_KEY, KeyStroke.getKeyStroke(KeyEvent.VK_Q, menuKey, false))
          override def actionPerformed(e: ActionEvent) = closeWindow()
        }
      )
      jmFile add jmiExit
      add(jmFile)

      val jmView = new JMenu("View")
      val jmiExpand = new JMenuItem(
        new AbstractAction("Expand All Nodes") {
          putValue(Action.ACCELERATOR_KEY, KeyStroke.getKeyStroke(KeyEvent.VK_E, menuKey, false))
          override def actionPerformed(e: ActionEvent) {
            expandAll(jTree)
          }
        }
      )
      jmView add jmiExpand
      val jmiCollapse = new JMenuItem(
        new AbstractAction("Collapse All Nodes") {
          putValue(Action.ACCELERATOR_KEY, KeyStroke.getKeyStroke(KeyEvent.VK_L, menuKey, false))
          override def actionPerformed(e: ActionEvent) {
            collapseAll(jTree)
          }
        }
      )
      jmView add jmiCollapse
      add(jmView)
    }

    def setTreeModel(tm: ASTTreeModel): Unit = treeModel = tm
  }

  /**
   * Present detailed information about the selected tree node.
   */
  class TextInfoPanel extends JTextArea(20, 50) {

    setBorder(BorderFactory.createEmptyBorder(borderSize, borderSize, borderSize, borderSize))
    setEditable(false)
    setFont(new Font("monospaced", Font.PLAIN, 12))

    def update(v: AnyRef): Unit = {
      val t: Tree = v.asInstanceOf[Tree]
      val str = new StringBuilder()
      var buf = new StringWriter()

      t match {
        case ProgramTree(_) => ()
        case UnitTree(_)    => ()
        case _ =>
          str.append("tree.id: ").append(t.id)
          str.append("\ntree.pos: ").append(t.pos)
          str.append("\nSymbol: ").append(TreeInfo.symbolText(t))
          str.append("\nSymbol owner: ").append(
            if ((t.symbol ne null) && t.symbol != NoSymbol)
              t.symbol.owner.toString
            else
              "NoSymbol has no owner")
          if ((t.symbol ne null) && t.symbol.isType) {
            str.append("\ntermSymbol: " + t.symbol.tpe.termSymbol
                     + "\ntypeSymbol: " + t.symbol.tpe.typeSymbol)
          if (t.symbol.isTypeSkolem)
            str.append("\nSkolem of: " + t.symbol.deSkolemize)
          }
          str.append("\nSymbol tpe: ")
          if (t.symbol ne null) {
            str.append(t.symbol.tpe).append("\n")
            buf = new StringWriter()
            TypePrinter.toDocument(t.symbol.tpe).format(getWidth() / getColumnWidth(), buf)
            str.append(buf.toString)
          }
          str.append("\n\nSymbol info: \n")
          TreeInfo.symbolTypeDoc(t).format(getWidth() / getColumnWidth(), buf)
          str.append(buf.toString)
          str.append("\n\nSymbol Attributes: \n").append(TreeInfo.symbolAttributes(t))
          str.append("\ntree.tpe: ")
          if (t.tpe ne null) {
            str.append(t.tpe.toString).append("\n")
            buf = new StringWriter()
            TypePrinter.toDocument(t.tpe).format(getWidth() / getColumnWidth(), buf)
            str.append(buf.toString)
          }
      }
      setText(str.toString)
    }
  }

  /** Computes different information about a tree node. It
   *  is used as central place to do all pattern matching against
   *  Tree.
   */
  object TreeInfo {
    /** Return the case class name and the Name, if the node defines one */
    def treeName(t: Tree): (String, Name) = ((t.productPrefix, t match {
      case UnitTree(unit)                  => newTermName("" + unit)
      case Super(_, mix)                   => newTermName("mix: " + mix)
      case This(qual)                      => qual
      case Select(_, selector)             => selector
      case Ident(name)                     => name
      case SelectFromTypeTree(_, selector) => selector
      case x: DefTree                      => x.name
      case _                               => EMPTY
    }))

    /** Return a list of children for the given tree node */
    def children(t: Tree): List[Tree] = t match {
      case ProgramTree(units) =>
        units

      case UnitTree(unit) =>
        List(unit.body)

      case DocDef(comment, definition) =>
        List(definition)

      case ClassDef(mods, name, tparams, impl) => {
        var children: List[Tree] = List()
        children = tparams ::: children
        mods.annotations ::: impl :: children
      }

      case PackageDef(pid, stats) =>
        stats

      case ModuleDef(mods, name, impl) =>
        mods.annotations ::: List(impl)

      case ValDef(mods, name, tpe, rhs) =>
        mods.annotations ::: List(tpe, rhs)

      case DefDef(mods, name, tparams, vparams, tpe, rhs) =>
        mods.annotations ::: tpe :: rhs :: vparams.flatten ::: tparams

      case TypeDef(mods, name, tparams, rhs) =>
        mods.annotations ::: rhs :: tparams // @M: was List(rhs, lobound)

      case Import(expr, selectors) =>
        List(expr)

      case CaseDef(pat, guard, body) =>
        List(pat, guard, body)

      case Template(parents, self, body) =>
        parents ::: List(self) ::: body

      case LabelDef(name, params, rhs) =>
        params ::: List(rhs)

      case Block(stats, expr) =>
        stats ::: List(expr)

      case Alternative(trees) =>
        trees

      case Bind(name, rhs) =>
        List(rhs)

      case UnApply(fun, args) =>
        fun :: args

      case Match(selector, cases) =>
        selector :: cases

      case Function(vparams, body) =>
        vparams ::: List(body)

      case Assign(lhs, rhs) =>
        List(lhs, rhs)

      case If(cond, thenp, elsep) =>
        List(cond, thenp, elsep)

      case Return(expr) =>
        List(expr)

      case Throw(expr) =>
        List(expr)

      case New(init) =>
        List(init)

      case Typed(expr, tpe) =>
        List(expr, tpe)

      case TypeApply(fun, args) =>
        List(fun) ::: args

      case Apply(fun, args) =>
        List(fun) ::: args

      case ApplyDynamic(qual, args) =>
        List(qual) ::: args

      case Super(qualif, mix) =>
        List(qualif)

      case This(qualif) =>
        Nil

      case Select(qualif, selector) =>
        List(qualif)

      case Ident(name) =>
        Nil

      case Literal(value) =>
        Nil

      case TypeTree() =>
        Nil

      case Annotated(annot, arg) =>
        annot :: List(arg)

      case SingletonTypeTree(ref) =>
        List(ref)

      case SelectFromTypeTree(qualif, selector) =>
        List(qualif)

      case CompoundTypeTree(templ) =>
        List(templ)

      case AppliedTypeTree(tpe, args) =>
        tpe :: args

      case TypeBoundsTree(lo, hi) =>
        List(lo, hi)

      case ExistentialTypeTree(tpt, whereClauses) =>
        tpt :: whereClauses

      case Try(block, catches, finalizer) =>
        block :: catches ::: List(finalizer)

      case ArrayValue(elemtpt, elems) =>
        elemtpt :: elems

      case EmptyTree =>
        Nil

      case Star(t) =>
        List(t)
    }

    /** Return a textual representation of this t's symbol */
    def symbolText(t: Tree): String = {
      val prefix =
        if (t.hasSymbolField)  "[has] "
        else if (t.isDef) "[defines] "
        else ""

      prefix + t.symbol
    }

    /** Return t's symbol type  */
    def symbolTypeDoc(t: Tree): Document = {
      val s = t.symbol
      if (s ne null)
        TypePrinter.toDocument(s.info)
      else
        DocNil
    }

    /** Return a textual representation of (some of) the symbol's
     * attributes */
    def symbolAttributes(t: Tree): String = {
      val s = t.symbol

      if ((s ne null) && (s != NoSymbol)) {
        var str = s.flagString
        if (s.isStaticMember) str = str + " isStatic "
        (str + " annotations: " + s.annotations.mkString("", " ", "")
          + (if (s.isTypeSkolem) "\ndeSkolemized annotations: " + s.deSkolemize.annotations.mkString("", " ", "") else ""))
      }
      else ""
    }
  }

  object TypePrinter {

    ///////////////// Document pretty printer ////////////////

    implicit def view(n: String): Document = DocText(n)

    def toDocument(sym: Symbol): Document =
      toDocument(sym.info)

    def symsToDocument(syms: List[Symbol]): Document = syms match {
      case Nil => DocNil
      case s :: Nil => Document.group(toDocument(s))
      case _ =>
        Document.group(
          syms.tail.foldLeft (toDocument(syms.head) :: ", ") (
            (d: Document, s2: Symbol) => toDocument(s2) :: ", " :/: d) )
    }

    def toDocument(ts: List[Type]): Document = ts match {
      case Nil => DocNil
      case t :: Nil => Document.group(toDocument(t))
      case _ =>
        Document.group(
          ts.tail.foldLeft (toDocument(ts.head) :: ", ") (
            (d: Document, t2: Type) => toDocument(t2) :: ", " :/: d) )
    }

    def toDocument(t: Type): Document = t match {
      case ErrorType => "ErrorType()"
      case WildcardType => "WildcardType()"
      case NoType => "NoType()"
      case NoPrefix => "NoPrefix()"
      case ThisType(s) => "ThisType(" + s.name + ")"

      case SingleType(pre, sym) =>
        Document.group(
          Document.nest(4, "SingleType(" :/:
                      toDocument(pre) :: ", " :/: sym.name.toString :: ")")
        )

      case ConstantType(value) =>
         "ConstantType(" + value + ")"

      case TypeRef(pre, sym, args) =>
        Document.group(
          Document.nest(4, "TypeRef(" :/:
                        toDocument(pre) :: ", " :/:
                        sym.name.toString + sym.idString :: ", " :/:
                        "[ " :: toDocument(args) ::"]" :: ")")
        )

      case TypeBounds(lo, hi) =>
        Document.group(
          Document.nest(4, "TypeBounds(" :/:
                        toDocument(lo) :: ", " :/:
                        toDocument(hi) :: ")")
        )

       case RefinedType(parents, defs) =>
        Document.group(
          Document.nest(4, "RefinedType(" :/:
                        toDocument(parents) :: ")")
        )

      case ClassInfoType(parents, defs, clazz) =>
        Document.group(
          Document.nest(4,"ClassInfoType(" :/:
                        toDocument(parents) :: ", " :/:
                        clazz.name.toString + clazz.idString :: ")")
        )

      case MethodType(params, result) =>
        Document.group(
          Document.nest(4, "MethodType(" :/:
                        Document.group("(" :/:
                                       symsToDocument(params) :/:
                                       "), ") :/:
                        toDocument(result) :: ")")
        )

      case NullaryMethodType(result) =>
        Document.group(
          Document.nest(4,"NullaryMethodType(" :/:
                        toDocument(result) :: ")")
        )

      case PolyType(tparams, result) =>
        Document.group(
          Document.nest(4,"PolyType(" :/:
                        Document.group("(" :/:
                                       symsToDocument(tparams) :/:
                                       "), ") :/:
                        toDocument(result) :: ")")
        )

      case AnnotatedType(annots, tp) =>
        Document.group(
          Document.nest(4, "AnnotatedType(" :/:
                        annots.mkString("[", ",", "]") :/:
                        "," :/: toDocument(tp) :: ")")
        )

      case ExistentialType(tparams, result) =>
        Document.group(
            Document.nest(4, "ExistentialType(" :/:
                Document.group("(" :/: symsToDocument(tparams) :/: "), ") :/:
                toDocument(result) :: ")"))

      case ImportType(expr) =>
        "ImportType(" + expr.toString + ")"


      case SuperType(thistpe, supertpe) =>
        Document.group(
          Document.nest(4, "SuperType(" :/:
                        toDocument(thistpe) :/: ", " :/:
                        toDocument(supertpe) ::")"))
      case _ =>
        sys.error("Unknown case: " + t.toString +", "+ t.getClass)
    }
  }

}