Scala example source code file (NodePrinters.scala)

This example Scala source code file (NodePrinters.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, emptytree, list, literal, memberdef, name, nil, nsc, string, super, tree, typetree

The NodePrinters.scala Scala example source code

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

package scala.tools.nsc
package ast

import scala.compat.Platform.EOL
import symtab.Flags._
import scala.language.postfixOps

/** The object `nodePrinter` converts the internal tree
 *  representation to a string.
 *
 *  @author  Stephane Micheloud
 *  @author  Paul Phillips
 */
abstract class NodePrinters {
  val global: Global
  import global._

  object InfoLevel extends Enumeration {
    val Quiet, Normal, Verbose = Value
  }
  var infolevel = InfoLevel.Quiet

  def nodeToString: Tree => String = nodeToRegularString

  object nodeToRegularString extends DefaultPrintAST with (Tree => String) {
    def apply(tree: Tree) = stringify(tree)
  }

  trait DefaultPrintAST extends PrintAST {
    val printPos = settings.Xprintpos || settings.Yposdebug

    def showNameAndPos(tree: NameTree) = showPosition(tree) + showName(tree.name)
    def showDefTreeName(tree: DefTree) = showName(tree.name)
    def showPosition(tree: Tree)       = if (printPos) tree.pos.show else ""
    def showFlags(tree: MemberDef)     = flagsToString(tree.symbol.flags | tree.mods.flags)
    def showLiteral(lit: Literal)      = showPosition(lit) + lit.value.escapedStringValue
    def showTypeTree(tt: TypeTree)     = showPosition(tt) + "<tpt>" + emptyOrComment(showType(tt))
    def showName(name: Name)           = name match {
      case nme.EMPTY | tpnme.EMPTY => "<empty>"
      case name                    => "\"" + name + "\""
    }

    def showSymbol(tree: Tree): String = {
      val sym = tree.symbol
      if (sym == null || sym == NoSymbol) ""
      else sym.defString + sym.locationString
    }
    def showType(tree: Tree): String = {
      val tpe = tree.tpe
      if (tpe == null || tpe == NoType) ""
      else "tree.tpe=" + tpe
    }

    def showAttributes(tree: Tree): String = {
      if (infolevel == InfoLevel.Quiet) ""
      else {
        try   { List(showSymbol(tree), showType(tree)) filterNot (_ == "") mkString ", " trim }
        catch { case ex: Throwable => "sym= <error> " + ex.getMessage }
      }
    }
  }

  trait PrintAST {
    private val buf = new StringBuilder
    private var level = 0

    def showName(name: Name): String
    def showPosition(tree: Tree): String
    def showNameAndPos(tree: NameTree): String
    def showDefTreeName(defTree: DefTree): String
    def showFlags(tree: MemberDef): String
    def showLiteral(lit: Literal): String
    def showTypeTree(tt: TypeTree): String
    def showAttributes(tree: Tree): String  // symbol and type

    def showRefTreeName(tree: Tree): String = {
      tree match {
        case SelectFromTypeTree(qual, name) => showRefTreeName(qual) + "#" + showName(name)
        case Select(qual, name)             => showRefTreeName(qual) + "." + showName(name)
        case id @ Ident(name)               => showNameAndPos(id)
        case _                              => "" + tree
      }
    }
    def showRefTree(tree: RefTree): String = {
      def prefix0 = showRefTreeName(tree.qualifier)
      def prefix = if (prefix0 == "") "" else (tree match {
        case SelectFromTypeTree(_, _) => prefix0 + "#"
        case Select(_, _)             => prefix0 + "."
        case _                        => ""
      })
      prefix + showNameAndPos(tree) + emptyOrComment(showAttributes(tree))
    }

    def emptyOrComment(s: String) = if (s == "") "" else " // " + s

    def stringify(tree: Tree): String = {
      buf.clear()
      if (settings.XshowtreesStringified) buf.append(tree.toString + EOL)
      if (settings.XshowtreesCompact) {
        buf.append(showRaw(tree, printIds = settings.uniqid, printTypes = settings.printtypes))
      } else {
        level = 0
        traverse(tree)
      }
      buf.toString
    }
    def traverseAny(x: Any) {
      x match {
        case t: Tree      => traverse(t)
        case xs: List[_]  => printMultiline("List", "")(xs foreach traverseAny)
        case _            => println("" + x)
      }
    }
    def println(s: String) = printLine(s, "")

    def printLine(value: String, comment: String) {
      buf append "  " * level
      buf append value
      if (comment != "") {
        if (value != "")
          buf append " "

        buf append "// "
        buf append comment
      }
      buf append EOL
    }

    def annotationInfoToString(annot: AnnotationInfo): String = {
      val str = new StringBuilder
      str.append(annot.atp.toString())
      if (!annot.args.isEmpty)
        str.append(annot.args.mkString("(", ",", ")"))
      if (!annot.assocs.isEmpty)
        for (((name, value), index) <- annot.assocs.zipWithIndex) {
          if (index > 0)
            str.append(", ")
          str.append(name).append(" = ").append(value)
        }
      str.toString
    }
    def printModifiers(tree: MemberDef) {
      // SI-5885: by default this won't print annotations of not yet initialized symbols
      val annots0 = tree.symbol.annotations match {
        case Nil  => tree.mods.annotations
        case xs   => xs map annotationInfoToString
      }
      val annots = annots0 match {
        case Nil  => ""
        case xs   => " " + xs.mkString("@{ ", ", ", " }")
      }
      val flagString = showFlags(tree) match {
        case ""   => "0"
        case s    => s
      }
      println(flagString + annots)
    }

    def applyCommon(tree: Tree, fun: Tree, args: List[Tree]) {
      printMultiline(tree) {
        traverse(fun)
        traverseList("Nil", "argument")(args)
      }
    }

    def typeApplyCommon(tree: Tree, fun: Tree, args: List[Tree]) {
      printMultiline(tree) {
        traverse(fun)
        traverseList("[]", "type argument")(args)
      }
    }

    def treePrefix(tree: Tree) = showPosition(tree) + tree.productPrefix
    def printMultiline(tree: Tree)(body: => Unit) {
      printMultiline(treePrefix(tree), showAttributes(tree))(body)
    }
    def printMultiline(prefix: String, comment: String)(body: => Unit) {
      printLine(prefix + "(", comment)
      indent(body)
      println(")")
    }

    @inline private def indent[T](body: => T): T = {
      level += 1
      try body
      finally level -= 1
    }

    def traverseList(ifEmpty: String, what: String)(trees: List[Tree]) {
      if (trees.isEmpty)
        println(ifEmpty)
      else if (trees.tail.isEmpty)
        traverse(trees.head)
      else {
        printLine("", trees.length + " " + what + "s")
        trees foreach traverse
      }
    }

    def printSingle(tree: Tree, name: Name) {
      println(treePrefix(tree) + "(" + showName(name) + ")" + showAttributes(tree))
    }

    def traverse(tree: Tree) {
      showPosition(tree)

      tree match {
        case ApplyDynamic(fun, args)      => applyCommon(tree, fun, args)
        case Apply(fun, args)             => applyCommon(tree, fun, args)

        case TypeApply(fun, args)         => typeApplyCommon(tree, fun, args)
        case AppliedTypeTree(tpt, args)   => typeApplyCommon(tree, tpt, args)

        case Throw(Ident(name)) =>
          printSingle(tree, name)

        case b @ Bind(name, body) =>
          printMultiline(tree) {
            println(showDefTreeName(b))
            traverse(body)
          }

        case ld @ LabelDef(name, params, rhs) =>
          printMultiline(tree) {
            showNameAndPos(ld)
            traverseList("()", "params")(params)
            traverse(rhs)
          }

        case Function(vparams, body) =>
          printMultiline(tree) {
            traverseList("()", "parameter")(vparams)
            traverse(body)
          }
        case Try(block, catches, finalizer) =>
          printMultiline(tree) {
            traverse(block)
            traverseList("{}", "case")(catches)
            if (finalizer ne EmptyTree)
              traverse(finalizer)
          }

        case Match(selector, cases) =>
          printMultiline(tree) {
            traverse(selector)
            traverseList("", "case")(cases)
          }
        case CaseDef(pat, guard, body) =>
          printMultiline(tree) {
            traverse(pat)
            if (guard ne EmptyTree)
              traverse(guard)
            traverse(body)
          }
        case Block(stats, expr) =>
          printMultiline(tree) {
            traverseList("{}", "statement")(stats)
            traverse(expr)
          }
        case cd @ ClassDef(mods, name, tparams, impl) =>
          printMultiline(tree) {
            printModifiers(cd)
            println(showDefTreeName(cd))
            traverseList("[]", "type parameter")(tparams)
            traverse(impl)
          }
        case md @ ModuleDef(mods, name, impl) =>
          printMultiline(tree) {
            printModifiers(md)
            println(showDefTreeName(md))
            traverse(impl)
          }
        case dd @ DefDef(mods, name, tparams, vparamss, tpt, rhs) =>
          printMultiline(tree) {
            printModifiers(dd)
            println(showDefTreeName(dd))
            traverseList("[]", "type parameter")(tparams)
            vparamss match {
              case Nil        => println("Nil")
              case ListOfNil  => println("List(Nil)")
              case ps  :: Nil =>
                printLine("", "1 parameter list")
                ps foreach traverse
              case pss        =>
                printLine("", pss.length + " parameter lists")
                pss foreach (ps => traverseList("()", "parameter")(ps))
            }
            traverse(tpt)
            traverse(rhs)
          }
        case EmptyTree =>
          println(showName(nme.EMPTY))
        case lit @ Literal(value) =>
          println(showLiteral(lit))
        case New(tpt) =>
          printMultiline(tree)(traverse(tpt))
        case Super(This(qual), mix) =>
          println("Super(This(" + showName(qual) + "), " + showName(mix) + ")")
        case Super(qual, mix) =>
          printMultiline(tree) {
            traverse(qual)
            showName(mix)
          }
        case Template(parents, self, body) =>
          printMultiline(tree) {
            val ps0 = parents map { p =>
              if (p.tpe eq null) p match {
                case x: RefTree => showRefTree(x)
                case x          => showPosition(x) + x
              }
              else showName(newTypeName(p.tpe.typeSymbol.fullName))
            }
            printLine(ps0 mkString ", ", "parents")
            traverse(self)
            traverseList("{}", "statement")(body)
          }
        case This(qual) =>
          printSingle(tree, qual)
        case tt @ TypeTree() =>
          println(showTypeTree(tt))

        case Typed(expr, tpt) =>
          printMultiline(tree) {
            traverse(expr)
            traverse(tpt)
          }
        case vd @ ValDef(mods, name, tpt, rhs) =>
          printMultiline(tree) {
            printModifiers(vd)
            println(showDefTreeName(vd))
            traverse(tpt)
            traverse(rhs)
          }
        case td @ TypeDef(mods, name, tparams, rhs) =>
          printMultiline(tree) {
            printModifiers(td)
            println(showDefTreeName(td))
            traverseList("[]", "type parameter")(tparams)
            traverse(rhs)
          }

        case PackageDef(pid, stats) =>
          printMultiline("PackageDef", "")(pid :: stats foreach traverse)

        case _ =>
          tree match {
            case t: RefTree               => println(showRefTree(t))
            case t if t.productArity == 0 => println(treePrefix(t))
            case t                        => printMultiline(tree)(tree.productIterator foreach traverseAny)
          }
      }
    }
  }

  def printUnit(unit: CompilationUnit) {
    print("// Scala source: " + unit.source + "\n")
    println(Option(unit.body) map (x => nodeToString(x) + "\n") getOrElse "<null>")
  }

  def printAll() {
    print("[[syntax trees at end of " + phase + "]]")
    global.currentRun.units foreach printUnit
  }
}