Scala example source code file (SymbolicXMLBuilder.scala)

This example Scala source code file (SymbolicXMLBuilder.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

collection, compiler, ident, list, literal, ll, nametype, new, nil, nsc, position, string, tree

The SymbolicXMLBuilder.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author Burak Emir
 */

package scala.tools.nsc
package ast.parser

import scala.collection.{ mutable, immutable }
import symtab.Flags.MUTABLE
import scala.reflect.internal.util.StringOps.splitWhere

/** This class builds instance of `Tree` that represent XML.
 *
 *  Note from martin: This needs to have its position info reworked. I don't
 *  understand exactly what's done here. To make validation pass, I set many
 *  positions to be transparent. Not sure this is a good idea for navigating
 *  XML trees in the IDE but it's the best I can do right now. If someone
 *  who understands this part better wants to give it a shot, please do!
 *
 *  @author  Burak Emir
 *  @version 1.0
 */
abstract class SymbolicXMLBuilder(p: Parsers#Parser, preserveWS: Boolean) {
  val global: Global
  import global._

  private[parser] var isPattern: Boolean = _

  private object xmltypes extends TypeNames {
    val _Comment: NameType             = "Comment"
    val _Elem: NameType                = "Elem"
    val _EntityRef: NameType           = "EntityRef"
    val _Group: NameType               = "Group"
    val _MetaData: NameType            = "MetaData"
    val _NamespaceBinding: NameType    = "NamespaceBinding"
    val _NodeBuffer: NameType          = "NodeBuffer"
    val _PrefixedAttribute: NameType   = "PrefixedAttribute"
    val _ProcInstr: NameType           = "ProcInstr"
    val _Text: NameType                = "Text"
    val _Unparsed: NameType            = "Unparsed"
    val _UnprefixedAttribute: NameType = "UnprefixedAttribute"
  }

  private object xmlterms extends TermNames {
    val _Null: NameType     = "Null"
    val __Elem: NameType    = "Elem"
    val __Text: NameType    = "Text"
    val _buf: NameType      = "$buf"
    val _md: NameType       = "$md"
    val _plus: NameType     = "$amp$plus"
    val _scope: NameType    = "$scope"
    val _tmpscope: NameType = "$tmpscope"
    val _xml: NameType      = "xml"
  }

  import xmltypes.{_Comment, _Elem, _EntityRef, _Group, _MetaData, _NamespaceBinding, _NodeBuffer,
    _PrefixedAttribute, _ProcInstr, _Text, _Unparsed, _UnprefixedAttribute}

  import xmlterms.{_Null, __Elem, __Text, _buf, _md, _plus, _scope, _tmpscope, _xml}

  // convenience methods
  private def LL[A](x: A*): List[List[A]] = List(List(x:_*))
  private def const(x: Any) = Literal(Constant(x))
  private def wild                          = Ident(nme.WILDCARD)
  private def wildStar                      = Ident(tpnme.WILDCARD_STAR)
  private def _scala(name: Name)            = Select(Select(Ident(nme.ROOTPKG), nme.scala_), name)
  private def _scala_xml(name: Name)        = Select(_scala(_xml), name)

  private def _scala_xml_Comment            = _scala_xml(_Comment)
  private def _scala_xml_Elem               = _scala_xml(_Elem)
  private def _scala_xml_EntityRef          = _scala_xml(_EntityRef)
  private def _scala_xml_Group              = _scala_xml(_Group)
  private def _scala_xml_MetaData           = _scala_xml(_MetaData)
  private def _scala_xml_NamespaceBinding   = _scala_xml(_NamespaceBinding)
  private def _scala_xml_NodeBuffer         = _scala_xml(_NodeBuffer)
  private def _scala_xml_Null               = _scala_xml(_Null)
  private def _scala_xml_PrefixedAttribute  = _scala_xml(_PrefixedAttribute)
  private def _scala_xml_ProcInstr          = _scala_xml(_ProcInstr)
  private def _scala_xml_Text               = _scala_xml(_Text)
  private def _scala_xml_Unparsed           = _scala_xml(_Unparsed)
  private def _scala_xml_UnprefixedAttribute= _scala_xml(_UnprefixedAttribute)
  private def _scala_xml__Elem              = _scala_xml(__Elem)
  private def _scala_xml__Text              = _scala_xml(__Text)

  /** Wildly wrong documentation deleted in favor of "self-documenting code." */
  protected def mkXML(
    pos: Position,
    isPattern: Boolean,
    pre: Tree,
    label: Tree,
    attrs: Tree,
    scope: Tree,
    empty: Boolean,
    children: Seq[Tree]): Tree =
  {
    def starArgs =
      if (children.isEmpty) Nil
      else List(Typed(makeXMLseq(pos, children), wildStar))

    def pat    = Apply(_scala_xml__Elem, List(pre, label, wild, wild) ::: convertToTextPat(children))
    def nonpat = New(_scala_xml_Elem, List(List(pre, label, attrs, scope, if (empty) Literal(Constant(true)) else Literal(Constant(false))) ::: starArgs))

    atPos(pos) { if (isPattern) pat else nonpat }
  }

  final def entityRef(pos: Position, n: String) =
    atPos(pos)( New(_scala_xml_EntityRef, LL(const(n))) )

  // create scala.xml.Text here <: scala.xml.Node
  final def text(pos: Position, txt: String): Tree = atPos(pos) {
    if (isPattern) makeTextPat(const(txt))
    else makeText1(const(txt))
  }

  def makeTextPat(txt: Tree)                = Apply(_scala_xml__Text, List(txt))
  def makeText1(txt: Tree)                  = New(_scala_xml_Text, LL(txt))
  def comment(pos: Position, text: String)  = atPos(pos)( Comment(const(text)) )
  def charData(pos: Position, txt: String)  = atPos(pos)( makeText1(const(txt)) )

  def procInstr(pos: Position, target: String, txt: String) =
    atPos(pos)( ProcInstr(const(target), const(txt)) )

  protected def Comment(txt: Tree)                  = New(_scala_xml_Comment, LL(txt))
  protected def ProcInstr(target: Tree, txt: Tree)  = New(_scala_xml_ProcInstr, LL(target, txt))

  /** @todo: attributes */
  def makeXMLpat(pos: Position, n: String, args: Seq[Tree]): Tree = {
    val (prepat, labpat) = splitPrefix(n) match {
      case (Some(pre), rest)  => (const(pre), const(rest))
      case _                  => (wild, const(n))
    }
    mkXML(pos, isPattern = true, prepat, labpat, null, null, empty = false, args)
  }

  protected def convertToTextPat(t: Tree): Tree = t match {
    case _: Literal => makeTextPat(t)
    case _          => t
  }
  protected def convertToTextPat(buf: Seq[Tree]): List[Tree] =
    (buf map convertToTextPat).toList

  def parseAttribute(pos: Position, s: String): Tree = {
    import xml.Utility.parseAttributeValue

    parseAttributeValue(s, text(pos, _), entityRef(pos, _)) match {
      case Nil      => gen.mkNil
      case t :: Nil => t
      case ts       => makeXMLseq(pos, ts.toList)
    }
  }

  def isEmptyText(t: Tree) = t match {
    case Literal(Constant("")) => true
    case _ => false
  }

  /** could optimize if args.length == 0, args.length == 1 AND args(0) is <: Node. */
  def makeXMLseq(pos: Position, args: Seq[Tree]) = {
    val buffer = ValDef(NoMods, _buf, TypeTree(), New(_scala_xml_NodeBuffer, ListOfNil))
    val applies = args filterNot isEmptyText map (t => Apply(Select(Ident(_buf), _plus), List(t)))

    atPos(pos)( Block(buffer :: applies.toList, Ident(_buf)) )
  }

  /** Returns (Some(prefix) | None, rest) based on position of ':' */
  def splitPrefix(name: String): (Option[String], String) = splitWhere(name, _ == ':', doDropIndex = true) match {
    case Some((pre, rest))  => (Some(pre), rest)
    case _                  => (None, name)
  }

  /** Various node constructions. */
  def group(pos: Position, args: Seq[Tree]): Tree =
    atPos(pos)( New(_scala_xml_Group, LL(makeXMLseq(pos, args))) )

  def unparsed(pos: Position, str: String): Tree =
    atPos(pos)( New(_scala_xml_Unparsed, LL(const(str))) )

  def element(pos: Position, qname: String, attrMap: mutable.Map[String, Tree], empty: Boolean, args: Seq[Tree]): Tree = {
    def handleNamespaceBinding(pre: String, z: String): Tree = {
      def mkAssign(t: Tree): Tree = Assign(
        Ident(_tmpscope),
        New(_scala_xml_NamespaceBinding, LL(const(pre), t, Ident(_tmpscope)))
      )

      val uri1 = attrMap(z) match {
        case Apply(_, List(uri @ Literal(Constant(_)))) => mkAssign(uri)
        case Select(_, nme.Nil)                         => mkAssign(const(null))  // allow for xmlns="" -- bug #1626
        case x                                          => mkAssign(x)
      }
      attrMap -= z
      uri1
    }

    /* Extract all the namespaces from the attribute map. */
    val namespaces: List[Tree] =
      for (z <- attrMap.keys.toList ; if z startsWith "xmlns") yield {
        val ns = splitPrefix(z) match {
          case (Some(_), rest)  => rest
          case _                => null
        }
        handleNamespaceBinding(ns, z)
      }

    val (pre, newlabel) = splitPrefix(qname) match {
      case (Some(p), x) => (p, x)
      case (None, x)    => (null, x)
    }

    def mkAttributeTree(pre: String, key: String, value: Tree) = atPos(pos.makeTransparent) {
      // XXX this is where we'd like to put Select(value, nme.toString_) for #1787
      // after we resolve the Some(foo) situation.
      val baseArgs = List(const(key), value, Ident(_md))
      val (clazz, attrArgs) =
        if (pre == null) (_scala_xml_UnprefixedAttribute, baseArgs)
                    else (_scala_xml_PrefixedAttribute  , const(pre) :: baseArgs)

      Assign(Ident(_md), New(clazz, LL(attrArgs: _*)))
    }

    def handlePrefixedAttribute(pre: String, key: String, value: Tree)  = mkAttributeTree(pre, key, value)
    def handleUnprefixedAttribute(key: String, value: Tree)             = mkAttributeTree(null, key, value)

    val attributes: List[Tree] =
      for ((k, v) <- attrMap.toList.reverse) yield splitPrefix(k) match {
        case (Some(pre), rest)  => handlePrefixedAttribute(pre, rest, v)
        case _                  => handleUnprefixedAttribute(k, v)
      }

    lazy val scopeDef     = ValDef(NoMods, _scope, _scala_xml_NamespaceBinding, Ident(_tmpscope))
    lazy val tmpScopeDef  = ValDef(Modifiers(MUTABLE), _tmpscope, _scala_xml_NamespaceBinding, Ident(_scope))
    lazy val metadataDef  = ValDef(Modifiers(MUTABLE), _md, _scala_xml_MetaData, _scala_xml_Null)
    val makeSymbolicAttrs = if (!attributes.isEmpty) Ident(_md) else _scala_xml_Null

    val (attrResult, nsResult) =
      (attributes.isEmpty, namespaces.isEmpty) match {
        case (true ,  true)   => (Nil, Nil)
        case (true , false)   => (scopeDef :: Nil, tmpScopeDef :: namespaces)
        case (false,  true)   => (metadataDef :: attributes, Nil)
        case (false, false)   => (scopeDef :: metadataDef :: attributes, tmpScopeDef :: namespaces)
      }

    val body = mkXML(
      pos.makeTransparent,
      isPattern = false,
      const(pre),
      const(newlabel),
      makeSymbolicAttrs,
      Ident(_scope),
      empty,
      args
    )

    atPos(pos.makeTransparent)( Block(nsResult, Block(attrResult, body)) )
  }
}