Line number support for REXML documents parsed from files

README.md

Line number support for REXML documents

The Ruby REXML library unfortunately has no built-in support to retrieve line numbers of elements when using Documents (DOM).

This little extension fixes this and gives you Element.start_line ("<" location) and Element.end_line ("/>" location), also for other XML items such as Entities, Decl, etc., just not individual attributes.

Use with doc = XML::parse_xml(file) as replacement for the usual doc = REXML::Document.new(file).

Update: this change makes parsing of certain xml files fail, due to a broken REXML::IOSource#current_line implementation that resets the stream to the wrong location.

xml.rb

require 'rexml/document'

module XML

  def self.parse_xml(file)
    doc = REXML::Document.new
    LineNoTreeParser.new(file, doc).parse
    doc
  end

  module LineNo
    attr_accessor :start_line, :end_line
  end

  class LineNoTreeParser < REXML::Parsers::TreeParser
    def parse
      tag_stack = []
      in_doctype = false
      entities = nil
      begin
        while true
          # BEGIN MONKEY PATCH LineNo
          line = @parser.source.current_line
          # END MONKEY PATCH LineNo

          event = @parser.pull
          #STDERR.puts "TREEPARSER GOT #{event.inspect}"
          case event[0]
            when :end_document
              unless tag_stack.empty?
                #raise ParseException.new("No close tag for #{tag_stack.inspect}")
                raise REXML::ParseException.new("No close tag for #{@build_context.xpath}")
              end
              return
            when :start_element
              tag_stack.push(event[1])
              el = @build_context = @build_context.add_element( event[1] )

              event[2].each do |key, value|
                el.attributes[key]=REXML::Attribute.new(key,value,self)
              end
            when :end_element
              tag_stack.pop
              @build_context = @build_context.parent
            when :text
              if not in_doctype
                if @build_context[-1].instance_of? REXML::Text
                  @build_context[-1] << event[1]
                else
                  @build_context.add(
                      REXML::Text.new(event[1], @build_context.whitespace, nil, true)
                  ) unless (
                  @build_context.ignore_whitespace_nodes and
                      event[1].strip.size==0
                  )
                end
              end
            when :comment
              c = REXML::Comment.new( event[1] )
              @build_context.add( c )
            when :cdata
              c = REXML::CData.new( event[1] )
              @build_context.add( c )
            when :processing_instruction
              @build_context.add( REXML::Instruction.new( event[1], event[2] ) )
            when :end_doctype
              in_doctype = false
              entities.each { |k,v| entities[k] = @build_context.entities[k].value }
              @build_context = @build_context.parent
            when :start_doctype
              doctype = REXML::DocType.new( event[1..-1], @build_context )
              @build_context = doctype
              entities = {}
              in_doctype = true
            when :attlistdecl
              n = REXML::AttlistDecl.new( event[1..-1] )
              @build_context.add( n )
            when :externalentity
              n = REXML::ExternalEntity.new( event[1] )
              @build_context.add( n )
            when :elementdecl
              n = REXML::ElementDecl.new( event[1] )
              @build_context.add(n)
            when :entitydecl
              entities[ event[1] ] = event[2] unless event[2] =~ /PUBLIC|SYSTEM/
              @build_context.add(REXML::Entity.new(event))
            when :notationdecl
              n = REXML::NotationDecl.new( *event[1..-1] )
              @build_context.add( n )
            when :xmldecl
              x = REXML::XMLDecl.new( event[1], event[2], event[3] )
              @build_context.add( x )
          end

          # BEGIN MONKEY PATCH LineNo
          @build_context.extend(LineNo)
          @build_context.start_line = line[1]
          @build_context.end_line = line[2]
          # END MONKEY PATCH LineNo

        end
      rescue REXML::Validation::ValidationException
        raise
      rescue REXML::UndefinedNamespaceException
        raise
      rescue
        raise REXML::ParseException.new( $!.message, @parser.source, @parser, $! )
      end
    end
  end
end