How do I tell the line number for a node using the Nokogiri reader interface?

Question

I'm trying to write a Nokogiri script that will grep XML for text nodes containing ASCII double-quotes («"»). Since I want a grep-like output I need the line number, and the contents of each line. However, I am unable to see how to tell the line number where the element starts at. Here is my code:

require 'rubygems'
require 'nokogiri'

ARGV.each do |filename|
    xml_stream = File.open(filename)
    reader = Nokogiri::XML::Reader(xml_stream)
    titles = []
    text = ''
    grab_text = false
    reader.each do |elem|
        if elem.node_type == Nokogiri::XML::Node::TEXT_NODE
            data = elem.value
            lines = data.split(/\n/, -1);

            lines.each_with_index do |line, idx|
                if (line =~ /"/) then
                    STDOUT.printf "%s:%d:%s\n", filename, elem.line()+idx, line
                end
            end
        end
    end
end

elem.line() does not work.

Answer 1

XML and parsers don't really have a concept of line numbers. You're talking about the physical layout of the file.

You can play a game with the parser using accessors looking for text nodes containing linefeeds and/or carriage returns but that can be thrown off because XML allows nested nodes.

require 'nokogiri'

xml =<<EOT_XML
<atag>
  <btag>
    <ctag 
      id="another_node">
      other text
    </ctag>
  </btag>
  <btag>
    <ctag id="another_node2">yet
                             another
                             text</ctag>
    </btag>
  <btag>
    <ctag id="this_node">this text</ctag>
  </btag>
</atag>
EOT_XML

doc = Nokogiri::XML(xml)

# find a particular node via CSS accessor
doc.at('ctag#this_node').text # => "this text"

# count how many "lines" there are in the document
doc.search('*/text()').select{ |t| t.text[/[\r\n]/] }.size # => 12

# walk the nodes looking for a particular string, counting lines as you go
content_at = []
doc.search('*/text()').each do |n|
  content_at << [n.line, n.text] if (n.text['this text'])
end
content_at # => [[14, "this text"]]

This works because of the parser's ability to figure out what is a text node and cleanly return it, without relying on regex or text matches.

---

EDIT: I went through some old code, snooped around in Nokogiri's docs some, and came up with the above edited changes. It's working correctly, including working with some pathological cases. Nokogiri FTW!