Ruby Nokogiri: Return a parent attribute value based on a sub element attribute match.

test.rb

xml = "
<levels>
  <lvl attr = 'x'>
    <lvl2>
      <lvl3 n = 'unique_value 1A'>'</lvl3>
    </lvl2>
  </lvl1>

  <lvl attr = 'y' another_attr = 'z'>
    <lvl2>
      <lvl3 n = 'unique_value 1B'>'</lvl3>
    </lvl2>
  </lvl1>
</levels>
"

require 'nokogiri'
require 'pp'

doc = Nokogiri::XML(xml)


puts "Should return 'y'"
puts element = doc.at_xpath(".//*/*[@n='unique_value 1B']")
puts attribute = (element.ancestors('lvl').first || { })['attr']

puts ''
puts "Should return 'x'"
puts element = doc.at_xpath(".//*/*[@n='unique_value 1A']")
puts attribute = (element.ancestors('lvl').first || { })['attr']

puts ''
puts "Should dump all parent attributes"
puts element = doc.at_xpath(".//*/*[@n='unique_value 1B']")
puts attributes = (element.ancestors('lvl').first  || { }).attributes()
attributes.each { | k, v | pp "#{k}: #{v}" }