tdiff's Introduction

TDiff

Source
Issues
Postmodern (postmodern.mod3 at gmail.com)

Description

Calculates the differences between two tree-like structures. Similar to Rubys built-in TSort module.

Features

Provides the {TDiff} mixin.
Provides the {TDiff::Unordered} mixin for unordered diffing.
Allows custom node equality and traversal logic by overriding the {TDiff#tdiff_equal} and {TDiff#tdiff_each_child} methods.
Implements the Longest Common Subsequence (LCS) algorithm.

Examples

Diff two HTML documents:

require 'nokogiri'
require 'tdiff'

class Nokogiri::XML::Node

  include TDiff

  def tdiff_equal(node)
    if (self.text? && node.text?)
      self.text == node.text
    elsif (self.respond_to?(:root) && node.respond_to?(:root))
      self.root.tdiff_equal(node.root)
    elsif (self.respond_to?(:name) && node.respond_to?(:name))
      self.name == node.name
    else
      false
    end
  end

  def tdiff_each_child(node,&block)
    node.children.each(&block)
  end

end

doc1 = Nokogiri::HTML('<div><p>one</p> <p>three</p></div>')
doc2 = Nokogiri::HTML('<div><p>one</p> <p>two</p> <p>three</p></div>')

doc1.at('div').tdiff(doc2.at('div')) do |change,node|
  puts "#{change} #{node.to_html}".ljust(30) + node.parent.path
end

Output

+ <p>one</p>                  /html/body/div
+                             /html/body/div
  <p>one</p>                  /html/body/div
                              /html/body/div
  <p>three</p>                /html/body/div
- one                         /html/body/div/p[1]
+ two                         /html/body/div/p[2]
  three                       /html/body/div/p[2]