RSpec differ_from matcher (calls other matchers)

array_matcher.rb

module RSpec
  module Matchers
    class ArrayMatcher < Matcher
      def initialize expected
        super(:be_different_array_from, expected) do |*_expected|
          match_for_should do |actual|
            perform_match(actual, _expected[0])
            @extra + @missing != []
          end
        
          match_for_should_not do |actual|
            perform_match(actual, _expected[0])
            @extra + @missing == []
          end 
      
          def perform_match(actual, expected)
            @extra = actual - expected
            @missing = expected - actual
          end

          def failure_message_for_should
            "expected a difference in the two lists, but got none"
          end

          failure_message_for_should_not do |actual|
            "expected no difference, but result #{
              [ (@missing.empty? ? nil : 'lacks '+@missing.sort.inspect),
                (@extra.empty? ? nil : 'has extra '+@extra.sort.inspect)
              ].compact * ' and '
            }"
          end
        end
      end
    end

    def be_different_array_from(expected)
      ArrayMatcher.new(expected)
    end
  end
end

diff_matcher.rb

require 'pathname'
  
module RSpec
  module Matchers
    def differ_from(expected)
      case expected
      when Pathname
        FileMatcher.new(expected)
      when Array
        ArrayMatcher.new(expected)
      when String
        FileMatcher.new(expected) 
      else  
        raise "DiffMatcher doesn't know how to match a #{expected.class}"
      end
    end   
  end       
end

file_matcher.rb

require 'diff/lcs'
  
module RSpec
  module Matchers
    class FileMatcher < Matcher
      def initialize expected
        super(:have_different_contents, expected) do |*_expected|
          match_for_should do |actual|
            perform_match(actual, _expected[0])
          end
      
          match_for_should_not do |actual|
            !perform_match(actual, _expected[0])
          end 
      
          def perform_match(actual, expected)
            expected = File.open(expected).read if expected.is_a?(Pathname)
            expected = expected.scan(/[^\n]+/) unless expected.is_a?(Array)

            actual = File.open(actual).read if actual.is_a?(Pathname)
            actual = actual.scan(/[^\n]+/) unless actual.is_a?(Array)

            differences = Diff::LCS::diff(expected, actual)
            @diff = differences.map do |chunk|
                added_at = (add = chunk.detect{|d| d.action == '+'}) && add.position+1
                removed_at = (remove = chunk.detect{|d| d.action == '-'}) && remove.position+1
                "Line #{added_at}/#{removed_at}:\n"+
                chunk.map do |change|
                  "#{change.action} #{change.element}"
                end*"\n"
              end*"\n"
            @diff != ''
          end

          def failure_message_for_should
            "expected a difference, but got none"
          end

          failure_message_for_should_not do |actual|
            "expected no difference, but got:\n#{@diff}"
          end
        end
      end
    end

    def have_different_contents(expected)
      FileMatcher.new(expected)
    end
  end
end

string_matcher.rb

require 'diff/lcs'
  
module RSpec
  module Matchers
    def have_different_contents(expected)
      Matcher.new :have_different_contents, expected do |*_expected|
        match_for_should do |actual|
          perform_match(actual, _expected)
        end 
          
        match_for_should_not do |actual|
          !perform_match(actual, _expected)
        end 
          
        def perform_match(actual, expected)
          expected_lines = expected.scan(/[^\n]+/)
          actual_lines = actual.scan(/[^\n]+/)
          differences = Diff::LCS::diff(expected_lines, actual_lines)
          @diff = differences.map do |chunk|
              added_at = (add = chunk.detect{|d| d.action == '+'}) && add.position+1
              removed_at = (remove = chunk.detect{|d| d.action == '-'}) && remove.position+1
              "Line #{added_at}/#{removed_at}:\n"+
              chunk.map do |change|
                "#{change.action} #{change.element}"
              end*"\n"
            end*"\n"
          @diff != '' 
        end     
                  
        def failure_message_for_should
          "expected a difference, but got none"
        end 
          
        failure_message_for_should_not do |actual|
          "expected no difference, but got:\n#{@diff}"
        end 
      end 
    end
  end     
end