failing_test.rb

  def test_routes_with_format_requirements
    ActionController::Routing.with_controllers(['pages']) do
      set.draw do |map|
        map.public_view ':id.:format',
          :controller   => 'pages',
          :action       => 'show',
          :requirements => { :method =>'get',  :format =>/html/i}
        map.public_view ':id.:format',
          :controller   => 'pages',
          :action       => 'old_show',
          :requirements => { :method =>'get',  :format =>/htm/i}
      end

      assert_equal({:controller => 'pages', :action => 'show',     :id => '10',
                    :method     => 'get',   :format => 'html'},
                    set.recognize_path('/10.html'))
      assert_equal({:controller => 'pages', :action => 'old_show', :id => '10',
                    :method     => 'get',   :format => 'htm'},
                    set.recognize_path('/10.htm'))
    end
  end

format_in_builder.rb

# actionpack/lib/action_controller/routing/builder.rb

      def segment_for(string)
        segment =
          case string
            when  /\A\.(:format)?\// 
              OptionalFormatSegment.new

format_in_segments.rb

# actionpack/lib/action_controller/routing/segments.rb

    # The OptionalFormatSegment allows for any resource route to have an optional
    # :format, which decreases the amount of routes created by 50%.
    class OptionalFormatSegment < DynamicSegment
    
      def initialize(key = nil, options = {})
        super(:format, {:optional => true}.merge(options))            
      end
    
      def interpolation_chunk
        "." + super
      end
    
      def regexp_chunk
        '/|(\.[^/?\.]+)?'
      end
    
      def to_s
        '(.:format)?'
      end

fromat_in_recognition_optimisation.rb

# actionpack/lib/action_controller/routing/recognition_optimisation.rb

      def to_plain_segments(str)
        str = str.dup
        str.sub!(/^\/+/,'')
        str.sub!(/\/+$/,'')
        segments = str.split(/\.[^\/]+\/+|\/+|\.[^\/]+\Z/) # cut off ".format" also
        segments << nil
        segments
      end

test_failure.txt

  1) Failure:
test_routes_with_format_requirements(RouteSetTest)
    [./test/controller/routing_test.rb:1859:in `test_routes_with_format_requirements'
     ./test/../lib/action_controller/routing.rb:290:in `with_controllers'
     ./test/controller/routing_test.rb:1843:in `test_routes_with_format_requirements'
     /Library/Ruby/Gems/1.8/gems/mocha-0.9.7/lib/mocha/integration/test_unit/ruby_version_186_and_above.rb:19:in `__send__'
     /Library/Ruby/Gems/1.8/gems/mocha-0.9.7/lib/mocha/integration/test_unit/ruby_version_186_and_above.rb:19:in `run']:
<{:action=>"old_show",
 :format=>"htm",
 :method=>"get",
 :controller=>"pages",
 :id=>"10"}> expected but was
<{:action=>"show",
 :format=>"htm",
 :method=>"get",
 :controller=>"pages",
 :id=>"10"}>.