Fix for problem between cucumber/Mundo Pepino/Webrat and Rack::Rewrite

rack_utils_header_hash_extension.rb

# I had Cucumber / Mundo Pepino configured with Webrat and used jtrupiano's Rack::Rewrite (https://github.com/jtrupiano/rack-rewrite) to handle redirections between some old URLs and new ones
# When I tested if redirections were being handled correctly I encountered with a big issue: URL of the redirection appeared to be nil.
# I tested it manually and redirections were fine, so I though this could be a problem with the interaction between Rack::Rewrite and Webrat.
# After some dig and debug on the gems (cucumber, webrat and rack mostly) code I found the problem:

# Line 283 of lib/webrat/core/session.rb
#
#    def response_location
#      response.headers["Location"]
#    end

#  puts response.headers #--> {"Location" : "http://www.example.com/new-url"}
#  puts response.headers["Location"] #--> nil

# So, although the header is there, when requested it returns nil... WTF?

# response.headers is an instance of Rack::Utils::HeaderHash class, so I went to the code. It's a class that inherits from Hash and redefines [] and []= methods

# Line 210 of lib/rack/utils.rb on Rack gem
#
#      def [](k)
#        super @names[k.downcase]
#      end
#
#      def []=(k, v)
#        delete k
#        @names[k.downcase] = k
#        super k, v
#      end

# I'm not quite sure on why it behaves like this, but when response["Location"] is requested @names[k.downcase] (this means @names["location"]) is 'nil' so we only need to call super with the actual key.

# Following code opens Rack::Utils::HeaderHash class and redefines [] method. Now response["Location"] returns "http://www.example.com/new-url"

# Strange bug on the interaction between Capybara and Rack found and fixed

module Rack
  module Utils
    class HeaderHash
      def [](k)
        super(@names[k.downcase] || k)
      end
    end
  end
end