session

# File actionpack/lib/action_controller/cgi_process.rb, line 111
    def session
      unless defined?(@session)
        if @session_options == false
          @session = Hash.new
        else
          stale_session_check! do
            if cookie_only? && query_parameters[session_options_with_string_keys['session_key']]
              raise SessionFixationAttempt
            end
            case value = session_options_with_string_keys['new_session']
              when true
                @session = new_session
              when false
                begin
                  @session = CGI::Session.new(@cgi, session_options_with_string_keys)
                # CGI::Session raises ArgumentError if 'new_session' == false
                # and no session cookie or query param is present.
                rescue ArgumentError
                  @session = Hash.new
                end
              when nil
                @session = CGI::Session.new(@cgi, session_options_with_string_keys)
              else
                raise ArgumentError, "Invalid new_session option: #{value}"
            end
            @session['__valid_session']
          end
        end
      end
      @session
    end