default_controller_and_action

# File actionpack/lib/action_dispatch/routing/mapper.rb, line 142
          def default_controller_and_action(to_shorthand=nil)
            if to.respond_to?(:call)
              { }
            else
              if to.is_a?(String)
                controller, action = to.split('#')
              elsif to.is_a?(Symbol)
                action = to.to_s
              end

              controller ||= default_controller
              action     ||= default_action

              unless controller.is_a?(Regexp) || to_shorthand
                controller = [@scope[:module], controller].compact.join("/").presence
              end

              if controller.is_a?(String) && controller =~ %{\A/}
                raise ArgumentError, "controller name should not start with a slash"
              end

              controller = controller.to_s unless controller.is_a?(Regexp)
              action     = action.to_s     unless action.is_a?(Regexp)

              if controller.blank? && segment_keys.exclude?("controller")
                raise ArgumentError, "missing :controller"
              end

              if action.blank? && segment_keys.exclude?("action")
                raise ArgumentError, "missing :action"
              end

              { :controller => controller, :action => action }.tap do |hash|
                hash.delete(:controller) if hash[:controller].blank?
                hash.delete(:action)     if hash[:action].blank?
              end
            end
          end