When providing an alternative action for rendering to respond_with, the action is ignored when the resourceful response is successful, because options[:action] is deleted for reasons I can't determine. Changing line 11 of responder.rb, as demonstrated in patched_responder.rb, fixes this so that the action is correctly passed to default_render. T…

0_messages_controller.rb

class MessagesController < ActionController::Base
  respond_to :html
  
  def show
    resource = Message.find(params[:id])
    action = resource.sent? ? :edit : :show
    respond_with(resource, :action => action)
  end
  
  def edit
  end
end

1_responder.rb

module ActionController
  class Responder
    # ...
    def initialize(controller, resources, options={})
      @controller = controller
      @request = @controller.request
      @format = @controller.formats.first
      @resource = resources.last
      @resources = resources
      @options = options
      @action = options.delete(:action)
      @default_response = options.delete(:default_response)
    end
    # ...
    def to_html
      default_render
    rescue ActionView::MissingTemplate => e
      navigation_behavior(e)
    end
    # ...
    def navigation_behavior(error)
      if get?
        raise error
      elsif has_errors? && default_action
        render :action => default_action
      else
        redirect_to navigation_location
      end
    end
    # ...
    def default_render
      if @default_response
        @default_response.call(options)
      else
        controller.default_render(options)
      end
    end
    # ...
    def default_action
      @action ||= DEFAULT_ACTIONS_FOR_VERBS[request.request_method_symbol]
    end
  end
end

2_patched_responder.rb

module ActionController
  class Responder
    # ...
    def initialize(controller, resources, options={})
      @controller = controller
      @request = @controller.request
      @format = @controller.formats.first
      @resource = resources.last
      @resources = resources
      @options = options
      @action = options[:action]
      @default_response = options.delete(:default_response)
    end
    # ...
  end
end