Issue with rendering MessagePack

[masterkain]

Hello,
I followed the instruction of the wiki in order to add MessagePack support.

I added the corresponding entry in config/initializers/mime_types.rb

Mime::Type.register "application/messagepack", :mpac

Then in controller I have this (Rails 3.2, git master, relevant bits):

class InternalsController < ApplicationController
  respond_to :json, :xml, :mpac
  self.responder = ActsAsApi::Responder

  def user_info
    respond_with(@owner, api_template: :v2_private)
  end

The problem is that Rails is trying to render a messagepack view.

config/initializers/acts_as_api.rb

# Tell acts_as_api that it should accept an additional API format.
ActsAsApi::Config.accepted_api_formats << :mpac

# Add MessagePack as a Rails renderer.
ActionController::Renderers.add :mpac do |object, options|
  self.content_type ||= Mime::MPAC # differs from the wiki, using this can result in a potential error due to loading order, let's go on for now though
  self.response_body = MessagePack.pack(object)
end

# MessagePack doesn't come with the ability to serialize a TimeWithZone, monkey patch.
module ActiveSupport
  class TimeWithZone
    def to_msgpack(out = '')
      self.to_s.to_msgpack(out)
    end
  end
end

RSpec tests fails:

Failure/Error: get 'user_info', format: 'mpac', k: string
ActionView::MissingTemplate:
 Missing template internals/user_info, application/user_info with {:locale=>[:en, :en], :formats=>[:mpac], :handlers=>[:erb, :builder, :coffee, :haml]}. Searched in:
   * "#<RSpec::Rails::ViewRendering::EmptyTemplatePathSetDecorator:0x007fcbe04a7f28>"

Am I missing something? Thanks!

Update: browsing the Rails source code in git I noticed that the ActionController::Renderers.add method never sets respond_body within the block, but just returns a string. So I tried this in the initializer:

ActionController::Renderers.add :mpac do |mpac, options|
  self.content_type ||= Mime::MPAC
  mpac.respond_to?(:to_msgpack) ? mpac.to_msgpack(options) : mpac
end

However rspec still fails with the same error. I can tell that mpac is loaded in renderers:

1.9.3p0 :001 > ActionController::Renderers::RENDERERS
 => #<Set: {:json, :js, :xml, :acts_as_api_jsonp, :mpac}> 

[fabrik42]

So you are using it with Rails 3.2?

I'm not sure if anyone tried combining ActsAsApi::Responder with MessagePack so maybe there is also a bug :/

[masterkain]

MessagePack is also the reason why I can't try out Rubinius, so I might think of dropping it.
In any case I'll try to play with this issue a little more if I have time, will report findings.

[fabrik42]

Closing this for now. Please re-open if issue is still present.