Rails 3, HTTP extensions (WebDAV) and Rack App mounting

A more readable version of this here:

Hello,

1 The following is more to point out to the code devs an issue of
rails that can be percieved as a flaw.
2 And also me asking some oppinions from people who know better.

I want to add WebDAV to my Rails 3 App with Warden authentication. My
warden middleware is injected via Devise.

http://github.com/chrisroberts/dav4rack
http://github.com/hassox/warden
http://github.com/plataformatec/devise

I cannot mount DAV4Rack handlers from inside rails app (routes), like
this:

# in routes.rb
mount DAV4Rack::Handler.new(
  :root => Rails.root.to_s, # <= it's just an example
  :root_uri_path => '/webdav',
  :resource_class => Dav::DocumentResource # <= my custom

resource, you could use FileResource from dav4rack
), :at => “/webdav”

because rails validates HTTP verbs (GET POST PUT …), and webdav uses
HTTP extensions like PROPFIND that do not validate, throwing the
following exception:

ActionController::UnknownHttpMethod (PROPFIND, accepted HTTP

methods are get, head, put, post, delete, and options)

This validation takes place in ActionDispatch:

/usr/local/lib/ruby/gems/1.9.1/gems/actionpack-3.0.0/lib/

action_dispatch/http/request.rb +56 +72
in (56) “def request_method” and (72) “def method”

Sample code from ActionDispatch that does the validation, to make
things clear:

def method
  @method ||= begin
    method = env["rack.methodoverride.original_method"] ||

env[‘REQUEST_METHOD’]
HTTP_METHOD_LOOKUP[method] ||
raise(ActionController::UnknownHttpMethod, “#{method}, accepted HTTP
methods are #{HTTP_METHODS.to_sentence(:locale => :en)}”)
method
end
end

To add DAV4Rack handlers to the rails app I have to mount the handler
outside of ActionDispatch, at rack level, like this:

# config.ru
require ::File.expand_path('../config/environment',  __FILE__)
require 'dav4rack/interceptor'
require 'dav/document_resource'

app = Rack::Builder.new{
  map '/webdav/' do
    run DAV4Rack::Handler.new(
      :root => Rails.root.to_s,
      :root_uri_path => '/webdav',
      :resource_class => Dav::DocumentResource
    )
  end

  map '/' do
    use DAV4Rack::Interceptor, :mappings => {
      '/webdav/' => {
        :resource_class => Dav::DocumentResource
      },
    }
    run Pmp::Application
  end
}.to_app
run app

Now I have Webdav support in my application. But It still needs
authentication, and for that I’d like to use warden.

# in document_resource.rb
def check_authentication
  puts request.env['warden'] # nil :(
end

Warden is nil because my DAV4Rack::Handler is mounted above the
session and warden middleware.
Using “rake middleware” to inspect my stack I can see the following:

> rake middleware
use ActionDispatch::Static
use Rack::Lock
use ActiveSupport::Cache::Strategy::LocalCache
use Rack::Runtime
use Rails::Rack::Logger
use ActionDispatch::ShowExceptions
use ActionDispatch::RemoteIp
use Rack::Sendfile
use ActionDispatch::Callbacks
use ActiveRecord::ConnectionAdapters::ConnectionManagement
use ActiveRecord::QueryCache
use ActionDispatch::Cookies
use ActionDispatch::Session::CookieStore
use ActionDispatch::Flash
use ActionDispatch::ParamsParser
use Rack::MethodOverride
use ActionDispatch::Head
use ActionDispatch::BestStandardsSupport
use Warden::Manager
run Pmp::Application.routes

I believe that by wrapping “Pmp::Application.routes” with DAV handler
(just like I do above for “Pmp::Application” in config.ru) will inject
my webdav handler in the stack at the right place to satisfy the two
conditions:

  1. Be above ActionDispatch method validation code, to avoid
    ActionController::UnknownHttpMethod
  2. Be below session and Warden::Manager so I can use warden
    authentication.

How to do that? Looking at “rake middleware” otput it seems obvious to
override the “Pmp::Application.routes” method:

# in my app at APP_ROOT/config/application.rb
# override the routes method inherited from

Rails::Application#routes
def routes
routes_app = super
app = Rack::Builder.new {
map ‘/webdav/’ do
run DAV4Rack::Handler.new(
:root => Rails.root.to_s,
:root_uri_path => ‘/webdav’,
:resource_class => Dav::DocumentResource
)
end

    map '/' do
      use DAV4Rack::Interceptor, :mappings => {
        '/webdav/' => {
          :resource_class => Dav::DocumentResource
        },
      }
      run routes_app
    end
  }.to_app

  class << app; self end.class_eval do
    attr_accessor :routes_app
    def method_missing(sym, *args, &block)
      routes_app.send sym, *args, &block
    end
  end
  app.routes_app = routes_app

  app
end

Because our replacing rack application “app” will be asked a few
methods down the chain, that we do not implement, we delegate theese
to the old original application “routes_app” with a little
method_missing magic.

And voila: evrything is working!
Great success.

Only one problem: I don’t like it. There must be a better way to do
all this enveloping, other than overriding routes method.

THE BIG QUESTION:

IS THERE A BETTER WAY TO ADD A RACK APP JUST ABOVE THE
“Pmp::Application#routes” APP BY MEANS OF RACK MOUNT OR OTHER ???

THE BIG CONCLUSION

  1. The “mount” semantics in routes.rb should be rack-level (not rails/
    railtie/whatever), to allow, in this way, hadling of HTTP extensions,
    or at least have a method for this case “mount_rack”

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs