Devise JSON API returning 200 instead of 401 because of redirect

Question

I'm running Angular on a Rails API. For authentication I'm intercepting the 401 status with:

.config(['$httpProvider', function($httpProvider){
    // Prevent rails from making new sessions each time
    $httpProvider.defaults.headers.common['X-CSRF-Token'] = $('meta[name=csrf-token]').attr('content');

    var interceptor = ['$location', '$rootScope', '$q', function($location, $rootScope, $q) {
      function success(response) {
        return response;
      }

      function error(response) {
        if (response.status === 401) {
          $rootScope.$broadcast('event:unauthorized');
          $location.path('/login');
          return response;
        }
        return $q.reject(response);
      }

      return function(promise) {
        return promise.then(success, error);
      };
    }];
    $httpProvider.responseInterceptors.push(interceptor);
  }])

But the interceptor isn't triggering because of the redirect showing a status of 200

Started GET "/api/v1/stages" for 127.0.0.1 at 2014-02-23 04:38:12 +0530
Processing by StagesController#index as HTML
Completed 401 Unauthorized in 5ms


Started GET "/api/v1/users/sign_in" for 127.0.0.1 at 2014-02-23 04:38:12 +0530
Processing by Devise::SessionsController#new as HTML
  Rendered /home/kartikluke/.rvm/gems/ruby-2.0.0-p247/gems/devise-3.2.2/app/views/devise/shared/_links.erb (4.3ms)
  Rendered /home/kartikluke/.rvm/gems/ruby-2.0.0-p247/gems/devise-3.2.2/app/views/devise/sessions/new.html.erb within layouts/application (34.5ms)
Completed 200 OK in 223ms (Views: 171.2ms | ActiveRecord: 5.8ms)

How do I make Devise return a 401 JSON error?

Answer 1

After a lot of searching I found a solution.

I added a custom failure app to Devise:

class JsonFailureApp < Devise::FailureApp
  def respond
    self.status = 401
    self.content_type = 'json'
    self.response_body = '{"error" : "authentication error"}'
  end
end

and added that to Devise:

config.warden do |manager|
    manager.failure_app = JsonFailureApp
end

Now redirect isn't called and instead a status of 401 is registered.