Rails routing. Singular resource - ruby-on-rails

Question

I've got Rails routing problem. I would like to use singular resource with user controller but it doesn't work as I expected. Here is the fragment of my routes.rb file:
scope :module => "frontend" do
root :to => "home#index"
resource :user, :controller => "user"
get "/sign_up" => "user#new"
get "/sign_in" => "user#sign_in"
get "/sign_out" => "user#sign_out"
post "/authenticate" => "user#authenticate"
resources :articles
resources :article_categories
end
I thought it will work when I'll use for example "/user" or "/user/new" URL but it didn't. I get a routing error:
No route matches {:controller=>"frontend/user"}
The 'rake routes' command output is:
user POST /user(.:format) frontend/user#create
new_user GET /user/new(.:format) frontend/user#new
edit_user GET /user/edit(.:format) frontend/user#edit
GET /user(.:format) frontend/user#show
PUT /user(.:format) frontend/user#update
DELETE /user(.:format) frontend/user#destroy
sign_up GET /sign_up(.:format) frontend/user#new
sign_in GET /sign_in(.:format) frontend/user#sign_in
sign_out GET /sign_out(.:format) frontend/user#sign_out
authenticate POST /authenticate(.:format) frontend/user#authenticate
What is interesting, when I add route for index action in user controller, like this:
scope :module => "frontend" do
root :to => "home#index"
resource :user, :controller => "user"
get "/user" => "user#index"
get "/sign_up" => "user#new"
get "/sign_in" => "user#sign_in"
get "/sign_out" => "user#sign_out"
post "/authenticate" => "user#authenticate"
resources :articles
resources :article_categories
end
...it works!
But index action is not defined in user controller!
'rake routes' command returns double line for GET /user
GET /user(.:format) frontend/user#show
GET /user(.:format) frontend/user#index
so I suppose that's not the solution. Other actions assigned to '/users' URL don't work.
Is it necessary to define the route for the index action like
get "/controller_name" => "controller_name#index"
What am I doing wrong?

Answer 1

Defining a singular resource in your routes will not generate a route to an index action by design. The singular resource implies you're always going to lookup this resource without specifying an ID and consequently a get to index for a singular resource just doesn't make logical sense. So, a GET to your url "/user" will route to a show action for that singular resource and not an index.
EDIT: Since your issue isn't obvious, I'd simplify your routes until you can at least hit the controller you'd expect and then build from there.
config/routes.rb
scope :module=>"frontend" do
resource :user
end
#ensure you don't have any other user routes listed before this that would match "/user".
app/controllers/frontend/users_controller.rb
module Frontend
class UsersController < ApplicationController
def show
raise "in frontend/show"
end
end
end

Answer 2

Thanks a lot for help! I found the bug.
The routing error was caused by the following line of the layout html file
<%= auto_discovery_link_tag(:rss, {:action => "index"}, {:title => "RSS"}) %>
I was looking for errors in the erb view files but I forgot about the layout.
I must remember to check the entire view layer in such situations.