Rails routes: Order of nested scopes - ruby-on-rails

Question

so I have a route that is a bit more complex and I have an issue with the order of two nested scopes. Their order seems to be reversed. I want the most inner scope to be the last segment of the URL before the action. But it is the first.
routes.rb
namespace :customer do
namespace :api do
resources :products, only: [], param: :uid do
scope module: 'products' do
scope :buyer do
post :set_to_waiting_list, to: 'buyers#set_to_waiting_list'
end
end
end
end
end
Controller:
module Customer
module Api
module Products
class BuyersController < Customer::ApiController
def set_to_waiting_list
# do stuff
end
end
end
end
end
This gives me this route when running rake routes:
customer_api_product_set_to_waiting_list POST /customer/api/buyer/products/:product_uid/set_to_waiting_list(.:format) customer/api/products/buyers#set_to_waiting_list
But the URL I'm actually looking for is:
POST /customer/api/products/:product_uid/buyer/set_to_waiting_list
Reason is that this modifies the buyer and not the product. Also the buyer is fetched via the product uid (plus logged in user), so this URL format makes much more sense.
I don't really understand

Answer 1

I'm still interested in the logic behind this. But for anyone looking for an solution, I just solved it with:
namespace :customer do
namespace :api do
resources :products, only: [], param: :uid do
scope module: 'products' do
post :set_to_waiting_list, path: 'buyer/set_to_waiting_list' to: 'buyers#set_to_waiting_list'
end
end
end
end

Answer 2

You need to add a nested block so that the scope knows where to place the path prefix:
namespace :customer do
namespace :api do
scope module: 'products' do
resources :products, only: [], param: :uid do
nested do
scope :buyer do
post :set_to_waiting_list, to: 'buyers#set_to_waiting_list'
end
end
end
end
end
end
nested is not documented, so I'm not sure if you should rely on this. As an alternative, you can add a resource :buyers, only: [] {} wrapper:
namespace :customer do
namespace :api do
scope module: 'products' do
resources :products, only: [], param: :uid do
resource :buyer, only: [] do
collection do
post :set_to_waiting_list
end
end
end
end
end
end
The route and controller are the same in both cases, but the URL helper is different:
customer_api_product_set_to_waiting_list
POST /customer/api/products/:product_uid/buyer/set_to_waiting_list(.:format)
customer/api/products/buyers#set_to_waiting_list
vs
set_to_waiting_list_customer_api_product_buyer
POST /customer/api/products/:product_uid/buyer/set_to_waiting_list(.:format)
customer/api/products/buyers#set_to_waiting_list
Source: https://github.com/rails/rails/issues/12626