`add_route': path is required (ArgumentError)

Question

This error happens when I try to restart my server with "rails s". It looks like a problem in routes.rb, which I've looked at, but don't see anything amiss and I haven't changed routes.rb for several commits. I can't find anything on this error anywhere. I could use a tip on where to look next for a cause. I'm sorry the following isn't formatted better:

 /Users/ianyoung/.rvm/gems/ruby-2.1.1/gems/actionpack-4.2.3/lib/action_dispatch/routing/mapper.rb:1543:in
 `add_route': path is required (ArgumentError) from
 /Users/ianyoung/.rvm/gems/ruby-2.1.1/gems/actionpack-4.2.3/lib/action_dispatch/routing/mapper.rb:1536:in
 `decomposed_match'from
 /Users/ianyoung/.rvm/gems/ruby-2.1.1/gems/actionpack-4.2.3/lib/action_dispatch/routing/mapper.rb:1517:in
 `block in match'

Running rake routes gives me a similar error:

 rake aborted! ArgumentError: path is required
 /Users/ianyoung/.rvm/gems/ruby-2.1.1/gems/actionpack-4.2.3/lib/action_dispatch/routing/mapper.rb:1543:in
 `add_route'
 /Users/ianyoung/.rvm/gems/ruby-2.1.1/gems/actionpack-4.2.3/lib/action_dispatch/routing/mapper.rb:1536:in
 `decomposed_match'

To try to find the error in routes.rb I've removed parts/all of the content of that file except the opening block (below) and the error persists:

Rails.application.routes.draw do
end

Thank you.

Answer 1

git diff helped me figure it out. I'd extended class String in config/initializers with a string instance method called blank?. Rails didn't like that.