title: Unable to autoload constant API Controller in Rails 4
body: <p>I'm creating a simple api endpoint in my Rails 4.2.6 app but am having problems with it.</p>
  
  <p>When I hit the url: <a href="http://lvh.me:9077/api/v1/grubs" rel="noreferrer">http://lvh.me:9077/api/v1/grubs</a> I receive the following error:</p>
  
  <pre><code>Unable to autoload constant Api::V1::GrubsController, expected /Users/shakycode/code/grubs/app/controllers/api/v1/grubs_controller.rb to define it
  </code></pre>
  
  <p>Here is my routes.rb file defining the endpoint.</p>
  
  <pre><code>namespace :api do
      namespace :v1 do
        resources :grubs, only: [:index]
      end
    end
  </code></pre>
  
  <p>Here is my app/controllers/api/v1/grubs_controller.rb</p>
  
  <pre><code>class API::V1::GrubsController &lt; ApplicationController
     protect_from_forgery with: :null_session
     before_action :destroy_session
  
   def destroy_session
     request.session_options[:skip] = true
   end
  
    def index
      @grubs = Grub.all
      respond_to do |format|
        format.json { render json: @grubs}
      end
    end
  end
  </code></pre>
  
  <p>I have a Rails 4.2.1 app where I used the same strategy, but in 4.2.6 I'm having this error occur when I try to pull against the API.</p>
  
  <p>Thanks in advance!</p>
  
  <p>Update: Here's the exception that is raised using better_errors in the browser:</p>
  
  <pre><code>load_missing_constantactivesupport (4.2.6) lib/active_support/dependencies.rb
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          if loading.include?(expanded)
            raise "Circular dependency detected while autoloading constant #{qualified_name}"
          else
            require_or_load(expanded, qualified_name)
            raise LoadError, "Unable to autoload constant #{qualified_name}, expected #{file_path} to define it" unless from_mod.const_defined?(const_name, false)
            return from_mod.const_get(const_name)
          end
        elsif mod = autoload_module!(from_mod, const_name, qualified_name, path_suffix)
          return mod
        elsif (parent = from_mod.parent) &amp;&amp; parent != from_mod &amp;&amp;
  </code></pre>