title: Rails 6 not auto-loading class properly in development (zeitwerk mode)
body: <p>My understanding is that Rails is able to auto-load classes properly named within the <code>app</code> folder, by default.</p>
  <p>It's not happening for me, so I want to see if you can find an obvious issue with my code.</p>
  <p>My folders/files:</p>
  <pre><code>app
     blueprints
        concerns
           ingredient_blueprint_concern.rb
        liqueur_blueprint.rb
     controllers
     models
     ...
  </code></pre>
  <pre class="lang-rb prettyprint-override"><code>#app/blueprints/concerns/ingredient_blueprint_concern.rb
  
  module Concerns
    module IngredientBlueprintConcern
      extend ActiveSupport::Concern
  
      included do
        attributes :name
      end
    end
  end
  
  </code></pre>
  <pre class="lang-rb prettyprint-override"><code># app/blueprints/liqueur_blueprint.rb
  
  class LiqueurBlueprint &lt; BaseBlueprint
    include ::Concerns::IngredientBlueprintConcern
  
    # ...
  end
  
  </code></pre>
  <p>rails console:</p>
  <pre><code>&gt; Concerns
  =&gt; NameError (uninitialized constant Concerns
     Did you mean?  Concurrent):
  </code></pre>
  <hr />
  <p>It seems related to the new Rails 6 <strong>zeitwerk</strong> mode. If I go back the the <strong>classic</strong> mode (with the code below), it seems to work fine:</p>
  <pre><code># application.rb
  config.autoloader = :classic
  </code></pre>