Zeitwerk and Modules Nested in Classes

Question

I'm having some trouble switching from the classic autoloader to Zeitwerk with a Rails app that's seen the light of day back in Rails 3 days – so there's some crust there.

Some model code has been extracted to modules and these modules are nested in the model class (which acts as the namespace):

# app/models/donation
class Donation < ApplicationRecord
  (...)
end

# app/models/donation/download
class Donation
  module Download
    def csv
      (...)
    end
  end
end

The modules are then used on the fly when needed:

donation = Donation.find(...)
donation.extend(Donation::Download).csv

Since the subdirs in app/models are not added by default, it's done explicitly in application.rb:

Dir[
  "#{config.root}/app/models/*/"
].then do |paths|
  config.autoload_paths += paths
  config.eager_load_paths += paths
end

The eager_load_paths are required by Zeitwerk (as per the Rails guides), however, Zeitwerk doesn't seem to like this constellation:

% rails zeitwerk:check
Hold on, I am eager loading the application.
expected file app/models/donation/download.rb to define constant Download

Strange, because Download is defined there. Any idea what's going on here and how best to refactor things to work with Zeitwerk?

Thanks for your hints!

Answer 1

Hmmm, that should work out of the box, looks like a regular setup to me.

Since app/models is in the autoload paths, Donation and Donation::Download are going to be autoloaded just fine, no custom configuration is needed.

If they do not, the app has to be doing something funky. We could debug it.