Doorkeeper: DEPRECATION WARNING: Initialization autoloaded the constants CustomTokenResponse and CustomTokenErrorResponse.

[ahaverty]

Steps to reproduce

Following the guide on custom token responses, Rails now gives me deprecation warnings about the two constants that I setup. https://github.com/doorkeeper-gem/doorkeeper/wiki/Customizing-Token-Response
The guide works, and my custom responses are working.
But on running rspec, I'm seeing this:

alan$ rspec ./spec/requests/api/v1/passwords_controller_spec.rb
DEPRECATION WARNING: Initialization autoloaded the constants CustomTokenResponse and CustomTokenErrorResponse.

Being able to do this is deprecated. Autoloading during initialization is going
to be an error condition in future versions of Rails.

Reloading does not reboot the application, and therefore code executed during
initialization does not run again. So, if you reload CustomTokenResponse, for example,
the expected changes won't be reflected in that stale Module object.

These autoloaded constants have been unloaded.

Please, check the "Autoloading and Reloading Constants" guide for solutions.
 (called from <top (required)> at /Users/alan/projects/twinlite-web/config/environment.rb:5)
...

Finished in 5.15 seconds (files took 4.69 seconds to load)
3 examples, 0 failures

Expected behavior

No deprecation warnings

Actual behavior

See reproduction steps☝️

System configuration

Standard ruby/rails app, with devise and doorkeeper for our api endpoints.

Doorkeeper initializer:

# config/initializers/doorkeeper.rb
Doorkeeper.configure do
  orm :active_record
  resource_owner_from_credentials do |routes|
    base_user = BaseUser.find_for_database_authentication(email: params[:email])
    if base_user&.valid_for_authentication? { base_user.valid_password?(params[:password]) }
      base_user
    end
  end
  api_only
  use_refresh_token
  grant_flows %w(password)
  skip_authorization { true }
end

Doorkeeper::OAuth::TokenResponse.send :prepend, CustomTokenResponse
Doorkeeper::OAuth::ErrorResponse.send :prepend, CustomTokenErrorResponse

Ruby version: 2.5.0

Gemfile.lock:

Gemfile.lock content

GEM
  remote: https://rubygems.org/
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PLATFORMS
  ruby

DEPENDENCIES
  allowable (~> 1.1.0)
  aws-sdk-s3
  better_errors
  binding_of_caller
  bootsnap (>= 1.4.5)
  bootstrap-email
  bullet (~> 6.0.2)
  byebug
  capybara (~> 3.29.0)
  capybara-screenshot (~> 1.0.23)
  cocoon (~> 1.2.14)
  database_cleaner (~> 1.7.0)
  devise (~> 4.7.1)
  devise_invitable (~> 2.0.1)
  doorkeeper (~> 5.2.2)
  dropybara (~> 1.0.0)
  factory_bot_rails (~> 5.0.2)
  faker (~> 2.3.0)
  figaro (~> 1.1.1)
  friendly_id (~> 5.2.5)
  hellosign-ruby-sdk (~> 3.7.7)
  honeybadger (~> 4.5)
  image_processing (~> 1.9.3)
  jbuilder (~> 2.9.1)
  jquery-rails (~> 4.3.5)
  kaminari (~> 1.1.1)
  letter_opener (~> 1.7.0)
  listen (>= 3.1.5, < 3.2)
  mini_magick (~> 4.9.5)
  money-rails (~> 1.13.2)
  pg (>= 0.18, < 2.0)
  phone (~> 1.2.3)
  poltergeist (~> 1.18.1)
  pry (~> 0.12.2)
  puma (~> 4.1.1)
  rails (~> 6.0.0)
  rails-controller-testing (~> 1.0.4)
  rspec (~> 3.8.0)
  rspec-rails (~> 4.0.0.beta2)
  rspec-retry (~> 0.6.1)
  rubocop (~> 0.74.0)
  rubocop-performance (~> 1.4.1)
  rubocop-rails (~> 2.3.2)
  sass-rails (~> 6.0.0)
  scenic (~> 1.5.1)
  selenium-webdriver (~> 3.142.6)
  shoulda-matchers (~> 4.1.2)
  sidekiq (~> 6.0.0)
  simplecov (~> 0.17.1)
  slack-notifier
  spring (~> 2.1.0)
  spring-watcher-listen (~> 2.0.1)
  timecop (~> 0.9.1)
  turbolinks (~> 5.2.0)
  warden (~> 1.2.8)
  web-console (>= 4.0.1)
  webdrivers (~> 4.1.2)
  webpacker (~> 4.0.7)

RUBY VERSION
   ruby 2.5.0p0

BUNDLED WITH
   2.0.2

[nbulaj]

It's because with Rails 6 it uses Zeitwerk and initielizers calls your custom classes which wasn't loaded yet. You need to configure Zeitwerk somehow, I can't give you an answer right now on how to do it

[jasl]

could you try remove config.autoload_paths << "#{Rails.root}/lib"? and in your custom classes, don't do any require

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[tgrushkasm]

I found that wrapping some constant calls in a to_prepare block in doorkeeper.rb initializer silences this warning (using the example above):

Rails.application.config.to_prepare do
  Doorkeeper::OAuth::TokenResponse.send :prepend, CustomTokenResponse
  Doorkeeper::OAuth::ErrorResponse.send :prepend, CustomTokenErrorResponse
end

This is documented in an article: https://www.danott.co/today-i-learned/2019-10-16/
And a Rails issue: https://github.com/rails/rails/issues/36363