Enable Zeitwerk autoloader

Configure's Zeitwerk inflections to match current definitions

config/application.rb

@@ -31,6 +31,8 @@ module Gitlab
 
     config.active_record.sqlite3.represent_boolean_as_integer = true
 
+    config.autoloader = :zeitwerk
+
     # Sidekiq uses eager loading, but directories not in the standard Rails
     # directories must be added to the eager load paths:
     # https://github.com/mperham/sidekiq/wiki/FAQ#why-doesnt-sidekiq-autoload-my-rails-application-code

config/environments/development.rb

@@ -42,7 +42,7 @@ Rails.application.configure do
   config.action_mailer.raise_delivery_errors = true
   # Don't make a mess when bootstrapping a development environment
   config.action_mailer.perform_deliveries = (ENV['BOOTSTRAP'] != '1')
-  config.action_mailer.preview_path = 'app/mailers/previews'
+  config.action_mailer.preview_path = Rails.root.join('app', 'mailers', 'previews')
 
   config.eager_load = false
 

config/environments/test.rb

@@ -43,7 +43,7 @@ Rails.application.configure do
   # Print deprecation notices to the stderr
   config.active_support.deprecation = :stderr
 
-  config.eager_load = true
+  config.eager_load = false
 
   config.cache_store = :null_store
 

config/initializers_before_autoloader/002_zeitwerk.rb

+# frozen_string_literal: true
+
+Rails.autoloaders.each do |autoloader|
+  # We need to ignore these since these are non-Ruby files
+  # that do not define Ruby classes / modules
+  autoloader.ignore(Rails.root.join('lib/support'))
+  # Ignore generators since these are loaded manually by Rails
+  autoloader.ignore(Rails.root.join('lib/generators'))
+  autoloader.ignore(Rails.root.join('ee/lib/generators')) if Gitlab.ee?
+  # Mailer previews are also loaded manually by Rails
+  autoloader.ignore(Rails.root.join('app/mailers/previews'))
+  autoloader.ignore(Rails.root.join('ee/app/mailers/previews')) if Gitlab.ee?
+
+  autoloader.inflector.inflect(
+    'api' => 'API',
+    'api_guard' => 'APIGuard',
+    'group_api_compatibility' => 'GroupAPICompatibility',
+    'project_api_compatibility' => 'ProjectAPICompatibility',
+    'cte' => 'CTE',
+    'recursive_cte' => 'RecursiveCTE',
+    'cidr' => 'CIDR',
+    'cli' => 'CLI',
+    'dn' => 'DN',
+    'hmac_token' => 'HMACToken',
+    'html' => 'HTML',
+    'html_parser' => 'HTMLParser',
+    'html_gitlab' => 'HTMLGitlab',
+    'http' => 'HTTP',
+    'http_connection_adapter' => 'HTTPConnectionAdapter',
+    'http_clone_enabled_check' => 'HTTPCloneEnabledCheck',
+    'chunked_io' => 'ChunkedIO',
+    'http_io' => 'HttpIO',
+    'json' => 'JSON',
+    'json_formatter' => 'JSONFormatter',
+    'json_web_token' => 'JSONWebToken',
+    'as_json' => 'AsJSON',
+    'ldap_key' => 'LDAPKey',
+    'mr_note' => 'MRNote',
+    'pdf' => 'PDF',
+    'rsa_token' => 'RSAToken',
+    'san_extension' => 'SANExtension',
+    'sca' => 'SCA',
+    'spdx' => 'SPDX',
+    'sql' => 'SQL',
+    'ssh_key' => 'SSHKey',
+    'ssh_key_with_user' => 'SSHKeyWithUser',
+    'ssh_public_key' => 'SSHPublicKey',
+    'git_push_ssh_proxy' => 'GitPushSSHProxy',
+    'git_user_default_ssh_config_check' => 'GitUserDefaultSSHConfigCheck',
+    'binary_stl' => 'BinarySTL',
+    'text_stl' => 'TextSTL',
+    'svg' => 'SVG',
+    'function_uri' => 'FunctionURI'
+  )
+end