Zeitwerk

config/application.rb

@@ -96,6 +96,11 @@ class Application < Rails::Application
 
     config.autoload_paths += config.eager_load_paths
 
+    config.autoloader = :zeitwerk
+
+    # config.load_defaults 6.1
+    # Disable defaults as ActiveRecord::Base.belongs_to_required_by_default = true causes MiqRegion.seed to fail validation on belongs_to maintenance zone
+
     # NOTE:  If you are going to make changes to autoload_paths, please make
     # sure they are all strings.  Rails will push these paths into the
     # $LOAD_PATH.
@@ -159,6 +164,15 @@ class Application < Rails::Application
       Vmdb::Loggers.apply_config(::Settings.log)
     end
 
+    initializer :eager_load_all_the_things, :after => :load_config_initializers do
+      if ENV['DEBUG_MANAGEIQ_ZEITWERK'].present?
+        config.eager_load_paths += config.autoload_paths
+        Vmdb::Plugins.each do |plugin|
+          plugin.config.eager_load_paths += plugin.config.autoload_paths
+        end
+      end
+    end
+
     config.after_initialize do
       Vmdb::Initializer.init
       ActiveRecord::Base.connection_pool.release_connection

config/initializers/yaml_autoloader.rb

@@ -7,6 +7,9 @@
 #
 # Note, this is used to autoload constants serialized as yaml from one process and loaded in another such as through
 # args in the MiqQueue. An alternative would be to eager load all of our autoload_paths in all processes.
+#
+# This is still needed in some areas for zeitwerk, such as YAML files for tests in the manageiq-providers-vmware
+# that reference a constant: RbVmomi::VIM::TaskEvent
 Psych::Visitors::ToRuby.prepend Module.new {
   def resolve_class(klass_name)
     (class_loader.class != Psych::ClassLoader::Restricted && klass_name && klass_name.safe_constantize) || super

config/initializers/zeitwerk.rb

@@ -0,0 +1,19 @@
+if Rails.application.config.autoloader == :zeitwerk && Rails.autoloaders.main
+  if ENV['DEBUG_MANAGEIQ_ZEITWERK'].present?
+    Zeitwerk::Loader.default_logger = method(:puts)
+    Rails.autoloaders.main.logger = Logger.new($stdout)
+  end
+
+  # These specific directories are for code organization, not namespacing:
+  # TODO: these should be either renamed with good names, the intermediate directory removed
+  # and/or both.
+  Rails.autoloaders.main.collapse(Rails.root.join("lib/manageiq/reporting/charting"))
+  Rails.autoloaders.main.collapse(Rails.root.join("lib/ansible/runner/credential"))
+  Rails.autoloaders.main.collapse(Rails.root.join("lib/pdf_generator"))
+
+  # requires qpid, which is an optional dependency because LOL mac
+  if RUBY_PLATFORM.include?("darwin")
+    message_handler_path = Pathname.new(Vmdb::Plugins.paths[ManageIQ::Providers::Nuage::Engine]).join("app/models/manageiq/providers/nuage/network_manager/event_catcher/messaging_handler.rb")
+    Rails.autoloaders.main.ignore(message_handler_path)
+  end
+end

spec/initializers/yaml_autoloader_spec.rb

@@ -6,6 +6,7 @@
   let(:missing_model)   { model_directory.join("zzz_model.rb") }
 
   before do
+    skip "This is currently not testable with zeitwerk!" if Rails.application.config.autoloader == :zeitwerk
     File.write(missing_model, "class ZzzModel\nend\n")
     ActiveSupport::Dependencies.autoload_paths << model_directory
   end