1 files changed, 350 insertions, 0 deletions
diff --git a/railties/test/application/zeitwerk_integration_test.rb b/railties/test/application/zeitwerk_integration_test.rb
new file mode 100644
index 0000000000..9146222f73
--- /dev/null
+++ b/railties/test/application/zeitwerk_integration_test.rb
@@ -0,0 +1,350 @@
+# frozen_string_literal: true
+
+require "isolation/abstract_unit"
+require "active_support/dependencies/zeitwerk_integration"
+
+class ZeitwerkIntegrationTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::Isolation
+
+  def setup
+    build_app
+  end
+
+  def boot(env = "development")
+    app(env)
+  end
+
+  def teardown
+    teardown_app
+  end
+
+  def deps
+    ActiveSupport::Dependencies
+  end
+
+  def decorated?
+    deps.singleton_class < deps::ZeitwerkIntegration::Decorations
+  end
+
+  test "ActiveSupport::Dependencies is decorated by default" do
+    boot
+
+    assert decorated?
+    assert Rails.autoloaders.zeitwerk_enabled?
+    assert_instance_of Zeitwerk::Loader, Rails.autoloaders.main
+    assert_instance_of Zeitwerk::Loader, Rails.autoloaders.once
+    assert_equal [Rails.autoloaders.main, Rails.autoloaders.once], Rails.autoloaders.to_a
+  end
+
+  test "ActiveSupport::Dependencies is not decorated in classic mode" do
+    add_to_config "config.autoloader = :classic"
+    boot
+
+    assert_not decorated?
+    assert_not Rails.autoloaders.zeitwerk_enabled?
+    assert_nil Rails.autoloaders.main
+    assert_nil Rails.autoloaders.once
+    assert_equal 0, Rails.autoloaders.count
+  end
+
+  test "autoloaders inflect with Active Support" do
+    app_file "config/initializers/inflections.rb", <<-RUBY
+      ActiveSupport::Inflector.inflections(:en) do |inflect|
+        inflect.acronym 'RESTful'
+      end
+    RUBY
+
+    app_file "app/controllers/restful_controller.rb", <<-RUBY
+      class RESTfulController < ApplicationController
+      end
+    RUBY
+
+    boot
+
+    basename  = "restful_controller"
+    abspath   = "#{Rails.root}/app/controllers/#{basename}.rb"
+    camelized = "RESTfulController"
+
+    Rails.autoloaders.each do |autoloader|
+      assert_equal camelized, autoloader.inflector.camelize(basename, abspath)
+    end
+
+    assert RESTfulController
+  end
+
+  test "constantize returns the value stored in the constant" do
+    app_file "app/models/admin/user.rb", "class Admin::User; end"
+    boot
+
+    assert_same Admin::User, deps.constantize("Admin::User")
+  end
+
+  test "constantize raises if the constant is unknown" do
+    boot
+
+    assert_raises(NameError) { deps.constantize("Admin") }
+  end
+
+  test "safe_constantize returns the value stored in the constant" do
+    app_file "app/models/admin/user.rb", "class Admin::User; end"
+    boot
+
+    assert_same Admin::User, deps.safe_constantize("Admin::User")
+  end
+
+  test "safe_constantize returns nil for unknown constants" do
+    boot
+
+    assert_nil deps.safe_constantize("Admin")
+  end
+
+  test "unloadable constants (main)" do
+    app_file "app/models/user.rb", "class User; end"
+    app_file "app/models/post.rb", "class Post; end"
+    boot
+
+    assert Post
+
+    assert deps.autoloaded?("Post")
+    assert deps.autoloaded?(Post)
+    assert_not deps.autoloaded?("User")
+
+    assert_equal ["Post"], deps.autoloaded_constants
+  end
+
+  test "unloadable constants (once)" do
+    add_to_config 'config.autoload_once_paths << "#{Rails.root}/extras"'
+    app_file "extras/foo.rb", "class Foo; end"
+    app_file "extras/bar.rb", "class Bar; end"
+    boot
+
+    assert Foo
+
+    assert_not deps.autoloaded?("Foo")
+    assert_not deps.autoloaded?(Foo)
+    assert_not deps.autoloaded?("Bar")
+
+    assert_empty deps.autoloaded_constants
+  end
+
+  test "unloadable constants (reloading disabled)" do
+    app_file "app/models/user.rb", "class User; end"
+    app_file "app/models/post.rb", "class Post; end"
+    boot("production")
+
+    assert Post
+
+    assert_not deps.autoloaded?("Post")
+    assert_not deps.autoloaded?(Post)
+    assert_not deps.autoloaded?("User")
+
+    assert_empty deps.autoloaded_constants
+  end
+
+  test "eager loading loads the application code" do
+    $zeitwerk_integration_test_user = false
+    $zeitwerk_integration_test_post = false
+
+    app_file "app/models/user.rb", "class User; end; $zeitwerk_integration_test_user = true"
+    app_file "app/models/post.rb", "class Post; end; $zeitwerk_integration_test_post = true"
+
+    boot("production")
+
+    assert $zeitwerk_integration_test_user
+    assert $zeitwerk_integration_test_post
+  end
+
+  test "reloading is enabled if config.cache_classes is false" do
+    boot
+
+    assert     Rails.autoloaders.main.reloading_enabled?
+    assert_not Rails.autoloaders.once.reloading_enabled?
+  end
+
+  test "reloading is disabled if config.cache_classes is true" do
+    boot("production")
+
+    assert_not Rails.autoloaders.main.reloading_enabled?
+    assert_not Rails.autoloaders.once.reloading_enabled?
+  end
+
+  test "reloading raises if config.cache_classes is true" do
+    boot("production")
+
+    e = assert_raises(StandardError) do
+      deps.clear
+    end
+    assert_equal "reloading is disabled because config.cache_classes is true", e.message
+  end
+
+  test "eager loading loads code in engines" do
+    $test_blog_engine_eager_loaded = false
+
+    engine("blog") do |bukkit|
+      bukkit.write("lib/blog.rb", "class BlogEngine < Rails::Engine; end")
+      bukkit.write("app/models/post.rb", "Post = $test_blog_engine_eager_loaded = true")
+    end
+
+    boot("production")
+
+    assert $test_blog_engine_eager_loaded
+  end
+
+  test "eager loading loads anything managed by Zeitwerk" do
+    $zeitwerk_integration_test_user = false
+    app_file "app/models/user.rb", "class User; end; $zeitwerk_integration_test_user = true"
+
+    $zeitwerk_integration_test_extras = false
+    app_dir "extras"
+    app_file "extras/webhook_hacks.rb", "WebhookHacks = 1; $zeitwerk_integration_test_extras = true"
+
+    require "zeitwerk"
+    autoloader = Zeitwerk::Loader.new
+    autoloader.push_dir("#{app_path}/extras")
+    autoloader.setup
+
+    boot("production")
+
+    assert $zeitwerk_integration_test_user
+    assert $zeitwerk_integration_test_extras
+  end
+
+  test "autoload directories not present in eager load paths are not eager loaded" do
+    $zeitwerk_integration_test_user = false
+    app_file "app/models/user.rb", "class User; end; $zeitwerk_integration_test_user = true"
+
+    $zeitwerk_integration_test_lib = false
+    app_dir "lib"
+    app_file "lib/webhook_hacks.rb", "WebhookHacks = 1; $zeitwerk_integration_test_lib = true"
+
+    $zeitwerk_integration_test_extras = false
+    app_dir "extras"
+    app_file "extras/websocket_hacks.rb", "WebsocketHacks = 1; $zeitwerk_integration_test_extras = true"
+
+    add_to_config "config.autoload_paths      << '#{app_path}/lib'"
+    add_to_config "config.autoload_once_paths << '#{app_path}/extras'"
+
+    boot("production")
+
+    assert $zeitwerk_integration_test_user
+    assert_not $zeitwerk_integration_test_lib
+    assert_not $zeitwerk_integration_test_extras
+
+    assert WebhookHacks
+    assert WebsocketHacks
+
+    assert $zeitwerk_integration_test_lib
+    assert $zeitwerk_integration_test_extras
+  end
+
+  test "autoload_paths are set as root dirs of main, and in the same order" do
+    boot
+
+    existing_autoload_paths = deps.autoload_paths.select { |dir| File.directory?(dir) }
+    assert_equal existing_autoload_paths, Rails.autoloaders.main.dirs
+  end
+
+  test "autoload_once_paths go to the once autoloader, and in the same order" do
+    extras = %w(e1 e2 e3)
+    extras.each do |extra|
+      app_dir extra
+      add_to_config %(config.autoload_once_paths << "\#{Rails.root}/#{extra}")
+    end
+
+    boot
+
+    extras = extras.map { |extra| "#{app_path}/#{extra}" }
+    extras.each do |extra|
+      assert_not_includes Rails.autoloaders.main.dirs, extra
+    end
+    assert_equal extras, Rails.autoloaders.once.dirs
+  end
+
+  test "clear reloads the main autoloader, and does not reload the once one" do
+    boot
+
+    $zeitwerk_integration_reload_test = []
+
+    main_autoloader = Rails.autoloaders.main
+    def main_autoloader.reload
+      $zeitwerk_integration_reload_test << :main_autoloader
+      super
+    end
+
+    once_autoloader = Rails.autoloaders.once
+    def once_autoloader.reload
+      $zeitwerk_integration_reload_test << :once_autoloader
+      super
+    end
+
+    ActiveSupport::Dependencies.clear
+
+    assert_equal %i(main_autoloader), $zeitwerk_integration_reload_test
+  end
+
+  test "verbose = true sets the dependencies logger if present" do
+    boot
+
+    logger = Logger.new(File::NULL)
+    ActiveSupport::Dependencies.logger = logger
+    ActiveSupport::Dependencies.verbose = true
+
+    Rails.autoloaders.each do |autoloader|
+      assert_same logger, autoloader.logger
+    end
+  end
+
+  test "verbose = true sets the Rails logger as fallback" do
+    boot
+
+    ActiveSupport::Dependencies.verbose = true
+
+    Rails.autoloaders.each do |autoloader|
+      assert_same Rails.logger, autoloader.logger
+    end
+  end
+
+  test "verbose = false sets loggers to nil" do
+    boot
+
+    ActiveSupport::Dependencies.verbose = true
+    Rails.autoloaders.each do |autoloader|
+      assert autoloader.logger
+    end
+
+    ActiveSupport::Dependencies.verbose = false
+    Rails.autoloaders.each do |autoloader|
+      assert_nil autoloader.logger
+    end
+  end
+
+  test "unhooks" do
+    boot
+
+    assert_equal Module, Module.method(:const_missing).owner
+    assert_equal :no_op, deps.unhook!
+  end
+
+  test "autoloaders.logger=" do
+    boot
+
+    logger = ->(_msg) { }
+    Rails.autoloaders.logger = logger
+
+    Rails.autoloaders.each do |autoloader|
+      assert_same logger, autoloader.logger
+    end
+
+    Rails.autoloaders.logger = Rails.logger
+
+    Rails.autoloaders.each do |autoloader|
+      assert_same Rails.logger, autoloader.logger
+    end
+
+    Rails.autoloaders.logger = nil
+
+    Rails.autoloaders.each do |autoloader|
+      assert_nil autoloader.logger
+    end
+  end
+end