Zeitwerk integration

8 files changed, 225 insertions, 42 deletions

diff --git a/railties/test/application/configuration_test.rb b/railties/test/application/configuration_test.rb
index 9ea4d6dc5f..960f708bdf 100644
--- a/railties/test/application/configuration_test.rb
+++ b/railties/test/application/configuration_test.rb
@@ -1157,6 +1157,27 @@ module ApplicationTests
       end
     end
 
+    test "autoloader & autoloader=" do
+      app "development"
+
+      config = Rails.application.config
+      assert_instance_of Zeitwerk::Loader, Rails.autoloader
+      assert_instance_of Zeitwerk::Loader, Rails.once_autoloader
+      assert_equal [Rails.autoloader, Rails.once_autoloader], Rails.autoloaders
+
+      config.autoloader = :classic
+      assert_nil Rails.autoloader
+      assert_nil Rails.once_autoloader
+      assert_empty Rails.autoloaders
+
+      config.autoloader = :zeitwerk
+      assert_instance_of Zeitwerk::Loader, Rails.autoloader
+      assert_instance_of Zeitwerk::Loader, Rails.once_autoloader
+      assert_equal [Rails.autoloader, Rails.once_autoloader], Rails.autoloaders
+
+      assert_raises(ArgumentError) { config.autoloader = :unknown }
+    end
+
     test "config.action_view.cache_template_loading with cache_classes default" do
       add_to_config "config.cache_classes = true"
 
diff --git a/railties/test/application/mailer_previews_test.rb b/railties/test/application/mailer_previews_test.rb
index ba186bda44..fb84276b8a 100644
--- a/railties/test/application/mailer_previews_test.rb
+++ b/railties/test/application/mailer_previews_test.rb
@@ -85,6 +85,7 @@ module ApplicationTests
     end
 
     test "mailer previews are loaded from a custom preview_path" do
+      app_dir "lib/mailer_previews"
       add_to_config "config.action_mailer.preview_path = '#{app_path}/lib/mailer_previews'"
 
       mailer "notifier", <<-RUBY
@@ -254,6 +255,7 @@ module ApplicationTests
     end
 
     test "mailer previews are reloaded from a custom preview_path" do
+      app_dir "lib/mailer_previews"
       add_to_config "config.action_mailer.preview_path = '#{app_path}/lib/mailer_previews'"
 
       app("development")
@@ -818,6 +820,7 @@ module ApplicationTests
       def build_app
         super
         app_file "config/routes.rb", "Rails.application.routes.draw do; end"
+        app_dir "test/mailers/previews"
       end
 
       def mailer(name, contents)
diff --git a/railties/test/application/multiple_applications_test.rb b/railties/test/application/multiple_applications_test.rb
index 432344bccc..f0f1112f6b 100644
--- a/railties/test/application/multiple_applications_test.rb
+++ b/railties/test/application/multiple_applications_test.rb
@@ -100,30 +100,6 @@ module ApplicationTests
       assert_nothing_raised { AppTemplate::Application.new }
     end
 
-    def test_initializers_run_on_different_applications_go_to_the_same_class
-      application1 = AppTemplate::Application.new
-      run_count = 0
-
-      AppTemplate::Application.initializer :init0 do
-        run_count += 1
-      end
-
-      application1.initializer :init1 do
-        run_count += 1
-      end
-
-      AppTemplate::Application.new.initializer :init2 do
-        run_count += 1
-      end
-
-      assert_equal 0, run_count, "Without loading the initializers, the count should be 0"
-
-      # Set config.eager_load to false so that an eager_load warning doesn't pop up
-      AppTemplate::Application.create { config.eager_load = false }.initialize!
-
-      assert_equal 3, run_count, "There should have been three initializers that incremented the count"
-    end
-
     def test_consoles_run_on_different_applications_go_to_the_same_class
       run_count = 0
       AppTemplate::Application.console { run_count += 1 }
diff --git a/railties/test/application/rake_test.rb b/railties/test/application/rake_test.rb
index 44e3b0f66b..fe56e3d076 100644
--- a/railties/test/application/rake_test.rb
+++ b/railties/test/application/rake_test.rb
@@ -145,8 +145,8 @@ module ApplicationTests
       # loading a specific fixture
       rails "db:fixtures:load", "FIXTURES=products"
 
-      assert_equal 2, ::AppTemplate::Application::Product.count
-      assert_equal 0, ::AppTemplate::Application::User.count
+      assert_equal 2, Product.count
+      assert_equal 0, User.count
     end
 
     def test_loading_only_yml_fixtures
diff --git a/railties/test/application/zeitwerk_integration_test.rb b/railties/test/application/zeitwerk_integration_test.rb
new file mode 100644
index 0000000000..d44b7f7e4d
--- /dev/null
+++ b/railties/test/application/zeitwerk_integration_test.rb
@@ -0,0 +1,164 @@
+# 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_instance_of Zeitwerk::Loader, Rails.autoloader
+    assert_instance_of Zeitwerk::Loader, Rails.once_autoloader
+    assert_equal [Rails.autoloader, Rails.once_autoloader], Rails.autoloaders
+  end
+
+  test "ActiveSupport::Dependencies is not decorated in classic mode" do
+    add_to_config 'config.autoloader = :classic'
+    boot
+
+    assert_not decorated?
+    assert_nil Rails.autoloader
+    assert_nil Rails.once_autoloader
+    assert_empty Rails.autoloaders
+  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 "autoloaded_constants returns autoloaded constant paths" do
+    app_file "app/models/admin/user.rb", "class Admin::User; end"
+    app_file "app/models/post.rb", "class Post; end"
+    boot
+
+    assert Admin::User
+    assert_equal ["Admin", "Admin::User"], deps.autoloaded_constants
+  end
+
+  test "autoloaded? says if a constant has been autoloaded" 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")
+  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 "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 paths that are below Gem.path go to the once autoloader" do
+    app_dir "extras"
+    add_to_config 'config.autoload_paths << "#{Rails.root}/extras"'
+
+    # Mocks Gem.path to include the extras directory.
+    Gem.singleton_class.prepend(
+      Module.new do
+        def path
+          super + ["#{Rails.root}/extras"]
+        end
+      end
+    )
+    boot
+
+    refute_includes Rails.autoloader.dirs, "#{app_path}/extras"
+    assert_includes Rails.once_autoloader.dirs, "#{app_path}/extras"
+  end
+
+  test "clear reloads the main autoloader, and does not reload the once one" do
+    boot
+
+    $zeitwerk_integration_reload_test = []
+
+    autoloader = Rails.autoloader
+    def autoloader.reload
+      $zeitwerk_integration_reload_test << :autoloader
+      super
+    end
+
+    once_autoloader = Rails.once_autoloader
+    def once_autoloader.reload
+      $zeitwerk_integration_reload_test << :once_autoloader
+      super
+    end
+
+    ActiveSupport::Dependencies.clear
+
+    assert_equal %i(autoloader), $zeitwerk_integration_reload_test
+  end
+end
diff --git a/railties/test/generators/app_generator_test.rb b/railties/test/generators/app_generator_test.rb
index 1ee9e43e89..937b8eb427 100644
--- a/railties/test/generators/app_generator_test.rb
+++ b/railties/test/generators/app_generator_test.rb
@@ -660,6 +660,15 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_gem "jbuilder"
   end
 
+  def test_inclusion_of_zeitwerk
+    run_generator
+    if RUBY_ENGINE == "ruby"
+      assert_gem "zeitwerk"
+    else
+      assert_no_gem "zeitwerk"
+    end
+  end
+
   def test_inclusion_of_a_debugger
     run_generator
     if defined?(JRUBY_VERSION) || RUBY_ENGINE == "rbx"
diff --git a/railties/test/isolation/abstract_unit.rb b/railties/test/isolation/abstract_unit.rb
index 0e8e0e86ee..47d42645c6 100644
--- a/railties/test/isolation/abstract_unit.rb
+++ b/railties/test/isolation/abstract_unit.rb
@@ -421,6 +421,10 @@ module TestHelpers
       file_name
     end
 
+    def app_dir(path)
+      FileUtils.mkdir_p("#{app_path}/#{path}")
+    end
+
     def remove_file(path)
       FileUtils.rm_rf "#{app_path}/#{path}"
     end
@@ -487,7 +491,11 @@ Module.new do
   # Fake 'Bundler.require' -- we run using the repo's Gemfile, not an
   # app-specific one: we don't want to require every gem that lists.
   contents = File.read("#{app_template_path}/config/application.rb")
-  contents.sub!(/^Bundler\.require.*/, "%w(turbolinks webpacker).each { |r| require r }")
+  if RUBY_ENGINE == "ruby"
+    contents.sub!(/^Bundler\.require.*/, "%w(turbolinks webpacker zeitwerk).each { |r| require r }")
+  else
+    contents.sub!(/^Bundler\.require.*/, "%w(turbolinks webpacker).each { |r| require r }")
+  end
   File.write("#{app_template_path}/config/application.rb", contents)
 
   require "rails"
diff --git a/railties/test/railties/engine_test.rb b/railties/test/railties/engine_test.rb
index 851407dede..69f6e34d58 100644
--- a/railties/test/railties/engine_test.rb
+++ b/railties/test/railties/engine_test.rb
@@ -704,25 +704,27 @@ YAML
       RUBY
 
       @plugin.write "app/controllers/bukkits/foo_controller.rb", <<-RUBY
-        class Bukkits::FooController < ActionController::Base
-          def index
-            render inline: "<%= help_the_engine %>"
-          end
+        module Bukkits
+          class FooController < ActionController::Base
+            def index
+              render inline: "<%= help_the_engine %>"
+            end
 
-          def show
-            render plain: foo_path
-          end
+            def show
+              render plain: foo_path
+            end
 
-          def from_app
-            render inline: "<%= (self.respond_to?(:bar_path) || self.respond_to?(:something)) %>"
-          end
+            def from_app
+              render inline: "<%= (self.respond_to?(:bar_path) || self.respond_to?(:something)) %>"
+            end
 
-          def routes_helpers_in_view
-            render inline: "<%= foo_path %>, <%= main_app.bar_path %>"
-          end
+            def routes_helpers_in_view
+              render inline: "<%= foo_path %>, <%= main_app.bar_path %>"
+            end
 
-          def polymorphic_path_without_namespace
-            render plain: polymorphic_path(Post.new)
+            def polymorphic_path_without_namespace
+              render plain: polymorphic_path(Post.new)
+            end
           end
         end
       RUBY