1 files changed, 99 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/dependencies/zeitwerk_integration.rb b/activesupport/lib/active_support/dependencies/zeitwerk_integration.rb
new file mode 100644
index 0000000000..fd39ad6e55
--- /dev/null
+++ b/activesupport/lib/active_support/dependencies/zeitwerk_integration.rb
@@ -0,0 +1,99 @@
+# frozen_string_literal: true
+
+require "set"
+require "active_support/core_ext/string/inflections"
+
+module ActiveSupport
+  module Dependencies
+    module ZeitwerkIntegration # :nodoc: all
+      module Decorations
+        def clear
+          Dependencies.unload_interlock do
+            Rails.autoloaders.main.reload
+          rescue Zeitwerk::ReloadingDisabledError
+            raise "reloading is disabled because config.cache_classes is true"
+          end
+        end
+
+        def constantize(cpath)
+          ActiveSupport::Inflector.constantize(cpath)
+        end
+
+        def safe_constantize(cpath)
+          ActiveSupport::Inflector.safe_constantize(cpath)
+        end
+
+        def autoloaded_constants
+          Rails.autoloaders.main.unloadable_cpaths
+        end
+
+        def autoloaded?(object)
+          cpath = object.is_a?(Module) ? object.name : object.to_s
+          Rails.autoloaders.main.unloadable_cpath?(cpath)
+        end
+
+        def verbose=(verbose)
+          l = verbose ? logger || Rails.logger : nil
+          Rails.autoloaders.each { |autoloader| autoloader.logger = l }
+        end
+
+        def unhook!
+          :no_op
+        end
+      end
+
+      module Inflector
+        def self.camelize(basename, _abspath)
+          basename.camelize
+        end
+      end
+
+      class << self
+        def take_over(enable_reloading:)
+          setup_autoloaders(enable_reloading)
+          freeze_paths
+          decorate_dependencies
+        end
+
+        private
+
+          def setup_autoloaders(enable_reloading)
+            Dependencies.autoload_paths.each do |autoload_path|
+              # Zeitwerk only accepts existing directories in `push_dir` to
+              # prevent misconfigurations.
+              next unless File.directory?(autoload_path)
+
+              autoloader = \
+                autoload_once?(autoload_path) ? Rails.autoloaders.once : Rails.autoloaders.main
+
+              autoloader.push_dir(autoload_path)
+              autoloader.do_not_eager_load(autoload_path) unless eager_load?(autoload_path)
+            end
+
+            Rails.autoloaders.main.enable_reloading if enable_reloading
+            Rails.autoloaders.each(&:setup)
+          end
+
+          def autoload_once?(autoload_path)
+            Dependencies.autoload_once_paths.include?(autoload_path)
+          end
+
+          def eager_load?(autoload_path)
+            Dependencies._eager_load_paths.member?(autoload_path)
+          end
+
+          def freeze_paths
+            Dependencies.autoload_paths.freeze
+            Dependencies.autoload_once_paths.freeze
+            Dependencies._eager_load_paths.freeze
+          end
+
+          def decorate_dependencies
+            Dependencies.unhook!
+            Dependencies.singleton_class.prepend(Decorations)
+            Object.class_eval { alias_method :require_dependency, :require }
+          end
+      end
+    end
+  end
+end