Deletes the classic implementation of require_dependency

activesupport/lib/active_support/dependencies.rb

@@ -17,6 +17,8 @@
 
 module ActiveSupport # :nodoc:
   module Dependencies # :nodoc:
+    require_relative "dependencies/require_dependency"
+
     extend self
 
     UNBOUND_METHOD_MODULE_NAME = Module.instance_method(:name)
@@ -250,37 +252,6 @@ def require_or_load(file_name)
         Dependencies.require_or_load(file_name)
       end
 
-      # :doc:
-
-      # <b>Warning:</b> This method is obsolete in +:zeitwerk+ mode. In
-      # +:zeitwerk+ mode semantics match Ruby's and you do not need to be
-      # defensive with load order. Just refer to classes and modules normally.
-      # If the constant name is dynamic, camelize if needed, and constantize.
-      #
-      # In +:classic+ mode, interprets a file using +mechanism+ and marks its
-      # defined constants as autoloaded. +file_name+ can be either a string or
-      # respond to <tt>to_path</tt>.
-      #
-      # In +:classic+ mode, use this method in code that absolutely needs a
-      # certain constant to be defined at that point. A typical use case is to
-      # make constant name resolution deterministic for constants with the same
-      # relative name in different namespaces whose evaluation would depend on
-      # load order otherwise.
-      #
-      # Engines that do not control the mode in which their parent application
-      # runs should call +require_dependency+ where needed in case the runtime
-      # mode is +:classic+.
-      def require_dependency(file_name, message = "No such file to load -- %s.rb")
-        file_name = file_name.to_path if file_name.respond_to?(:to_path)
-        unless file_name.is_a?(String)
-          raise ArgumentError, "the file name must either be a String or implement #to_path -- you passed #{file_name.inspect}"
-        end
-
-        Dependencies.depend_on(file_name, message)
-      end
-
-      # :nodoc:
-
       def load_dependency(file)
         if Dependencies.load? && Dependencies.constant_watch_stack.watching?
           descs = Dependencies.constant_watch_stack.watching.flatten.uniq

activesupport/lib/active_support/dependencies/require_dependency.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+module ActiveSupport::Dependencies::RequireDependency
+  # <b>Warning:</b> This method is obsolete. The semantics of the autoloader
+  # match Ruby's and you do not need to be defensive with load order anymore.
+  # Just refer to classes and modules normally.
+  #
+  # Engines that do not control the mode in which their parent application runs
+  # should call +require_dependency+ where needed in case the runtime mode is
+  # +:classic+.
+  def require_dependency(filename)
+    filename = filename.to_path if filename.respond_to?(:to_path)
+
+    unless filename.is_a?(String)
+      raise ArgumentError, "the file name must be either a String or implement #to_path -- you passed #{filename.inspect}"
+    end
+
+    if abspath = ActiveSupport::Dependencies.search_for_file(filename)
+      require abspath
+    else
+      require filename
+    end
+  end
+
+  # We could define require_dependency in Object directly, but a module makes
+  # the extension apparent if you list ancestors.
+  Object.prepend(self)
+end

activesupport/test/dependencies_test.rb

@@ -46,10 +46,6 @@ def test_depend_on_message
     assert_equal "No such file to load -- omgwtfbbq.rb", e.message
   end
 
-  def test_missing_dependency_raises_missing_source_file
-    assert_raise(LoadError) { require_dependency("missing_service") }
-  end
-
   def test_smart_name_error_strings
     e = assert_raise NameError do
       Object.module_eval "ImaginaryObject"
@@ -118,4 +114,6 @@ def test_load_and_require_stay_private
   ensure
     ActiveSupport::Dependencies.hook!
   end
+
+  # Coverage for require_dependency can be found in the railties test suite.
 end

railties/test/application/zeitwerk_integration_test.rb

@@ -168,6 +168,14 @@ def user.to_path; "user"; end
     end
   end
 
+  test "require_dependency raises ArgumentError if the argument is not a String and does not respond to #to_path" do
+    assert_raises(ArgumentError) { require_dependency(Object.new) }
+  end
+
+  test "require_dependency raises LoadError if the given argument is not found" do
+    assert_raise(LoadError) { require_dependency("nonexistent_filename") }
+  end
+
   test "eager loading loads the application code" do
     $zeitwerk_integration_test_user = false
     $zeitwerk_integration_test_post = false