1 files changed, 86 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/module/introspection.rb b/activesupport/lib/active_support/core_ext/module/introspection.rb
new file mode 100644
index 0000000000..9b6df40596
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/module/introspection.rb
@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+require "active_support/inflector"
+
+class Module
+  # Returns the name of the module containing this one.
+  #
+  #   M::N.module_parent_name # => "M"
+  def module_parent_name
+    if defined?(@parent_name)
+      @parent_name
+    else
+      parent_name = name =~ /::[^:]+\Z/ ? $`.freeze : nil
+      @parent_name = parent_name unless frozen?
+      parent_name
+    end
+  end
+
+  def parent_name
+    ActiveSupport::Deprecation.warn(<<-MSG.squish)
+      `Module#parent_name` has been renamed to `module_parent_name`.
+      `parent_name` is deprecated and will be removed in Rails 6.1.
+    MSG
+    module_parent_name
+  end
+
+  # Returns the module which contains this one according to its name.
+  #
+  #   module M
+  #     module N
+  #     end
+  #   end
+  #   X = M::N
+  #
+  #   M::N.module_parent # => M
+  #   X.module_parent    # => M
+  #
+  # The parent of top-level and anonymous modules is Object.
+  #
+  #   M.module_parent          # => Object
+  #   Module.new.module_parent # => Object
+  def module_parent
+    module_parent_name ? ActiveSupport::Inflector.constantize(module_parent_name) : Object
+  end
+
+  def parent
+    ActiveSupport::Deprecation.warn(<<-MSG.squish)
+      `Module#parent` has been renamed to `module_parent`.
+      `parent` is deprecated and will be removed in Rails 6.1.
+    MSG
+    module_parent
+  end
+
+  # Returns all the parents of this module according to its name, ordered from
+  # nested outwards. The receiver is not contained within the result.
+  #
+  #   module M
+  #     module N
+  #     end
+  #   end
+  #   X = M::N
+  #
+  #   M.module_parents    # => [Object]
+  #   M::N.module_parents # => [M, Object]
+  #   X.module_parents    # => [M, Object]
+  def module_parents
+    parents = []
+    if module_parent_name
+      parts = module_parent_name.split("::")
+      until parts.empty?
+        parents << ActiveSupport::Inflector.constantize(parts * "::")
+        parts.pop
+      end
+    end
+    parents << Object unless parents.include? Object
+    parents
+  end
+
+  def parents
+    ActiveSupport::Deprecation.warn(<<-MSG.squish)
+      `Module#parents` has been renamed to `module_parents`.
+      `parents` is deprecated and will be removed in Rails 6.1.
+    MSG
+    module_parents
+  end
+end