Allow parent being the owner of an alias attribute method

When an abstract class inherited from an Active Record model
defines an alias attribute Rails should expect the original methods
of the aliased attribute to be defined in the parent class and avoid
raising deprecation warning.

Author: nvasilevski

activerecord/lib/active_record/attribute_methods.rb

@@ -87,7 +87,8 @@ def alias_attribute_method_definition(code_generator, pattern, new_name, old_nam
         old_name = old_name.to_s
 
         method_defined = method_defined?(target_name) || private_method_defined?(target_name)
-        manually_defined = method_defined && self.instance_method(target_name).owner != generated_attribute_methods
+        manually_defined = method_defined &&
+          !self.instance_method(target_name).owner.is_a?(GeneratedAttributeMethods)
         reserved_method_name = ::ActiveRecord::AttributeMethods.dangerous_attribute_methods.include?(target_name)
 
         if manually_defined && !reserved_method_name

activerecord/test/cases/attribute_methods_test.rb

@@ -1266,6 +1266,28 @@ class ChildWithDeprecatedBehaviorResolved < ClassWithDeprecatedAliasAttributeBeh
     assert_equal("overridden_subject_was", obj.subject_was)
   end
 
+  ParentWithAlias = Class.new(ActiveRecord::Base) do
+    self.table_name = "topics"
+    alias_attribute :parents_subject, :title
+  end
+
+  AbstractClassInBetween = Class.new(ParentWithAlias) do
+    self.abstract_class = true
+    alias_attribute :parents_subject, :title
+  end
+
+  ChildWithAnAliasFromAbstractClass = Class.new(AbstractClassInBetween) do
+  end
+
+  test "#alias_attribute with the same alias as parent doesn't issue a deprecation" do
+    ParentWithAlias.new # eagerly generate parents alias methods
+    obj = assert_not_deprecated(ActiveRecord.deprecator) do
+      ChildWithAnAliasFromAbstractClass.new
+    end
+    obj.title = "hey"
+    assert_equal("hey", obj.parents_subject)
+  end
+
   test "#alias_attribute method on an abstract class is available on subclasses" do
     superclass = Class.new(ActiveRecord::Base) do
       self.abstract_class = true