remove base class from belongs_to polymorphic association

activerecord/CHANGELOG.md

@@ -1,5 +1,28 @@
 ## Rails 6.0.0.alpha (Unreleased) ##
 
+*   Fix polymorphic true with inheritance.
+
+    Example: 
+
+        class Asset < ActiveRecord::Base
+          belongs_to :attachable, polymorphic: true
+        end
+
+        class Post < ActiveRecord::Base
+          # Post doesn't have a type column
+          has_many :assets, as: :attachable, dependent: :destroy
+        end
+
+        class GuestPost < Post
+        end
+
+        class MemberPost < Post
+        end
+
+    Now attachable_type can be Post, GuestPost or MemberPost
+
+    *Dilpreet Singh*
+
 *   Fix `#columns_for_distinct` of MySQL and PostgreSQL to make
     `ActiveRecord::FinderMethods#limited_ids_for` use correct primary key values
     even if `ORDER BY` columns include other table's primary key.

activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb

@@ -13,7 +13,7 @@ def klass
 
         def replace_keys(record)
           super
-          owner[reflection.foreign_type] = record ? record.class.base_class.name : nil
+          owner[reflection.foreign_type] = record ? record.class.name : nil
         end
 
         def different_target?(record)

activerecord/test/cases/associations/join_model_test.rb

@@ -118,13 +118,13 @@ def test_polymorphic_has_many_create_model_with_inheritance
     post = posts(:thinking)
     assert_instance_of SpecialPost, post
 
-    tagging = tags(:misc).taggings.create(taggable: post)
-    assert_equal "Post", tagging.taggable_type
+    tagging = tags(:misc).taggings.create(:taggable => post)
+    assert_equal "SpecialPost", tagging.taggable_type
   end
 
   def test_polymorphic_has_one_create_model_with_inheritance
-    tagging = tags(:misc).create_tagging(taggable: posts(:thinking))
-    assert_equal "Post", tagging.taggable_type
+    tagging = tags(:misc).create_tagging(:taggable => posts(:thinking))
+    assert_equal "SpecialPost", tagging.taggable_type
   end
 
   def test_set_polymorphic_has_many