Merge pull request #8072 from kennyj/remove_mattr_include_root_in_json

Allow include_root_in_json to be inheritable by using the class_attribute created by Active Model serialization module.

2 files changed, 16 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/serialization.rb b/activerecord/lib/active_record/serialization.rb
index 6a511c307b..6b55af4205 100644
--- a/activerecord/lib/active_record/serialization.rb
+++ b/activerecord/lib/active_record/serialization.rb
@@ -5,7 +5,6 @@ module ActiveRecord #:nodoc:
     include ActiveModel::Serializers::JSON
 
     included do
-      mattr_accessor :include_root_in_json, instance_accessor: false
       self.include_root_in_json = true
     end
 
diff --git a/activerecord/test/cases/serialization_test.rb b/activerecord/test/cases/serialization_test.rb
index 25b860878a..eb9cb91e32 100644
--- a/activerecord/test/cases/serialization_test.rb
+++ b/activerecord/test/cases/serialization_test.rb
@@ -45,4 +45,20 @@ class SerializationTest < ActiveRecord::TestCase
       assert_equal @contact_attributes[:awesome], contact.awesome, "For #{format}"
     end
   end
+
+  def test_include_root_in_json_allows_inheritance
+    original_root_in_json = ActiveRecord::Base.include_root_in_json
+    ActiveRecord::Base.include_root_in_json = true
+
+    klazz = Class.new(ActiveRecord::Base)
+    klazz.table_name = 'topics'
+    assert klazz.include_root_in_json
+
+    klazz.include_root_in_json = false
+    assert ActiveRecord::Base.include_root_in_json
+    assert !klazz.include_root_in_json
+    assert !klazz.new.include_root_in_json
+  ensure
+    ActiveRecord::Base.include_root_in_json = original_root_in_json
+  end
 end