From 5f25aa7cbab2a9f9c076131c98089c39ea7deff3 Mon Sep 17 00:00:00 2001
From: "Mark J. Lehman" <markjlehman@gmail.com>
Date: Wed, 29 Jan 2020 13:10:35 -0800
Subject: [PATCH] Fix Rails 6.0 deprecation on `class.parent`

---
 lib/action_controller/serialization.rb | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/action_controller/serialization.rb b/lib/action_controller/serialization.rb
index d8aaef9a..1593dd14 100644
--- a/lib/action_controller/serialization.rb
+++ b/lib/action_controller/serialization.rb
@@ -60,7 +60,15 @@ module ActionController
     private
 
     def namespace_for_serializer
-      @namespace_for_serializer ||= self.class.parent unless self.class.parent == Object
+      @namespace_for_serializer ||= namespace_for_class(self.class) unless namespace_for_class(self.class) == Object
+    end
+
+    def namespace_for_class(klass)
+      if Module.method_defined?(:module_parent)
+        klass.module_parent
+      else
+        klass.parent
+      end
     end
 
     def default_serializer(resource)