Fix that models can clobber each others' attachment reflections

Consider the following model definitions:

    class User < ApplicationRecord
      has_one_attached :avatar
    end

    class Group < ApplicationRecord
      has_one_attached :avatar
    end

If you attempt to reflect on the User model's avatar attachment via User.reflect_on_attachment, you could receive a reflection for the Group model's avatar attachment. Fix this by ensuring that each model class uses its own Hash object to track attachment reflections.

1 files changed, 2 insertions, 2 deletions

diff --git a/activestorage/lib/active_storage/reflection.rb b/activestorage/lib/active_storage/reflection.rb
index 04a1b20882..ce248c88b5 100644
--- a/activestorage/lib/active_storage/reflection.rb
+++ b/activestorage/lib/active_storage/reflection.rb
@@ -19,8 +19,8 @@ module ActiveStorage
     end
 
     module ReflectionExtension # :nodoc:
-      def add_attachment_reflection(ar, name, reflection)
-        ar.attachment_reflections.merge!(name.to_s => reflection)
+      def add_attachment_reflection(model, name, reflection)
+        model.attachment_reflections = model.attachment_reflections.merge(name.to_s => reflection)
       end
 
       private