Returning immutable attributes protects against surprises

Author: bf4

lib/active_model_serializers/model.rb

@@ -42,10 +42,11 @@ def updated_at
       defined?(@updated_at) ? @updated_at : File.mtime(__FILE__)
     end
 
+    # @return [Hash] immutable representation of declared attributes
     def attributes
       attribute_names.each_with_object({}) do |attribute_name, result|
-        result[attribute_name] = public_send(attribute_name)
-      end.with_indifferent_access
+        result[attribute_name.freeze] = public_send(attribute_name).freeze
+      end.with_indifferent_access.freeze
     end
 
     # The following methods are needed to be minimally implemented for ActiveModel::Errors

test/cache_test.rb

@@ -532,7 +532,7 @@ def test_fragment_fetch_with_virtual_attributes
       role_hash = role_serializer.fetch_attributes_fragment(adapter_instance)
       assert_equal(role_hash, expected_result)
 
-      role.attributes[:id] = 'this has been updated'
+      role.id = 'this has been updated'
       role.name = 'this was cached'
 
       role_hash = role_serializer.fetch_attributes_fragment(adapter_instance)