Add YAML compatibility for objects from Rails 4.2

As of Ruby 2.2, Psych can handle any object which is marshallable. This
was not true on previous versions of Ruby, so our delegator types had to
provide their own implementation of `init_with` and `encode_with`.
Unfortunately, this doesn't match up with what Psych will do today.

Since by the time we hit this layer, the objects will have already been
created, I think it makes the most sense to just grab the current type
from the class.

1 files changed, 17 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/legacy_yaml_adapter.rb b/activerecord/lib/active_record/legacy_yaml_adapter.rb
index 0d018d4352..89dee58423 100644
--- a/activerecord/lib/active_record/legacy_yaml_adapter.rb
+++ b/activerecord/lib/active_record/legacy_yaml_adapter.rb
@@ -7,13 +7,29 @@ module ActiveRecord
       when 1 then coder
       else
         if coder["attributes"].is_a?(AttributeSet)
-          coder
+          Rails420.convert(klass, coder)
         else
           Rails41.convert(klass, coder)
         end
       end
     end
 
+    module Rails420
+      def self.convert(klass, coder)
+        attribute_set = coder["attributes"]
+
+        klass.attribute_names.each do |attr_name|
+          attribute = attribute_set[attr_name]
+          if attribute.type.is_a?(Delegator)
+            type_from_klass = klass.type_for_attribute(attr_name)
+            attribute_set[attr_name] = attribute.with_type(type_from_klass)
+          end
+        end
+
+        coder
+      end
+    end
+
     module Rails41
       def self.convert(klass, coder)
         attributes = klass.attributes_builder