Don't query the database schema when calling `serialize`

We need to decorate the types lazily. This is extracted to a separate
API, as there are other refactorings that will be able to make use of
it, and to allow unit testing the finer points more granularly.

1 files changed, 2 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/serialization.rb b/activerecord/lib/active_record/attribute_methods/serialization.rb
index 148fc9eae5..60debb7d18 100644
--- a/activerecord/lib/active_record/attribute_methods/serialization.rb
+++ b/activerecord/lib/active_record/attribute_methods/serialization.rb
@@ -58,11 +58,9 @@ module ActiveRecord
                     Coders::YAMLColumn.new(class_name_or_coder)
                   end
 
-          type = columns_hash[attr_name.to_s].cast_type
-          if type.serialized?
-            type = type.subtype
+          decorate_attribute_type(attr_name, :serialize) do |type|
+            Type::Serialized.new(type, coder)
           end
-          property attr_name, Type::Serialized.new(type, coder)
 
           # merge new serialized attribute and create new hash to ensure that each class in inheritance hierarchy
           # has its own hash of own serialized attributes