Provide a better error message for unsupported classes in `serialize`

We only support classes which provide a no-args constructor to use as a
default value. We can provide a more helpful error message if we catch
this when `serialize` is called, rather than letting it error when you
try to assign the attribute.

Fixes #18224

1 files changed, 11 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/coders/yaml_column.rb b/activerecord/lib/active_record/coders/yaml_column.rb
index d3d7396c91..9ea22ed798 100644
--- a/activerecord/lib/active_record/coders/yaml_column.rb
+++ b/activerecord/lib/active_record/coders/yaml_column.rb
@@ -8,6 +8,7 @@ module ActiveRecord
 
       def initialize(object_class = Object)
         @object_class = object_class
+        check_arity_of_constructor
       end
 
       def dump(obj)
@@ -33,6 +34,16 @@ module ActiveRecord
 
         obj
       end
+
+      private
+
+      def check_arity_of_constructor
+        begin
+          load(nil)
+        rescue ArgumentError
+          raise ArgumentError, "Cannot serialize #{object_class}. Classes passed to `serialize` must have a 0 argument constructor."
+        end
+      end
     end
   end
 end