Now explicit serializated objects retuns new objects when nil

This would mean that you can't save nil values for serialized attributes with a specific class anymore. Maybe an extra option :allow_nil or something would be a good solution?

No. These patch don't change the default behavior.

When you do something like these

  serialize :properties

The behaviour is the same. You can set nil to properties.

But if you say that properties is a hash, the empty value for a hash is an empty Hash.

class Topic < AR::Base
  serialize :properties, Hash
end

t = Topic.new
t.properties['name'] = 'Guillermo'
t.save

t.properties.clear
t.save

Obviously you don't have to think or initialize an uninizialize hash, openstruc, array, etc...

These reason of these ticket is that i have always do something like these

class User < AR::Base
  serialize :preferences, OpenStruct
  def preferences
    read_attribute :preferences || OpenStruct.new
  end

I think about add something like allow_nil but i don't found any case where a prefere to save a nil value instead of a empty Hash, Array, OpenStruct.