serialization cannot be allowed to return new objects for the same inputs in the same object

a.rb

class C
  include Mongoid::Document

  class Struct < ::Hash
    def method_missing(method, *args, &block)
      key = method.to_s
      has_key?(key) ? fetch(key) : super
    end

    class Type
      old_skool = defined?(Mongoid::Fields::Serializable)

      if old_skool
        include Mongoid::Fields::Serializable
        
        def deserialize(hash)
          Struct.new(hash)
        end
        
        def serialize(hash)
          hash
        end
      else
      
        def self.demongoize(hash)
          Struct.new(hash)
        end
        
        def mongoize(hash)
          hash
        end
      end
    end
  end
  
  field(:data, :type => Struct::Type, :default => proc{ Struct.new })
end


c = C.new

data = c.data

data.update(:key => :val)


p data             #=> {:key=>:val}
p c.data           #=> {}

p data.object_id   #=> 70178108577780
p c.data.object_id #=> 70178108577340

p c.data.object_id #=> 70178108577220