Datamapper DataMapper

Having a model with lazy attributes (Text in my case) I got unexpected results when I call update_attributes with unchanged values. For example:

class Document
  include DataMapper::Resource

  property :id, Integer, :serial => true
  property :title, String
  property :description, Text
end

So in my controller when I update it I call the following

if @document.update_attributes(params[:document]) || !(@document.dirty?)
  redirect url(:document, @document)
else
  render :edit
end

The problem is when the new value is the same as the current of the lazy loaded attribute, because it marks it dirty, when it's actually not.

I've investigated a little bit, and the problem is when it is trying to set the new value it doesn't have the current value so the comparison is false.

# dm-core/lib/property.rb:414

    def set(resource, value)
      new_value = typecast(value)
      old_value = get!(resource)

      # skip setting the property if the new value is equal
      # to the old value, and the old value was defined
      return if new_value == old_value && resource.attribute_loaded?(name)

      resource.original_values[name] = old_value unless resource.original_values.has_key?(name)

      set!(resource, new_value)
    end

As we see here it tries to compare old_value (which is nil because it's not loaded) to the new_value. So it goes and mark it as dirty.

This wouldn't be a problem, we might just overwrite the value, but the mysql adapter is returning false. It says that no row was updated, which would be right since the values are the same.

I think the solution would be to force loading when updating a record, but I don't know if that would be the best path.