spree_site.rb

module SpreeSite
  class Engine < Rails::Engine

    def self.activate
      Order.class_eval do
        def artworks; true; end
      end
    end

    config.to_prepare &method(:activate).to_proc
    
    ActionDispatch::Callbacks.after { SpreeSite::Engine.activate } #<<<<- I added this line

  end
end

=begin
reload! reloads all the engines, calls to_prepare and then removes 
constants ( in that order). Note that when you call console! then the 
constants are dropped at the very end. So after console! when you do

> Order.first

then vm does not find Order already loaded since it was removed at the 
end of console!. Now because of autoloading Order is loaded from app/models 
but this Order does not have the artworks method.

Solution:

ActionDispatch::Callbacks provide an "after" hook. I used it to reload 
Order class after Order class was removed. And this Order class is 
properly decorated with artworks method.
=end