mongoid_only_patch.rb

# encoding: utf-8

# https://github.com/mongodb/mongoid/blob/4789bfffd3cbfa065eb7be7f34fbac122278a0ae/lib/mongoid/criteria.rb#L324

require "mongoid/criteria"

module Mongoid
  class Criteria
    OnlyWhenDefaultScopeError = Class.new(StandardError)

    alias :mongoid_criteria_only :only
    private :mongoid_criteria_only

    def only(*args)
      if scoped? && options[:fields].present? && args.flatten != options[:fields].keys
        raise OnlyWhenDefaultScopeError, "Using #{klass}#only for criteria with default_scope already defining field for projection.\nUse #{klass}#unsoped method."
      end

      mongoid_criteria_only(*args)
    end
  end
end