class Haml::Buffer

def self.merge_attrs(to, from)
  if to['id'] && from['id']
    to['id'] << '_' << from.delete('id')
  elsif to['id'] || from['id']
    from['id'] ||= to['id']
  end
  if to['class'] && from['class']
    # Make sure we don't duplicate class names
    from['class'] = (from['class'].split(' ') | to['class'].split(' ')).join(' ')
  elsif to['class'] || from['class']
    from['class'] ||= to['class']
  end
  to.merge!(from)
end