module Haml::AttributeBuilder

def build_boolean!(escape_attrs, quote, format, buf, key, value)
  case value
  when true
    case format
    when :xhtml
      buf << " #{key}=#{quote}#{key}#{quote}"
    else
      buf << " #{key}"
    end
  when false, nil
    # omitted
  else
    buf << " #{key}=#{quote}#{escape_html(escape_attrs, value)}#{quote}"
  end
end