class Erubi::Engine

def add_text(text)

Must be called with a string, cannot be called with nil (Rails's subclass depends on it).
Add raw text to the template. Modifies argument if argument is mutable as a memory optimization. 
def add_text(text)
  return if text.empty?
  if text.frozen?
    text = text.gsub(/['\\]/, '\\\\\&')
  else
    text.gsub!(/['\\]/, '\\\\\&')
  end
  with_buffer{@src << " << '" << text << @text_end}
end