Why do I get "wrong number of arguments (3 for 2)" using Redcloth?

I'm trying to use Redcloth in my Ruby app, and it's giving me a wrong number of arguments (3 for 2) error even though I only have two arguments.

Here's my code:

def self.cleanup(string)
  if string == "" || string == nil
    ""
  else

            string = self.iconvert(string, "ascii", "utf8")

    RedCloth.include(RedCloth::Formatters::HTML)
    redcloth = RedCloth.new(string)
    redcloth.html_esc(string)
    string = string.strip
    string = string.gsub(/''/,"\"")
    string = string.gsub(/\r/," ")
    string = string.gsub(/\n/," ")
    string = string.gsub(/\<br \/\>/," ")
    string = string.gsub(/\<br\/\>/," ")
    string = string.gsub(/&nbsp;/," ")
    redcloth.clean_html(string, {})
    string
  end
end

This is the source code: http://redcloth.rubyforge.org/classes/RedCloth/Formatters/HTML.html#M000052

def clean_html( text, allowed_tags = BASIC_TAGS )
  text.gsub!( /<!\[CDATA\[/, '' )
  text.gsub!( /<(\/*)([A-Za-z]\w*)([^>]*?)(\s?\/?)>/ ) do |m|
  raw = $~
  tag = raw[2].downcase
  if allowed_tags.has_key? tag
    pcs = [tag]
    allowed_tags[tag].each do |prop|
      ['"', "'", ''].each do |q|
        q2 = ( q != '' ? q : '\s' )
        if raw[3] =~ /#{prop}\s*=\s*#{q}([^#{q2}]+)#{q}/i
          attrv = $1
          next if (prop == 'src' or prop == 'href') and not attrv =~ %r{^(http|https|ftp):}
          pcs << "#{prop}=\"#{attrv.gsub('"', '\\"')}\""
          break
        end
      end

Here's my log:

I, [2013-07-16T12:22:53.095073 #12321]  INFO -- : wrong number of arguments (3 for 2)
I, [2013-07-16T12:22:53.095281 #12321]  INFO -- : /home/emai/.rvm/gems/ruby-1.9.3-p448@edmund/gems/RedCloth-4.2.9/lib/redcloth/formatters/base.rb:46:in `method_missing'

Solution

You're getting the error because the definition of method_missing in that Redcloth source file (base.rb) is defined with just two arguments (and no splat operator) and you are invoking an undefined method with two arguments which, when added to the method name, results in three arguments being passed to method_missing.

The offending call appears to be the call to redcloth.clean_html. As you noted in your comment, clean_html is a private method, so it's not accessible to you through the normal object.method invocation mechanism.