@username links insert <a href> tags twice

The same happens for #hashtags.
This is the only error that stops my site from completely validating as XHTML Transitional.

I have compared the source of the stable release and the dev release, and I have seen no differences in the code for the filter functions. So this problem also exists in dev.

It is caused by the regex in $matches[2] and $replacements[2] in twitter.module.

/**
 * This helper function converts Twitter-style @usernames and #hashtags into 
 * actual links.
 */
function twitter_link_filter($text, $prefix = '@', $destination = 'http://twitter.com/') {
  $matches = array(
    '/^' . $prefix . '([a-z0-9_]{0,15})/i',
    '/(\s+)' . $prefix . '([a-z0-9_]{0,15})/i',
    '/\>' . $prefix . '([a-z0-9_]{0,15})/i'
  );
  $replacements = array(
    '<a href="' . $destination . '${1}">' . $prefix . '${1}</a>',
    '${1}<a href="' . $destination . '${2}">' . $prefix . '${2}</a>',
    '><a href="' . $destination . '${1}">' . $prefix . '${1}</a>',
  );
  return preg_replace($matches, $replacements, $text); 
}

I'm not entirely sure what string it is trying to match but if you bump it to position 0 it fixes the issue.

  ...
  $matches = array(
    '/\>' . $prefix . '([a-z0-9_]{0,15})/i',
    '/^' . $prefix . '([a-z0-9_]{0,15})/i',
    '/(\s+)' . $prefix . '([a-z0-9_]{0,15})/i',
  );
  $replacements = array(
    '><a href="' . $destination . '${1}">' . $prefix . '${1}</a>',
    '<a href="' . $destination . '${1}">' . $prefix . '${1}</a>',
    '${1}<a href="' . $destination . '${2}">' . $prefix . '${2}</a>',
  );
  ...

Patched based on poseurtech's proposed fix attached.

#4 - Patch works for me! Thanks very much.

works here too.

Committed. Thanks!