Showing Text_Wiki errors on web page

I found pearwiki_filter being very silent if Text_Wiki is throwing errors. There will be no text output (Text_Wiki's fault) and no Text_Wiki error message.

The following patch changes at least pearwiki_filter to show Text_Wiki errors (if triggered by PEAR_Error::throwError()) by using a callback function for PEAR_Error.

Note: Getting Text_Wiki to show at least the output up to the point where Wiki syntax errors are detected can be done by changing Text/Wiki.php::render() at around line 1056: Instead of returning the PEAR_Error object do return the so far rendered output:

if ($tokenStack[count($tokenStack) - 1] != $rule) {
  Text_Wiki::error('Unbalanced tokens, check your syntax');
  return $this->output;
}

This issue is currently discussed here: http://pear.php.net/bugs/bug.php?id=14401

Attention: the attached patch includes my patch to Invalide node paths submitted here: http://drupal.org/node/227032