Trac Template Debug

Here is a simplified template for debugging rendering issues or helping out when developing your own Trac / plugin templates. All it does is to find the main information available for rendering, and provide a simple (big) printout of the information at the end of each HTML page.

Drop it into your Trac project as templates/site.html, or alternatively if you already have a site.html then just copy & paste the main py:match section into your own file.

It is currently restricted to TRAC_ADMIN permission (<div py:if="'TRAC_ADMIN' in req.perm"...), but please use with caution for anything production related! There is no telling what information it may print, and there are no further checks. Be warned.

<html xmlns="http://www.w3.org/1999/xhtml" 

<!--! A new debug information <div> at the bottom of all pages -->
<py:match path="body" once="True">
<body py:attrs="select('@*')">
  <div py:if="'TRAC_ADMIN' in req.perm"
       style="width: 98%; margin: 5px; border: 2px solid green; padding: 10px; font-family: courier;"
       py:with="b_dir = globals()['__builtins__'].dir">
    <div style="text-indent: -30px; padding-left: 30px;">
      <!--! Some potentially very long lists... -->
      <p style="">perm for ${perm.username}: ${repr(perm.permissions())}</p>  
      <p>project: ${repr(project)}</p>  
      <p>trac: ${repr(trac or 'not defined')}</p>
      <p>context: ${repr(context)}</p>  
      <p>context members: ${repr(b_dir(context))}</p>
      <p><strong>context __dict__:</strong>
        <div py:for="item in sorted(context.__dict__.keys())">
            ${item}: ${repr(context.__dict__[item])}</div></p>
        <div py:for="item in sorted(req.environ.keys())">
            ${item}: ${repr(req.environ[item])}</div></p>
      <p><strong>req members:</strong> ${repr(b_dir(req))}</p>
      <p><strong>req __dict__:</strong>
        <div py:for="item in sorted(req.__dict__.keys())">
            ${to_unicode(item)}: ${to_unicode(repr(req.__dict__[item]))}</div></p>
      <p><strong>all objects from locals().['__data__']:</strong>
        <div py:for="item in sorted(locals()['__data__'].keys())">
            ${to_unicode(item)}: ${to_unicode(repr(locals()['__data__'][item]))}</div></p>
        <div py:for="key in sorted(globals()['__builtins__'].keys())">
            ${key}: ${repr(globals()['__builtins__'][key])}</div></p>
      <p py:with="sys = __import__('sys')">
        <strong>sys.path:</strong><br />


The debug template also allows you to play around with the information and try it out interactively. Here are some examples:

<p>Try using req.hef(): ${req.href('wiki')}</p>
<p>Test fetching an element: ${select('div[@id="mainnav"]')}</p>

If you want to avoid having to reload the Trac process for each template change, just turn on auto_reload to have it picked up automatically:

auto_reload = True


  • Posted: 2011-12-13 13:06 (Updated: 2012-07-10 00:18)
  • Categories: trac


1. simon@… -- 2012-07-10 00:50

I've updated the debug template slightly today by adding a few to_unicode() calls for output that may contain unknown and problematic output for rendering. It may be a pattern worth re-using decoding errors appear.