[IPOL discuss] Added traceback for Mako exceptions

[Pascal Getreuer]

Wow, thanks Miguel! I sure have been stumped on Mako errors before, this
will really help.

Pascal



On Wed, Jun 11, 2014 at 5:51 AM, Miguel Colom <colom at cmla.ens-cachan.fr>
wrote:

> Dear all,
> since now, when it raised an exception during a Mako template rendering,
> CherryPy showed a traceback which in fact is not really informative. Most
> of the time, it shows just the name of the exception (nameError), but not
> which variable caused the problem or which file.
>
> I've modified base_app.py in order to use the RichTraceback() object from
> Mako. Now, when a unhandled template exception occurs, a different error
> page is shown, telling which file, line and contents of the line caused the
> failure.
>
> For example:
> File /home/miguel/ipolLocal/demo/app/81/template/archive_index.html, line
> 5, in render_body
> ${nbpublic} public archives out of ${nbtotal} online experiments with
>
> In the example we can see that it was line #5 of file archive_index.html
> which caused the problem, involving the ${nbpublic} and ${nbtotal}
> variables.
>
> You can checkout the new code from git (best option), or change your
> tmpl_out(.) function by this one:
>     def tmpl_out(self, tmpl_fname, **kwargs):
>         """
>         templating shortcut, populated with the default app attributes
>         """
>         # pass the app object
>         kwargs['app'] = self
>         # production flag
>         kwargs['prod'] = (cherrypy.config['server.environment']
>                           == 'production')
>
>         tmpl = self.tmpl_lookup.get_template(tmpl_fname)
>
>         # Render the template
>         # If an exception occurs, render an error page showing the
> traceback
>         try:
>             return tmpl.render(**kwargs)
>         except:
>             traceback_string = "<h1>IPOL template rendering error</h1>"
>             traceback_string += "<h2>Template: %s</h2>" % tmpl_fname
>             traceback_string += "<h2>kwargs: %s</h2>" % kwargs
>             traceback = RichTraceback()
>             for (filename, lineno, function, line) in traceback.traceback:
>                 traceback_string += \
>                     "File <b>%s</b>, line <b>%d</b>, in <b>%s</b><br>" % \
>                     (filename, lineno, function)
>                 traceback_string += line + "<br><br>"
>             traceback_string += "%s: %s" % \
>                 (str(traceback.error.__class__.__name__), \
>                 traceback.error) + "<br>"
>             return traceback_string
>
> (also add "from mako.exceptions import RichTraceback" before "from .
> import http").
>
> Best,
> Miguel
>
>
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-- 
Pascal Getreuer
CMLA, ENS Cachan
getreuer at cmla.ens-cachan.fr
www.getreuer.info
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