How do you debug Mako templates?

Question

So far I've found it impossible to produce usable tracebacks when Mako templates aren't coded correctly.

Is there any way to debug templates besides iterating for every line of code?

Answer 1

Mako actually provides a VERY nice way to track down errors in a template:

from mako import exceptions

try:
    template = lookup.get_template(uri)
    print template.render()
except:
    print exceptions.html_error_template().render()

Answer 2

Looking at the Flask-Mako source, I found an undocumented configuration parameter called MAKO_TRANSLATE_EXCEPTIONS.

Set this to False in your Flask app config and you'll get nice exceptions bubbling up from the template. This accomplishes the same thing as @Mariano suggested, without needing to edit the source. Apparently, this parameter was added after Mariano's answer.

Answer 3

I break them down into pieces, and then reassemble the pieces when I've found the problem.

Not good, but it's really hard to tell what went wrong in a big, complex template.