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 ever

Answer 1

My main frustration with Mako was that it was hard to see what was happening in the template. As the template code is a runnable object that is in-memory, no debugger can look into it.

One solution is to write the template code to file, and re-run the template using this file as a standard python module. Then you can debug to your hearts content.

An example:

import sys
from mako import exceptions, template 
from mako.template import DefTemplate
from mako.runtime import _render



try:
    template.render(**arguments))
except:
    # Try to re-create the error using a proper file template
    # This will give a clearer error message.
    with open('failed_template.py', 'w') as out:
        out.write(template._code)
    import failed_template
    data = dict(callable=failed_template.render_body, **arguments)
    try:
        _render(DefTemplate(template, failed_template.render_body),
                failed_template.render_body,
                [],
                data)
    except:
        msg = '\n'%arguments
        msg += exceptions.text_error_template().render()
        print(msg, file=sys.stderr)
        raise