django template change behaviour to silent_variable_failure = False

Question

http://www.djangobook.com/en/beta/chapter10/

"Note that django.core.exceptions.ObjectDoesNotExist, which is the base class for all Django database API DoesNotExist exceptions, has silent_variable_failure = True. So if you’re using Django templates with Django model objects, any DoesNotExist exception will fail silently."

Whilst I'm developing I'd like to reverse this behaviour, i.e. silent_variable_failure = False. How do I make this change permanent whilst developing under django ?

Thanks, Nick

Answer 1

The Django template system looks for silent_variable_failure as an attribute of any exception.

This means you have do define your own exception with that attribute set to False.

For the standard ObjectDoesNotExist exception generated by the ORM, etc., the simplest solution would be to modify the Django sourcecode on your development box (django/core/exceptions.py).

If this was something you needed to change on a production system then you would need to 1) define your own exception class, 2) put a manager on your model that is called from the template (instead of using ORM methods directly), and then 3) catch DoesNotExist in your manager and re-raise the exception with your own class.

Answer 2

In settings.py I added TEMPLATE_STRING_IF_INVALID = "invalid string '%s'" See http://docs.djangoproject.com/en/dev/ref/templates/api/#invalid-template-variables for more info.

It includes this warning "Many templates, including those in the Admin site, rely upon the silence of the template system when a non-existent variable is encountered. If you assign a value other than '' to TEMPLATE_STRING_IF_INVALID, you will experience rendering problems with these templates and sites."