Suppressing exceptions in templates harmful for debugging

[joerg@…]

Even when TEMPLATE_DEBUG is enabled, Django will currently silently suppress all exceptions during template rendering.
This makes it hard to find typos in the template (misspelled variable names), but can also hide other errors.

The concrete problem I hit was the conversion to permalink and the resolver not knowing functions specified directly as object and not string.
As the exception was ignored, all users of the permalink used the empty string.

It would be nice if the exceptions can be easily logged either to stderr (manage.py runserver) or some file, potentially using another debug option in settings.py.

[Luke Plant]

See this discussion:

​http://groups.google.com/group/django-developers/browse_thread/thread/f323338045ac2e5e/

General conclusion: we need to examine individual tags and see whether they should fail silently or not. I agree that it is never useful for the URL tag to fail silently. I'll bring it up on the list

[Luke Plant]

(In [8211]) Fixed #8031 - url tag no longer silences NoReverseMatch exceptions since this is very rarely useful

[Luke Plant]

If there are any other tags where exceptions are being unhelpfully silenced, please open a new ticket. Silent variable failure is a deliberate feature e.g.

{{ foo.bar.baz }}

should return nothing if foo is None, or if foo.bar is None, or if foo.bar.baz is None.