[patch] Filters no longer parsed for unresolved variables

[Chris Beaven]

Changeset [3268] made the following change for the resolve method in django/template/init.py:

-            obj = settings.TEMPLATE_STRING_IF_INVALID
+            if ignore_failures:
+                return None
+            else:
+                return settings.TEMPLATE_STRING_IF_INVALID

Because TEMPLATE_STRING_IF_INVALID is returned now rather than being set in obj (which is then passed to any filters), the filters are not parsed on an unresolved variable.
This changes the behaviour of the default and default_if_none filters.

I believe the last line of that patch should have been:

+                obj = settings.TEMPLATE_STRING_IF_INVALID

Perhaps the return None line should change as well, but it's just used in testing at the moment.

[Chris Beaven]

Here's the related ​thread on Google groups

[Russell Keith-Magee]

(In [3714]) Fixes #2637 -- Clarified handling of TEMPLATE_STRING_IF_INVALID, especially with regards to filtering of invalid values. Modified unit tests to test both empty and non-empty values for TEMPLATE_STRING_IF_INVALID. Thanks to SmileyChris for identifying and helping to resolve this bug.