#15791: New feature: callable objects can signal that templates should never
call
them
-------------------------------------+-------------------------------------
Reporter: ejucovy | Owner: nobody
Type: New | Status: new
feature | Component: Template system
Milestone: | Severity: Normal
Version: SVN | Keywords:
Resolution: | Has patch: 1
Triage Stage: Ready for | Needs tests: 0
checkin |
Needs documentation: 0 |
Patch needs improvement: 0 |
-------------------------------------+-------------------------------------
Changes (by lukeplant):
* stage: Unreviewed => Ready for checkin
Comment:
It's unfortunate that we need this, as it seems a bit hacky.
However, it is a genuine problem. An alternative solution is to convert
callable objects to non-callable by some magic, so that the template
system does not need to be altered. But that seems just as bad, and will
probably have more gotchas.
Your solution follows the precedent of `alters_data`, while being
orthogonal to it (which I didn't realise at first), in that it allows
attributes of the callable to be accessed, while `alters_data` does not.
The 'nocall' filter or template tag would be much more work, and harder to
implement, and I don't think are practical. For large batches of callable
objects retrieved by some third-party library, I think a good enough
workaround is to wrap the data in a simple generator that adds the
'do_not_call_in_templates' attribute to instances where needed:
{{{
#!python
def mark_not_callable(objects):
for obj in objects:
obj.do_not_call_in_templates = True
# or possibly:
obj.some_sub_object.do_not_call_in_templates = True
yield obj
def view(request):
# ...
context['objects'] = mark_not_callable(some_objects)
}}}
`'do_not_call_in_templates'` seems a bit verbose, but it's explicit and
it's your bike-shed, so we'll leave that.
Thank you for the tests for alters_data. There are tests for other
callables in class 'Templates' in regressiontests/templates/tests.py, but
not for alters_data that I can find, and the nature of the tests means it
is good to explicitly test that the methods are not called, as you have
done. The simple `test_callable` test you have added can be left, because
it uses a class with a `__call__` method, while the existing test uses a
lambda, and its conceivable that having both types of callable tested
could be useful.
For future reference, I found one tiny nit, which I'll fix when I commit -
our coding style for templates is to do `{{ variable }}` and not
`{{variable}}`.
So, for all these reasons, marking accepted, and in fact, ready for
checkin. Thank you very much!
--
Ticket URL: <http://code.djangoproject.com/ticket/15791#comment:3>
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