I recently had a need for a LazyObject which was callable. The __call__
meta method isn't forwarded to _wrapped, so it's an error to call, even if
the underlying _wrapped does support it.
In my case, was trying to do the following:
User = SimpleLazyObject(lambda: get_user_model())
User()...
I patched LazyObject to make it happy:
def _a_call_(self, *args, **kwargs):
if self._wrapped is empty:
self._setup()
return self._wrapped(*args, **kwargs)
LazyObject.__call__ = _a_call_.__get__(User)
Unfortunately, I then ran into a related problem -- by making LazyObject
callable, anyone passing a lazy user, e.g. request.user, to the ORM would
fall into the callable(value) branch:
https://github.com/django/django/blob/b77f26313cddbfde20dcf2661e9bd35458c2d1bd/django/db/models/sql/query.py#L1043
That then caused a new User to be constructed rather than using the
request.user.pk.
I see that callable criteria are deprecated there, but was wondering how
people would feel about adding a branch before that:
if ...
elif isinstance(value, LazyObject):
pass
elif callable(value):
...
That would allow request.user to still be used (as it no doubt widely is)
even after LazyObject grows a callable (if its underlying object has one).
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