F() expression not compatible with __range field look up

[liushaohua86@…]

class TestModel(models.Model):
    a = models.SmallIntegerField()
    b = models.SmallIntegerField()

TestModel.objects.filter(a__range=(F('b')-1, F('b')+1)

TypeError: int() argument must be a string or a number, not 'ExpressionNode'

[Baptiste Mispelon]

Hi,

I can reproduce this issue on latest master as well as on 1.6 so it doesn't appear to be related to the new custom lookup feature.

Regarding your formatting issues, you can make code blocks on trac using {{{ code goes here }}}, as explained on the WikiFormatting page.

Thanks.

[Tim Martin]

I've had a go at fixing this, the commit is here: ​https://github.com/django/django/compare/master...timmartin:bug22288

I'd like feedback on this fix, since I'm not sure I fully understand the potential wider impact of the changes I've made (though it passes all regression tests). It also looks like the changes in the pull request for #14030 will interact with this.

[Anssi Kääriäinen]

I checked the patch. It seems we need changes to too many places just to support something__range=(F('foo'), F('bar')). The main issue is that we have many rounds of value preparation.

The main issue here is that we just don't handle the case here value is an iterable correctly for value preparation. While the above mentioned commit touches the area around range lookups, we should likely fix all the lookups to lists of F() objects properly. Even if the only other example in core is somefield__in=[F()].

It might be better to wait for #14030 before applying this one.

In addition the tests of the above patch aren't correct, the code checks generated SQL, but that SQL differs between backends (quote character is not always ", and some backends IIRC use upper case table names).

Sorry for delay in commenting this issue.

[Richard Eames]

Any chance that this can be looked into now?

[Josh Smeaton]

I think a side effect of ​https://github.com/django/django/pull/5090/ is that range and in lookups will now understand expressions properly. I'm not certain of this though, it just looks like similar code paths.

​https://github.com/django/django/pull/5090/files#diff-b6b218ec29b7fb6a7d89868a94bfc73eR61

In fact, I'll incorporate the test case above into this patch to check.

[Josh Smeaton]

Nope, the linked patch doesn't alter the path at all.