django/tests/null_queries/tests.py

from django.core.exceptions import FieldError
from django.test import TestCase

from .models import Choice, Inner, OuterA, OuterB, Poll


class NullQueriesTests(TestCase):

    def test_none_as_null(self):
        """
        Regression test for the use of None as a query value.

        None is interpreted as an SQL NULL, but only in __exact and __iexact
        queries.
        Set up some initial polls and choices
        """
        p1 = Poll(question='Why?')
        p1.save()
        c1 = Choice(poll=p1, choice='Because.')
        c1.save()
        c2 = Choice(poll=p1, choice='Why Not?')
        c2.save()

        # Exact query with value None returns nothing ("is NULL" in sql,
        # but every 'id' field has a value).
        self.assertSequenceEqual(Choice.objects.filter(choice__exact=None), [])

        # The same behavior for iexact query.
        self.assertSequenceEqual(Choice.objects.filter(choice__iexact=None), [])

        # Excluding the previous result returns everything.
        self.assertSequenceEqual(Choice.objects.exclude(choice=None).order_by('id'), [c1, c2])

        # Valid query, but fails because foo isn't a keyword
        msg = "Cannot resolve keyword 'foo' into field. Choices are: choice, id, poll, poll_id"
        with self.assertRaisesMessage(FieldError, msg):
            Choice.objects.filter(foo__exact=None)

        # Can't use None on anything other than __exact and __iexact
        with self.assertRaisesMessage(ValueError, 'Cannot use None as a query value'):
            Choice.objects.filter(id__gt=None)

        # Related managers use __exact=None implicitly if the object hasn't been saved.
        p2 = Poll(question="How?")
        self.assertEqual(repr(p2.choice_set.all()), '<QuerySet []>')

    def test_reverse_relations(self):
        """
        Querying across reverse relations and then another relation should
        insert outer joins correctly so as not to exclude results.
        """
        obj = OuterA.objects.create()
        self.assertSequenceEqual(OuterA.objects.filter(inner__third=None), [obj])
        self.assertSequenceEqual(OuterA.objects.filter(inner__third__data=None), [obj])

        inner = Inner.objects.create(first=obj)
        self.assertSequenceEqual(Inner.objects.filter(first__inner__third=None), [inner])

        # Ticket #13815: check if <reverse>_isnull=False does not produce
        # faulty empty lists
        outerb = OuterB.objects.create(data='reverse')
        self.assertSequenceEqual(OuterB.objects.filter(inner__isnull=False), [])
        Inner.objects.create(first=obj)
        self.assertSequenceEqual(OuterB.objects.exclude(inner__isnull=False), [outerb])