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)

    def test_unsaved(self):

        poll = Poll(question="How?")

        msg = (

            "'Poll' instance needs to have a primary key value before this "

            "relationship can be used."

        )

        with self.assertRaisesMessage(ValueError, msg):

            poll.choice_set.all()

    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])