django/tests/null_fk/tests.py

from django.db.models import Q
from django.test import TestCase

from .models import Comment, Forum, Item, Post, PropertyValue, SystemDetails, SystemInfo


class NullFkTests(TestCase):
    def test_null_fk(self):
        d = SystemDetails.objects.create(details="First details")
        s = SystemInfo.objects.create(system_name="First forum", system_details=d)
        f = Forum.objects.create(system_info=s, forum_name="First forum")
        p = Post.objects.create(forum=f, title="First Post")
        c1 = Comment.objects.create(post=p, comment_text="My first comment")
        c2 = Comment.objects.create(comment_text="My second comment")

        # Starting from comment, make sure that a .select_related(...) with a specified
        # set of fields will properly LEFT JOIN multiple levels of NULLs (and the things
        # that come after the NULLs, or else data that should exist won't). Regression
        # test for #7369.
        c = Comment.objects.select_related().get(id=c1.id)
        self.assertEqual(c.post, p)
        self.assertIsNone(Comment.objects.select_related().get(id=c2.id).post)

        self.assertQuerySetEqual(
            Comment.objects.select_related("post__forum__system_info").all(),
            [
                (c1.id, "My first comment", "<Post: First Post>"),
                (c2.id, "My second comment", "None"),
            ],
            transform=lambda c: (c.id, c.comment_text, repr(c.post)),
        )

        # Regression test for #7530, #7716.
        self.assertIsNone(
            Comment.objects.select_related("post").filter(post__isnull=True)[0].post
        )

        self.assertQuerySetEqual(
            Comment.objects.select_related("post__forum__system_info__system_details"),
            [
                (c1.id, "My first comment", "<Post: First Post>"),
                (c2.id, "My second comment", "None"),
            ],
            transform=lambda c: (c.id, c.comment_text, repr(c.post)),
        )

    def test_combine_isnull(self):
        item = Item.objects.create(title="Some Item")
        pv = PropertyValue.objects.create(label="Some Value")
        item.props.create(key="a", value=pv)
        item.props.create(key="b")  # value=NULL
        q1 = Q(props__key="a", props__value=pv)
        q2 = Q(props__key="b", props__value__isnull=True)

        # Each of these individually should return the item.
        self.assertEqual(Item.objects.get(q1), item)
        self.assertEqual(Item.objects.get(q2), item)

        # Logically, qs1 and qs2, and qs3 and qs4 should be the same.
        qs1 = Item.objects.filter(q1) & Item.objects.filter(q2)
        qs2 = Item.objects.filter(q2) & Item.objects.filter(q1)
        qs3 = Item.objects.filter(q1) | Item.objects.filter(q2)
        qs4 = Item.objects.filter(q2) | Item.objects.filter(q1)

        # Regression test for #15823.
        self.assertEqual(list(qs1), list(qs2))
        self.assertEqual(list(qs3), list(qs4))