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))