it s possible to create a working related field that doesn t use any joining columns as long as an extra restriction is supplied it s possible to create a working related field that doesn t use any joining columns as long as an extra restriction is supplied
from django.test import TestCase

from .models import SlugPage


class RestrictedConditionsTests(TestCase):
    @classmethod
    def setUpTestData(cls):
        slugs = [
            "a",
            "a/a",
            "a/b",
            "a/b/a",
            "x",
            "x/y/z",
        ]
        SlugPage.objects.bulk_create([SlugPage(slug=slug) for slug in slugs])

    def test_restrictions_with_no_joining_columns(self):
        
        a = SlugPage.objects.get(slug="a")
        self.assertEqual(
            [p.slug for p in SlugPage.objects.filter(ascendants=a)],
            ["a", "a/a", "a/b", "a/b/a"],
        )
        self.assertEqual(
            [p.slug for p in a.descendants.all()],
            ["a", "a/a", "a/b", "a/b/a"],
        )

        aba = SlugPage.objects.get(slug="a/b/a")
        self.assertEqual(
            [p.slug for p in SlugPage.objects.filter(descendants__in=[aba])],
            ["a", "a/b", "a/b/a"],
        )
        self.assertEqual(
            [p.slug for p in aba.ascendants.all()],
            ["a", "a/b", "a/b/a"],
        )

    def test_empty_join_conditions(self):
        x = SlugPage.objects.get(slug="x")
        message = "Join generated an empty ON clause."
        with self.assertRaisesMessage(ValueError, message):
            list(SlugPage.objects.filter(containers=x))