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from django.test import TestCase
from .models import Article, Car, Driver, Reporter
class ManyToOneNullTests(TestCase):
@classmethod
def setUpTestData(cls):
# Create a Reporter.
cls.r = Reporter(name="John Smith")
cls.r.save()
# Create an Article.
cls.a = Article(headline="First", reporter=cls.r)
cls.a.save()
# Create an Article via the Reporter object.
cls.a2 = cls.r.article_set.create(headline="Second")
# Create an Article with no Reporter by passing "reporter=None".
cls.a3 = Article(headline="Third", reporter=None)
cls.a3.save()
# Create another article and reporter
cls.r2 = Reporter(name="Paul Jones")
cls.r2.save()
cls.a4 = cls.r2.article_set.create(headline="Fourth")
def test_get_related(self):
self.assertEqual(self.a.reporter.id, self.r.id)
# Article objects have access to their related Reporter objects.
r = self.a.reporter
self.assertEqual(r.id, self.r.id)
def test_created_via_related_set(self):
self.assertEqual(self.a2.reporter.id, self.r.id)
def test_related_set(self):
# Reporter objects have access to their related Article objects.
self.assertSequenceEqual(self.r.article_set.all(), [self.a, self.a2])
self.assertSequenceEqual(
self.r.article_set.filter(headline__startswith="Fir"), [self.a]
)
self.assertEqual(self.r.article_set.count(), 2)
def test_created_without_related(self):
self.assertIsNone(self.a3.reporter)
# Need to reget a3 to refresh the cache
a3 = Article.objects.get(pk=self.a3.pk)
with self.assertRaises(AttributeError):
getattr(a3.reporter, "id")
# Accessing an article's 'reporter' attribute returns None
# if the reporter is set to None.
self.assertIsNone(a3.reporter)
# To retrieve the articles with no reporters set, use
# "reporter__isnull=True".
self.assertSequenceEqual(
Article.objects.filter(reporter__isnull=True), [self.a3]
)
# We can achieve the same thing by filtering for the case where the
# reporter is None.
self.assertSequenceEqual(Article.objects.filter(reporter=None), [self.a3])
# Set the reporter for the Third article
self.assertSequenceEqual(self.r.article_set.all(), [self.a, self.a2])
self.r.article_set.add(a3)
self.assertSequenceEqual(
self.r.article_set.all(),
[self.a, self.a2, self.a3],
)
# Remove an article from the set, and check that it was removed.
self.r.article_set.remove(a3)
self.assertSequenceEqual(self.r.article_set.all(), [self.a, self.a2])
self.assertSequenceEqual(
Article.objects.filter(reporter__isnull=True), [self.a3]
)
def test_remove_from_wrong_set(self):
self.assertSequenceEqual(self.r2.article_set.all(), [self.a4])
# Try to remove a4 from a set it does not belong to
with self.assertRaises(Reporter.DoesNotExist):
self.r.article_set.remove(self.a4)
self.assertSequenceEqual(self.r2.article_set.all(), [self.a4])
def test_set(self):
# Use manager.set() to allocate ForeignKey. Null is legal, so existing
# members of the set that are not in the assignment set are set to
# null.
self.r2.article_set.set([self.a2, self.a3])
self.assertSequenceEqual(self.r2.article_set.all(), [self.a2, self.a3])
# Use manager.set(clear=True)
self.r2.article_set.set([self.a3, self.a4], clear=True)
self.assertSequenceEqual(self.r2.article_set.all(), [self.a4, self.a3])
# Clear the rest of the set
self.r2.article_set.set([])
self.assertSequenceEqual(self.r2.article_set.all(), [])
self.assertSequenceEqual(
Article.objects.filter(reporter__isnull=True),
[self.a4, self.a2, self.a3],
)
def test_set_clear_non_bulk(self):
# 2 queries for clear(), 1 for add(), and 1 to select objects.
with self.assertNumQueries(4):
self.r.article_set.set([self.a], bulk=False, clear=True)
def test_assign_clear_related_set(self):
# Use descriptor assignment to allocate ForeignKey. Null is legal, so
# existing members of the set that are not in the assignment set are
# set to null.
self.r2.article_set.set([self.a2, self.a3])
self.assertSequenceEqual(self.r2.article_set.all(), [self.a2, self.a3])
# Clear the rest of the set
self.r.article_set.clear()
self.assertSequenceEqual(self.r.article_set.all(), [])
self.assertSequenceEqual(
Article.objects.filter(reporter__isnull=True),
[self.a, self.a4],
)
def test_assign_with_queryset(self):
# Querysets used in reverse FK assignments are pre-evaluated
# so their value isn't affected by the clearing operation in
# RelatedManager.set() (#19816).
self.r2.article_set.set([self.a2, self.a3])
qs = self.r2.article_set.filter(headline="Second")
self.r2.article_set.set(qs)
self.assertEqual(1, self.r2.article_set.count())
self.assertEqual(1, qs.count())
def test_add_efficiency(self):
r = Reporter.objects.create()
articles = []
for _ in range(3):
articles.append(Article.objects.create())
with self.assertNumQueries(1):
r.article_set.add(*articles)
self.assertEqual(r.article_set.count(), 3)
def test_clear_efficiency(self):
r = Reporter.objects.create()
for _ in range(3):
r.article_set.create()
with self.assertNumQueries(1):
r.article_set.clear()
self.assertEqual(r.article_set.count(), 0)
def test_related_null_to_field(self):
c1 = Car.objects.create()
d1 = Driver.objects.create()
self.assertIs(d1.car, None)
with self.assertNumQueries(0):
self.assertEqual(list(c1.drivers.all()), [])
def test_unsaved(self):
msg = (
"'Car' instance needs to have a primary key value before this relationship "
"can be used."
)
with self.assertRaisesMessage(ValueError, msg):
Car(make="Ford").drivers.all()
def test_related_null_to_field_related_managers(self):
car = Car.objects.create(make=None)
driver = Driver.objects.create()
msg = (
f'"{car!r}" needs to have a value for field "make" before this '
f"relationship can be used."
)
with self.assertRaisesMessage(ValueError, msg):
car.drivers.add(driver)
with self.assertRaisesMessage(ValueError, msg):
car.drivers.create()
with self.assertRaisesMessage(ValueError, msg):
car.drivers.get_or_create()
with self.assertRaisesMessage(ValueError, msg):
car.drivers.update_or_create()
with self.assertRaisesMessage(ValueError, msg):
car.drivers.remove(driver)
with self.assertRaisesMessage(ValueError, msg):
car.drivers.clear()
with self.assertRaisesMessage(ValueError, msg):
car.drivers.set([driver])
with self.assertNumQueries(0):
self.assertEqual(car.drivers.count(), 0)
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