django/tests/model_fields/test_foreignkey.py

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from decimal import Decimal
from django.apps import apps
from django.core import checks
from django.db import models
from django.test import TestCase, skipIfDBFeature
from django.test.utils import isolate_apps
from .models import Bar, FkToChar, Foo, PrimaryKeyCharModel
class ForeignKeyTests(TestCase):
def test_callable_default(self):
"""A lazy callable may be used for ForeignKey.default."""
a = Foo.objects.create(id=1, a='abc', d=Decimal('12.34'))
b = Bar.objects.create(b='bcd')
self.assertEqual(b.a, a)
@skipIfDBFeature('interprets_empty_strings_as_nulls')
def test_empty_string_fk(self):
"""
Empty strings foreign key values don't get converted to None (#19299).
"""
char_model_empty = PrimaryKeyCharModel.objects.create(string='')
fk_model_empty = FkToChar.objects.create(out=char_model_empty)
fk_model_empty = FkToChar.objects.select_related('out').get(id=fk_model_empty.pk)
self.assertEqual(fk_model_empty.out, char_model_empty)
@isolate_apps('model_fields')
def test_warning_when_unique_true_on_fk(self):
class Foo(models.Model):
pass
class FKUniqueTrue(models.Model):
fk_field = models.ForeignKey(Foo, models.CASCADE, unique=True)
model = FKUniqueTrue()
expected_warnings = [
checks.Warning(
'Setting unique=True on a ForeignKey has the same effect as using a OneToOneField.',
hint='ForeignKey(unique=True) is usually better served by a OneToOneField.',
obj=FKUniqueTrue.fk_field.field,
id='fields.W342',
)
]
warnings = model.check()
self.assertEqual(warnings, expected_warnings)
def test_related_name_converted_to_text(self):
rel_name = Bar._meta.get_field('a').remote_field.related_name
self.assertIsInstance(rel_name, str)
def test_abstract_model_pending_operations(self):
"""
Foreign key fields declared on abstract models should not add lazy
relations to resolve relationship declared as string (#24215).
"""
pending_ops_before = list(apps._pending_operations.items())
class AbstractForeignKeyModel(models.Model):
fk = models.ForeignKey('missing.FK', models.CASCADE)
class Meta:
abstract = True
self.assertIs(AbstractForeignKeyModel._meta.apps, apps)
self.assertEqual(
pending_ops_before,
list(apps._pending_operations.items()),
'Pending lookup added for a foreign key on an abstract model'
)
@isolate_apps('model_fields', 'model_fields.tests')
def test_abstract_model_app_relative_foreign_key(self):
class AbstractReferent(models.Model):
reference = models.ForeignKey('Referred', on_delete=models.CASCADE)
class Meta:
app_label = 'model_fields'
abstract = True
def assert_app_model_resolved(label):
class Referred(models.Model):
class Meta:
app_label = label
class ConcreteReferent(AbstractReferent):
class Meta:
app_label = label
self.assertEqual(ConcreteReferent._meta.get_field('reference').related_model, Referred)
assert_app_model_resolved('model_fields')
assert_app_model_resolved('tests')
@isolate_apps('model_fields')
def test_to_python(self):
class Foo(models.Model):
pass
class Bar(models.Model):
fk = models.ForeignKey(Foo, models.CASCADE)
self.assertEqual(Bar._meta.get_field('fk').to_python('1'), 1)
@isolate_apps('model_fields')
def test_fk_to_fk_get_col_output_field(self):
class Foo(models.Model):
pass
class Bar(models.Model):
foo = models.ForeignKey(Foo, models.CASCADE, primary_key=True)
class Baz(models.Model):
bar = models.ForeignKey(Bar, models.CASCADE, primary_key=True)
col = Baz._meta.get_field('bar').get_col('alias')
self.assertIs(col.output_field, Foo._meta.pk)
@isolate_apps('model_fields')
def test_recursive_fks_get_col(self):
class Foo(models.Model):
bar = models.ForeignKey('Bar', models.CASCADE, primary_key=True)
class Bar(models.Model):
foo = models.ForeignKey(Foo, models.CASCADE, primary_key=True)
with self.assertRaisesMessage(ValueError, 'Cannot resolve output_field'):
Foo._meta.get_field('bar').get_col('alias')