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from unittest import skipUnless
from django.db import connection
from django.db.models import Value
from django.db.models.functions import NullIf
from django.test import TestCase
from ..models import Author
class NullIfTests(TestCase):
@classmethod
def setUpTestData(cls):
Author.objects.create(name="John Smith", alias="smithj")
Author.objects.create(name="Rhonda", alias="Rhonda")
def test_basic(self):
authors = Author.objects.annotate(nullif=NullIf("alias", "name")).values_list(
"nullif"
)
self.assertCountEqual(
authors,
[
("smithj",),
(
(
""
if connection.features.interprets_empty_strings_as_nulls
else None
),
),
],
)
def test_null_argument(self):
authors = Author.objects.annotate(
nullif=NullIf("name", Value(None))
).values_list("nullif")
self.assertCountEqual(authors, [("John Smith",), ("Rhonda",)])
def test_too_few_args(self):
msg = "'NullIf' takes exactly 2 arguments (1 given)"
with self.assertRaisesMessage(TypeError, msg):
NullIf("name")
@skipUnless(connection.vendor == "oracle", "Oracle specific test for NULL-literal")
def test_null_literal(self):
msg = "Oracle does not allow Value(None) for expression1."
with self.assertRaisesMessage(ValueError, msg):
list(
Author.objects.annotate(nullif=NullIf(Value(None), "name")).values_list(
"nullif"
)
)
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