Fixed #13312 -- Allowed specifying the order of null fields in queries.

Thanks Mariusz Felisiak for finishing the patch.

2 files changed, 52 insertions, 2 deletions

diff --git a/tests/ordering/models.py b/tests/ordering/models.py
index 2c4e9b3308..1f794ca3a1 100644
--- a/tests/ordering/models.py
+++ b/tests/ordering/models.py
@@ -18,6 +18,8 @@ from django.utils.encoding import python_2_unicode_compatible
 
 
 class Author(models.Model):
+    name = models.CharField(max_length=63, null=True, blank=True)
+
     class Meta:
         ordering = ('-pk',)
 
diff --git a/tests/ordering/tests.py b/tests/ordering/tests.py
index f19cbdeddc..399b8d7035 100644
--- a/tests/ordering/tests.py
+++ b/tests/ordering/tests.py
@@ -4,6 +4,7 @@ from datetime import datetime
 from operator import attrgetter
 
 from django.db.models import F
+from django.db.models.functions import Upper
 from django.test import TestCase
 
 from .models import Article, Author, Reference
@@ -17,8 +18,8 @@ class OrderingTests(TestCase):
         cls.a2 = Article.objects.create(headline="Article 2", pub_date=datetime(2005, 7, 27))
         cls.a3 = Article.objects.create(headline="Article 3", pub_date=datetime(2005, 7, 27))
         cls.a4 = Article.objects.create(headline="Article 4", pub_date=datetime(2005, 7, 28))
-        cls.author_1 = Author.objects.create()
-        cls.author_2 = Author.objects.create()
+        cls.author_1 = Author.objects.create(name="Name 1")
+        cls.author_2 = Author.objects.create(name="Name 2")
         for i in range(2):
             Author.objects.create()
 
@@ -88,6 +89,53 @@ class OrderingTests(TestCase):
             attrgetter("headline")
         )
 
+    def test_order_by_nulls_first_and_last(self):
+        msg = "nulls_first and nulls_last are mutually exclusive"
+        with self.assertRaisesMessage(ValueError, msg):
+            Article.objects.order_by(F("author").desc(nulls_last=True, nulls_first=True))
+
+    def test_order_by_nulls_last(self):
+        Article.objects.filter(headline="Article 3").update(author=self.author_1)
+        Article.objects.filter(headline="Article 4").update(author=self.author_2)
+        # asc and desc are chainable with nulls_last.
+        self.assertSequenceEqual(
+            Article.objects.order_by(F("author").desc(nulls_last=True)),
+            [self.a4, self.a3, self.a1, self.a2],
+        )
+        self.assertSequenceEqual(
+            Article.objects.order_by(F("author").asc(nulls_last=True)),
+            [self.a3, self.a4, self.a1, self.a2],
+        )
+        self.assertSequenceEqual(
+            Article.objects.order_by(Upper("author__name").desc(nulls_last=True)),
+            [self.a4, self.a3, self.a1, self.a2],
+        )
+        self.assertSequenceEqual(
+            Article.objects.order_by(Upper("author__name").asc(nulls_last=True)),
+            [self.a3, self.a4, self.a1, self.a2],
+        )
+
+    def test_order_by_nulls_first(self):
+        Article.objects.filter(headline="Article 3").update(author=self.author_1)
+        Article.objects.filter(headline="Article 4").update(author=self.author_2)
+        # asc and desc are chainable with nulls_first.
+        self.assertSequenceEqual(
+            Article.objects.order_by(F("author").asc(nulls_first=True)),
+            [self.a1, self.a2, self.a3, self.a4],
+        )
+        self.assertSequenceEqual(
+            Article.objects.order_by(F("author").desc(nulls_first=True)),
+            [self.a1, self.a2, self.a4, self.a3],
+        )
+        self.assertSequenceEqual(
+            Article.objects.order_by(Upper("author__name").asc(nulls_first=True)),
+            [self.a1, self.a2, self.a3, self.a4],
+        )
+        self.assertSequenceEqual(
+            Article.objects.order_by(Upper("author__name").desc(nulls_first=True)),
+            [self.a1, self.a2, self.a4, self.a3],
+        )
+
     def test_stop_slicing(self):
         """
         Use the 'stop' part of slicing notation to limit the results.