Fixed #33018 -- Fixed annotations with empty queryset.

Thanks Simon Charette for the review and implementation idea.

2 files changed, 18 insertions, 1 deletions

diff --git a/tests/annotations/tests.py b/tests/annotations/tests.py
index c0fe308a07..62912ee99c 100644
--- a/tests/annotations/tests.py
+++ b/tests/annotations/tests.py
@@ -210,6 +210,12 @@ class NonAggregateAnnotationTestCase(TestCase):
         self.assertEqual(len(books), Book.objects.count())
         self.assertTrue(all(not book.selected for book in books))
 
+    def test_empty_queryset_annotation(self):
+        qs = Author.objects.annotate(
+            empty=Subquery(Author.objects.values('id').none())
+        )
+        self.assertIsNone(qs.first().empty)
+
     def test_annotate_with_aggregation(self):
         books = Book.objects.annotate(is_book=Value(1), rating_count=Count('rating'))
         for book in books:
diff --git a/tests/db_functions/comparison/test_coalesce.py b/tests/db_functions/comparison/test_coalesce.py
index 8ba4b01fe6..1093079d68 100644
--- a/tests/db_functions/comparison/test_coalesce.py
+++ b/tests/db_functions/comparison/test_coalesce.py
@@ -1,4 +1,4 @@
-from django.db.models import TextField
+from django.db.models import Subquery, TextField
 from django.db.models.functions import Coalesce, Lower
 from django.test import TestCase
 from django.utils import timezone
@@ -70,3 +70,14 @@ class CoalesceTests(TestCase):
             authors, ['John Smith', 'Rhonda'],
             lambda a: a.name
         )
+
+    def test_empty_queryset(self):
+        Author.objects.create(name='John Smith')
+        tests = [
+            Author.objects.none(),
+            Subquery(Author.objects.none()),
+        ]
+        for empty_query in tests:
+            with self.subTest(empty_query.__class__.__name__):
+                qs = Author.objects.annotate(annotation=Coalesce(empty_query, 42))
+                self.assertEqual(qs.first().annotation, 42)