Fixed #29049 -- Added slicing notation to F expressions.

Co-authored-by: Priyansh Saxena <askpriyansh@gmail.com>
Co-authored-by: Niclas Olofsson <n@niclasolofsson.se>
Co-authored-by: David Smith <smithdc@gmail.com>
Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Co-authored-by: Abhinav Yadav <abhinav.sny.2002@gmail.com>

1 files changed, 35 insertions, 1 deletions

diff --git a/tests/postgres_tests/test_array.py b/tests/postgres_tests/test_array.py
index 8aaa7be077..386a0afa3a 100644
--- a/tests/postgres_tests/test_array.py
+++ b/tests/postgres_tests/test_array.py
@@ -10,7 +10,7 @@ from django.core import checks, exceptions, serializers, validators
 from django.core.exceptions import FieldError
 from django.core.management import call_command
 from django.db import IntegrityError, connection, models
-from django.db.models.expressions import Exists, OuterRef, RawSQL, Value
+from django.db.models.expressions import Exists, F, OuterRef, RawSQL, Value
 from django.db.models.functions import Cast, JSONObject, Upper
 from django.test import TransactionTestCase, override_settings, skipUnlessDBFeature
 from django.test.utils import isolate_apps
@@ -594,6 +594,40 @@ class TestQuerying(PostgreSQLTestCase):
             [None, [1], [2], [2, 3], [20, 30]],
         )
 
+    def test_slicing_of_f_expressions(self):
+        tests = [
+            (F("field")[:2], [1, 2]),
+            (F("field")[2:], [3, 4]),
+            (F("field")[1:3], [2, 3]),
+            (F("field")[3], [4]),
+            (F("field")[:3][1:], [2, 3]),  # Nested slicing.
+            (F("field")[:3][1], [2]),  # Slice then index.
+        ]
+        for expression, expected in tests:
+            with self.subTest(expression=expression, expected=expected):
+                instance = IntegerArrayModel.objects.create(field=[1, 2, 3, 4])
+                instance.field = expression
+                instance.save()
+                instance.refresh_from_db()
+                self.assertEqual(instance.field, expected)
+
+    def test_slicing_of_f_expressions_with_annotate(self):
+        IntegerArrayModel.objects.create(field=[1, 2, 3])
+        annotated = IntegerArrayModel.objects.annotate(
+            first_two=F("field")[:2],
+            after_two=F("field")[2:],
+            random_two=F("field")[1:3],
+        ).get()
+        self.assertEqual(annotated.first_two, [1, 2])
+        self.assertEqual(annotated.after_two, [3])
+        self.assertEqual(annotated.random_two, [2, 3])
+
+    def test_slicing_of_f_expressions_with_len(self):
+        queryset = NullableIntegerArrayModel.objects.annotate(
+            subarray=F("field")[:1]
+        ).filter(field__len=F("subarray__len"))
+        self.assertSequenceEqual(queryset, self.objs[:2])
+
     def test_usage_in_subquery(self):
         self.assertSequenceEqual(
             NullableIntegerArrayModel.objects.filter(