Fixed #36288 -- Addressed improper handling of duplicates in values_list().

Now that selected aliases are stored in sql.Query.selected: dict[str, Any]
the values_list() method must ensures that duplicate field name references are
assigned unique aliases.

Refs #28900.

Regression in 65ad4ade74dc9208b9d686a451cd6045df0c9c3a.

Thanks Claude for the report.

django/db/models/query.py

@@ -1371,24 +1371,33 @@ class QuerySet(AltersData):
                 "field."
             )
 
-        field_names = {f for f in fields if not hasattr(f, "resolve_expression")}
+        field_names = {f: False for f in fields if not hasattr(f, "resolve_expression")}
         _fields = []
         expressions = {}
         counter = 1
         for field in fields:
+            field_name = field
+            expression = None
             if hasattr(field, "resolve_expression"):
-                field_id_prefix = getattr(
+                field_name = getattr(
                     field, "default_alias", field.__class__.__name__.lower()
                 )
-                while True:
-                    field_id = field_id_prefix + str(counter)
+                expression = field
+                # For backward compatibility reasons expressions are always
+                # prefixed with the counter even if their default alias doesn't
+                # collide with field names. Changing this logic could break
+                # some usage of named=True.
+                seen = True
+            elif seen := field_names[field_name]:
+                expression = F(field_name)
+            if seen:
+                field_name_prefix = field_name
+                while (field_name := f"{field_name_prefix}{counter}") in field_names:
                     counter += 1
-                    if field_id not in field_names:
-                        break
-                expressions[field_id] = field
-                _fields.append(field_id)
-            else:
-                _fields.append(field)
+            if expression is not None:
+                expressions[field_name] = expression
+            field_names[field_name] = True
+            _fields.append(field_name)
 
         clone = self._values(*_fields, **expressions)
         clone._iterable_class = (

docs/releases/5.2.1.txt

@@ -32,3 +32,7 @@ Bugfixes
 * Fixed a regression in Django 5.2 that caused a crash when using
   ``QuerySet.select_for_update(of=(…))`` with ``values()/values_list()``
   including expressions (:ticket:`36301`).
+
+* Fixed a regression in Django 5.2 that caused improper values to be returned
+  from ``QuerySet.values_list()`` when duplicate field names were specified
+  (:ticket:`36288`).

tests/composite_pk/test_values.py

@@ -128,18 +128,18 @@ class CompositePKValuesTests(TestCase):
             self.assertSequenceEqual(
                 User.objects.values_list("pk", "pk").order_by("pk"),
                 (
-                    (self.user_1.pk,),
-                    (self.user_2.pk,),
-                    (self.user_3.pk,),
+                    (self.user_1.pk, self.user_1.pk),
+                    (self.user_2.pk, self.user_2.pk),
+                    (self.user_3.pk, self.user_3.pk),
                 ),
             )
         with self.subTest('User.objects.values_list("pk", "id", "pk", "id")'):
             self.assertSequenceEqual(
                 User.objects.values_list("pk", "id", "pk", "id").order_by("pk"),
                 (
-                    (self.user_1.pk, self.user_1.id),
-                    (self.user_2.pk, self.user_2.id),
-                    (self.user_3.pk, self.user_3.id),
+                    (self.user_1.pk, self.user_1.id, self.user_1.pk, self.user_1.id),
+                    (self.user_2.pk, self.user_2.id, self.user_2.pk, self.user_2.id),
+                    (self.user_3.pk, self.user_3.id, self.user_3.pk, self.user_3.id),
                 ),
             )
 

tests/queries/tests.py

@@ -2668,6 +2668,12 @@ class ValuesQuerysetTests(TestCase):
         qs = qs.values_list("num", flat=True)
         self.assertSequenceEqual(qs, [72])
 
+    def test_duplicate_values_list(self):
+        value = Number.objects.values_list("num", "num").get()
+        self.assertEqual(value, (72, 72))
+        value = Number.objects.values_list(F("num"), F("num")).get()
+        self.assertEqual(value, (72, 72))
+
     def test_extra_values(self):
         # testing for ticket 14930 issues
         qs = Number.objects.extra(