[5.1.x] Fixed #35554, Refs #35060 -- Corrected deprecated *args parsing in Model.save()/asave().

The transitional logic added to deprecate the usage of *args for
Model.save()/asave() introduced two issues that this branch fixes:
 * Passing extra positional arguments no longer raised TypeError.
 * Passing a positional but empty update_fields would save all fields.

Co-authored-by: Natalia <124304+nessita@users.noreply.github.com>

Backport of 28522c3c8d from main.

django/db/models/base.py

@@ -803,18 +803,20 @@ class Model(AltersData, metaclass=ModelBase):
                 RemovedInDjango60Warning,
                 stacklevel=2,
             )
-            for arg, attr in zip(
-                args, ["force_insert", "force_update", "using", "update_fields"]
-            ):
-                if arg:
-                    if attr == "force_insert":
-                        force_insert = arg
-                    elif attr == "force_update":
-                        force_update = arg
-                    elif attr == "using":
-                        using = arg
-                    else:
-                        update_fields = arg
+            total_len_args = len(args) + 1  # include self
+            if total_len_args > 5:
+                # Recreate the proper TypeError message from Python.
+                raise TypeError(
+                    "Model.save() takes from 1 to 5 positional arguments but "
+                    f"{total_len_args} were given"
+                )
+            force_insert = args[0]
+            try:
+                force_update = args[1]
+                using = args[2]
+                update_fields = args[3]
+            except IndexError:
+                pass
 
         self._prepare_related_fields_for_save(operation_name="save")
 
@@ -888,18 +890,20 @@ class Model(AltersData, metaclass=ModelBase):
                 RemovedInDjango60Warning,
                 stacklevel=2,
             )
-            for arg, attr in zip(
-                args, ["force_insert", "force_update", "using", "update_fields"]
-            ):
-                if arg:
-                    if attr == "force_insert":
-                        force_insert = arg
-                    elif attr == "force_update":
-                        force_update = arg
-                    elif attr == "using":
-                        using = arg
-                    else:
-                        update_fields = arg
+            total_len_args = len(args) + 1  # include self
+            if total_len_args > 5:
+                # Recreate the proper TypeError message from Python.
+                raise TypeError(
+                    "Model.asave() takes from 1 to 5 positional arguments but "
+                    f"{total_len_args} were given"
+                )
+            force_insert = args[0]
+            try:
+                force_update = args[1]
+                using = args[2]
+                update_fields = args[3]
+            except IndexError:
+                pass
 
         return await sync_to_async(self.save)(
             force_insert=force_insert,

tests/basic/tests.py

@@ -210,6 +210,35 @@ class ModelInstanceCreationTests(TestCase):
             a.save(False, False, None, None)
             self.assertEqual(Article.objects.count(), 1)
 
+    def test_save_deprecation_positional_arguments_used(self):
+        a = Article()
+        fields = ["headline"]
+        with (
+            self.assertWarns(RemovedInDjango60Warning),
+            mock.patch.object(a, "save_base") as mock_save_base,
+        ):
+            a.save(None, 1, 2, fields)
+        self.assertEqual(
+            mock_save_base.mock_calls,
+            [
+                mock.call(
+                    using=2,
+                    force_insert=None,
+                    force_update=1,
+                    update_fields=frozenset(fields),
+                )
+            ],
+        )
+
+    def test_save_too_many_positional_arguments(self):
+        a = Article()
+        msg = "Model.save() takes from 1 to 5 positional arguments but 6 were given"
+        with (
+            self.assertWarns(RemovedInDjango60Warning),
+            self.assertRaisesMessage(TypeError, msg),
+        ):
+            a.save(False, False, None, None, None)
+
     async def test_asave_deprecation(self):
         a = Article(headline="original", pub_date=datetime(2014, 5, 16))
         msg = "Passing positional arguments to asave() is deprecated"
@@ -217,6 +246,35 @@ class ModelInstanceCreationTests(TestCase):
             await a.asave(False, False, None, None)
             self.assertEqual(await Article.objects.acount(), 1)
 
+    async def test_asave_deprecation_positional_arguments_used(self):
+        a = Article()
+        fields = ["headline"]
+        with (
+            self.assertWarns(RemovedInDjango60Warning),
+            mock.patch.object(a, "save_base") as mock_save_base,
+        ):
+            await a.asave(None, 1, 2, fields)
+        self.assertEqual(
+            mock_save_base.mock_calls,
+            [
+                mock.call(
+                    using=2,
+                    force_insert=None,
+                    force_update=1,
+                    update_fields=frozenset(fields),
+                )
+            ],
+        )
+
+    async def test_asave_too_many_positional_arguments(self):
+        a = Article()
+        msg = "Model.asave() takes from 1 to 5 positional arguments but 6 were given"
+        with (
+            self.assertWarns(RemovedInDjango60Warning),
+            self.assertRaisesMessage(TypeError, msg),
+        ):
+            await a.asave(False, False, None, None, None)
+
     @ignore_warnings(category=RemovedInDjango60Warning)
     def test_save_positional_arguments(self):
         a = Article.objects.create(headline="original", pub_date=datetime(2014, 5, 16))

tests/update_only_fields/tests.py

@@ -1,5 +1,6 @@
 from django.db.models.signals import post_save, pre_save
 from django.test import TestCase
+from django.utils.deprecation import RemovedInDjango60Warning
 
 from .models import Account, Employee, Person, Profile, ProxyEmployee
 
@@ -256,6 +257,29 @@ class UpdateOnlyFieldsTests(TestCase):
         pre_save.disconnect(pre_save_receiver)
         post_save.disconnect(post_save_receiver)
 
+    def test_empty_update_fields_positional_save(self):
+        s = Person.objects.create(name="Sara", gender="F")
+
+        msg = "Passing positional arguments to save() is deprecated"
+        with (
+            self.assertWarnsMessage(RemovedInDjango60Warning, msg),
+            self.assertNumQueries(0),
+        ):
+            s.save(False, False, None, [])
+
+    async def test_empty_update_fields_positional_asave(self):
+        s = await Person.objects.acreate(name="Sara", gender="F")
+        # Workaround for a lack of async assertNumQueries.
+        s.name = "Other"
+
+        msg = "Passing positional arguments to asave() is deprecated"
+        with self.assertWarnsMessage(RemovedInDjango60Warning, msg):
+            await s.asave(False, False, None, [])
+
+        # No save occurred for an empty update_fields.
+        await s.arefresh_from_db()
+        self.assertEqual(s.name, "Sara")
+
     def test_num_queries_inheritance(self):
         s = Employee.objects.create(name="Sara", gender="F")
         s.employee_num = 1