[pull] main from django:main

AUTHORS

@@ -916,6 +916,7 @@ answer newbie questions, and generally made Django that much better:
     Rob Hudson <https://rob.cogit8.org/>
     Rob Nguyen <tienrobertnguyenn@gmail.com>
     Robin Munn <http://www.geekforgod.com/>
+    Rodrigo Bastos Vieira <rodrigo.vieira@gmail.com>
     Rodrigo Pinheiro Marques de Araújo <fenrrir@gmail.com>
     Roel Delos Reyes <https://roelzkie.dev>
     Rohith P R <https://rohithpr.com>

django/forms/models.py

@@ -776,8 +776,9 @@ def get_queryset(self):
             # If the queryset isn't already ordered we need to add an
             # artificial ordering here to make sure that all formsets
             # constructed from this queryset have the same form order.
-            if not qs.ordered:
-                qs = qs.order_by(self.model._meta.pk.name)
+            if not qs.totally_ordered:
+                current_ordering = qs.query.order_by or qs.model._meta.ordering or []
+                qs = qs.order_by(*current_ordering, "pk")
 
             # Removed queryset limiting here. As per discussion re: #13023
             # on django-dev, max_num should not prevent existing

tests/model_formsets/tests.py

@@ -1773,6 +1773,46 @@ def test_model_formset_with_initial_queryset(self):
         formset = FormSet(initial=[{"authors": Author.objects.all()}], data=data)
         self.assertFalse(formset.extra_forms[0].has_changed())
 
+    def test_get_queryset_falls_back_to_pk_when_no_ordering_defined(self):
+        # Product has no Meta.ordering, so the default queryset is not
+        # totally ordered.
+        self.assertIs(Product._default_manager.get_queryset().totally_ordered, False)
+
+        ProductFormSet = modelformset_factory(Product, fields="__all__")
+        formset = ProductFormSet()
+
+        queryset = formset.get_queryset()
+        self.assertEqual(queryset.query.order_by, ("pk",))
+
+    def test_get_queryset_appends_pk_to_explicit_queryset_ordering(self):
+        # Author.name is non-unique, so order_by("name") is not totally
+        # ordered.
+        AuthorFormSet = modelformset_factory(Author, fields="__all__")
+        formset = AuthorFormSet(queryset=Author.objects.order_by("name"))
+
+        queryset = formset.get_queryset()
+        self.assertEqual(queryset.query.order_by, ("name", "pk"))
+
+    def test_get_queryset_appends_pk_to_meta_ordering(self):
+        # Author has Meta.ordering = ("name",) which is not deterministic
+        # by itself.
+        AuthorFormSet = modelformset_factory(Author, fields="__all__")
+        formset = AuthorFormSet()
+
+        queryset = formset.get_queryset()
+        self.assertEqual(queryset.query.order_by, ("name", "pk"))
+
+    def test_get_queryset_unchanged_when_already_totally_ordered(self):
+        # Ordering by pk is already totally ordered; pk must not be
+        # appended again.
+        AuthorFormSet = modelformset_factory(Author, fields="__all__")
+        formset = AuthorFormSet(queryset=Author.objects.order_by("pk"))
+
+        queryset = formset.get_queryset()
+        # Must be exactly ("pk",), not ("pk", "pk").
+        self.assertEqual(queryset.query.order_by, ("pk",))
+        self.assertIs(queryset.totally_ordered, True)
+
     def test_prevent_duplicates_from_with_the_same_formset(self):
         FormSet = modelformset_factory(Product, fields="__all__", extra=2)
         data = {