Fixed #32210 -- Fixed model inlines with to_field that has a default.

django/forms/models.py

@@ -1177,7 +1177,13 @@ class BaseInlineFormSet(BaseModelFormSet):
                 to_field = self.instance._meta.get_field(kwargs["to_field"])
             else:
                 to_field = self.instance._meta.pk
-            if to_field.has_default():
+
+            if to_field.has_default() and (
+                # Don't ignore a parent's auto-generated key if it's not the
+                # parent model's pk and form data is provided.
+                to_field.attname == self.fk.remote_field.model._meta.pk.name
+                or not form.data
+            ):
                 setattr(self.instance, to_field.attname, None)
 
         form.fields[name] = InlineForeignKeyField(self.instance, **kwargs)

tests/model_formsets/test_uuid.py

@@ -93,3 +93,25 @@ class InlineFormsetTests(TestCase):
         )
         formset = FormSet()
         self.assertIsNone(formset.forms[0].fields["parent"].initial)
+
+    def test_inlineformset_factory_nulls_default_pks_alternate_key_relation_data(self):
+        """
+        If form data is provided, a parent's auto-generated alternate key is
+        set.
+        """
+        FormSet = inlineformset_factory(
+            ParentWithUUIDAlternateKey, ChildRelatedViaAK, fields="__all__"
+        )
+        formset = FormSet(
+            {
+                "childrelatedviaak_set-TOTAL_FORMS": 3,
+                "childrelatedviaak_set-INITIAL_FORMS": 0,
+                "childrelatedviaak_set-MAX_NUM_FORMS": "",
+                "childrelatedviaak_set-0-name": "Test",
+                "childrelatedviaak_set-1-name": "",
+                "childrelatedviaak_set-2-name": "",
+            }
+        )
+        self.assertIs(formset.is_valid(), True)
+        self.assertIsNotNone(formset.instance.uuid)
+        self.assertEqual(formset.forms[0].instance.parent_id, formset.instance.uuid)