[5.0.x] Fixed #35350 -- Fixed save() with pk set on models with GeneratedFields.

Thanks Matt Hegarty for the report and Simon Charette and Natalia Bidart for the reviews.

Regression in f333e35.

Backport of 8b53560eea9f10a1271d3bdf765dc6f969c7d9d5 from main.

django/db/models/base.py

@@ -993,12 +993,16 @@ class Model(AltersData, metaclass=ModelBase):
         for a single table.
         """
         meta = cls._meta
-        non_pks = [f for f in meta.local_concrete_fields if not f.primary_key]
+        non_pks_non_generated = [
+            f
+            for f in meta.local_concrete_fields
+            if not f.primary_key and not f.generated
+        ]
 
         if update_fields:
-            non_pks = [
+            non_pks_non_generated = [
                 f
-                for f in non_pks
+                for f in non_pks_non_generated
                 if f.name in update_fields or f.attname in update_fields
             ]
 
@@ -1030,7 +1034,7 @@ class Model(AltersData, metaclass=ModelBase):
                     None,
                     (getattr(self, f.attname) if raw else f.pre_save(self, False)),
                 )
-                for f in non_pks
+                for f in non_pks_non_generated
             ]
             forced_update = update_fields or force_update
             updated = self._do_update(

docs/releases/5.0.5.txt

@@ -9,4 +9,6 @@ Django 5.0.5 fixes several bugs in 5.0.4.
 Bugfixes
 ========
 
-* ...
+* Fixed a bug in Django 5.0 that caused a crash of ``Model.save()`` when
+  creating an instance of a model with a ``GeneratedField`` and providing a
+  primary key (:ticket:`35350`).

tests/model_fields/test_generatedfield.py

@@ -207,6 +207,12 @@ class GeneratedFieldTestMixin:
         m.refresh_from_db()
         self.assertEqual(m.field, 8)
 
+    def test_save_model_with_pk(self):
+        m = self.base_model(pk=1, a=1, b=2)
+        m.save()
+        m = self._refresh_if_needed(m)
+        self.assertEqual(m.field, 3)
+
     def test_save_model_with_foreign_key(self):
         fk_object = Foo.objects.create(a="abc", d=Decimal("12.34"))
         m = self.base_model(a=1, b=2, fk=fk_object)