Improve refresh_from_db to make it works with protected fields

Author: pfouque

django_fsm/__init__.py

@@ -431,19 +431,16 @@ def is_fsm_and_protected(f):
         return {f.attname for f in protected_fields}
 
     def refresh_from_db(self, *args, **kwargs):
-        fields = kwargs.pop("fields", None)
+        protected_fields = self._get_protected_fsm_fields()
 
-        # Use provided fields, if not set then reload all non-deferred fields.0
-        if not fields:
-            deferred_fields = self.get_deferred_fields()
-            protected_fields = self._get_protected_fsm_fields()
-            skipped_fields = deferred_fields.union(protected_fields)
+        for f in protected_fields:
+            self._meta.get_field(f).protected = False
 
-            fields = [f.attname for f in self._meta.concrete_fields if f.attname not in skipped_fields]
-
-        kwargs["fields"] = fields
         super().refresh_from_db(*args, **kwargs)
 
+        for f in protected_fields:
+            self._meta.get_field(f).protected = True
+
 
 class ConcurrentTransitionMixin:
     """

tests/testapp/tests/test_protected_fields.py

@@ -26,18 +26,33 @@ def test_no_direct_access(self):
         instance = RefreshableProtectedAccessModel()
         assert instance.status == "new"
 
-        def try_change():
-            instance.status = "change"
-
         with pytest.raises(AttributeError):
-            try_change()
+            instance.status = "change"
 
         instance.publish()
         instance.save()
         assert instance.status == "published"
 
     def test_refresh_from_db(self):
         instance = RefreshableModel()
+        assert instance.status == "new"
+        instance.save()
+
+        instance.refresh_from_db()
+        assert instance.status == "new"
+
+    def test_concurrent_refresh_from_db(self):
+        instance = RefreshableModel()
+        assert instance.status == "new"
         instance.save()
 
+        # NOTE: This simulates a concurrent update scenario
+        concurrent_instance = RefreshableModel.objects.get(pk=instance.pk)
+        assert concurrent_instance.status == instance.status == "new"
+        concurrent_instance.publish()
+        assert concurrent_instance.status == "published"
+        concurrent_instance.save()
+
+        assert instance.status == "new"
         instance.refresh_from_db()
+        assert instance.status == "published"