Address PR feedback

Author: andystaples

CHANGELOG.md

@@ -61,6 +61,13 @@ CHANGED
 - JSON serialization failures now raise a `TypeError` that chains the original
   error (`__cause__`) and names the offending type.
 
+FIXED
+
+- Falsy entity states (`0`, `""`, `[]`, `{}`) are no longer dropped when an
+  entity batch is persisted. Previously a falsy current state was treated as
+  "no state" and written as `None`, effectively deleting it; only an actual
+  `None` state now clears the persisted entity state.
+
 BREAKING CHANGES (type-level only — no runtime impact for typical users)
 
 These changes do not alter runtime behavior, but because the package ships

durabletask/task.py

@@ -181,6 +181,7 @@ def call_entity(self,
                     entity: EntityInstanceId,
                     operation: str,
                     input: Any = ...,
+                    *,
                     return_type: None = ...) -> CompletableTask[Any]:
         ...
 
@@ -189,6 +190,7 @@ def call_entity(self,
                     entity: EntityInstanceId,
                     operation: str,
                     input: Any = None,
+                    *,
                     return_type: type | None = None) -> CompletableTask[Any]:
         """Schedule entity function for execution.
 

durabletask/worker.py

@@ -1376,7 +1376,7 @@ def _execute_entity_batch(
         batch_result = pb.EntityBatchResult(
             results=results,
             actions=entity_state.get_operation_actions(),
-            entityState=helpers.get_string_value(self._data_converter.serialize(entity_state._current_state)) if entity_state._current_state else None,  # pyright: ignore[reportPrivateUsage]
+            entityState=helpers.get_string_value(self._data_converter.serialize(entity_state._current_state)) if entity_state._current_state is not None else None,  # pyright: ignore[reportPrivateUsage]
             failureDetails=None,
             completionToken=completionToken,
             operationInfos=operation_infos,
@@ -1716,6 +1716,7 @@ def call_entity(
             entity: EntityInstanceId,
             operation: str,
             input: Any = ...,
+            *,
             return_type: None = ...,
     ) -> task.CompletableTask[Any]:
         ...
@@ -1725,6 +1726,7 @@ def call_entity(
             entity: EntityInstanceId,
             operation: str,
             input: Any = None,
+            *,
             return_type: type | None = None,
     ) -> task.CompletableTask[Any]:
         id = self.next_sequence_number()

tests/durabletask/test_batch_actions.py

@@ -385,6 +385,41 @@ def counter_entity(ctx: entities.EntityContext, input):
         worker.stop()
 
 
+def test_entity_falsy_state_is_persisted(backend):
+    """A falsy entity state (e.g. 0) must be persisted, not dropped as None.
+
+    Regression test: the batch result previously persisted state only when it
+    was truthy, so a valid falsy state such as ``0`` was written as ``None`` and
+    effectively deleted. Only an actual ``None`` should clear the state.
+    """
+    def counter_entity(ctx: entities.EntityContext, input):
+        if ctx.operation == "set":
+            ctx.set_state(input)
+        elif ctx.operation == "get":
+            return ctx.get_state(int)
+
+    worker = TaskHubGrpcWorker(host_address=HOST)
+
+    worker.add_entity(counter_entity)
+    worker.start()
+
+    try:
+        with TaskHubGrpcClient(host_address=HOST) as c:
+            entity_id = entities.EntityInstanceId("counter_entity", "falsyCounter")
+            # Set the state to a falsy-but-valid value.
+            c.signal_entity(entity_id, "set", input=0)
+            time.sleep(3)  # Wait for the signal to be processed
+
+            query = client.EntityQuery(include_state=True)
+            all_entities = c.get_all_entities(query)
+            matches = [e for e in all_entities if e.id == entity_id]
+            # The entity must still exist with its falsy state intact.
+            assert len(matches) == 1
+            assert matches[0].get_state(int) == 0
+    finally:
+        worker.stop()
+
+
 def test_get_entities_by_instance_id_prefix(backend):
     def counter_entity(ctx: entities.EntityContext, input):
         if ctx.operation == "set":