fix(idempotency): idempotent_function should support standalone falsy values (#1669)

Author: heitorlessa

Diff for: aws_lambda_powertools/utilities/idempotency/idempotency.py

@@ -134,14 +134,14 @@ def decorate(*args, **kwargs):
         if os.getenv(constants.IDEMPOTENCY_DISABLED_ENV):
             return function(*args, **kwargs)
 
-        payload = kwargs.get(data_keyword_argument)
-
-        if not payload:
+        if data_keyword_argument not in kwargs:
             raise RuntimeError(
                 f"Unable to extract '{data_keyword_argument}' from keyword arguments."
                 f" Ensure this exists in your function's signature as well as the caller used it as a keyword argument"
             )
 
+        payload = kwargs.get(data_keyword_argument)
+
         idempotency_handler = IdempotencyHandler(
             function=function,
             function_payload=payload,

Diff for: tests/functional/idempotency/test_idempotency.py

@@ -72,7 +72,7 @@ def test_idempotent_lambda_already_completed(
     lambda_context,
 ):
     """
-    Test idempotent decorator where event with matching event key has already been succesfully processed
+    Test idempotent decorator where event with matching event key has already been successfully processed
     """
 
     stubber = stub.Stubber(persistence_store.table.meta.client)
@@ -1247,6 +1247,46 @@ def lambda_handler(event, _):
     assert handler_result == expected_result
 
 
+@pytest.mark.parametrize("data", [None, 0, False])
+def test_idempotent_function_falsy_values(data):
+    # Scenario to validate we can use idempotent_function with any function
+    # receiving a falsy value (`None`, `False`, `0`, etc.)
+    # shouldn't cause a RuntimeError
+    mock_event = data
+    idempotency_key = f"{TESTS_MODULE_PREFIX}.test_idempotent_function_falsy_values.<locals>.record_handler#{hash_idempotency_key(mock_event)}"  # noqa: E501
+
+    persistence_layer = MockPersistenceLayer(expected_idempotency_key=idempotency_key)
+    expected_result = {"message": "Foo"}
+
+    @idempotent_function(persistence_store=persistence_layer, data_keyword_argument="record")
+    def record_handler(record):
+        return expected_result
+
+    # WHEN calling the function
+    result = record_handler(record=mock_event)
+    # THEN we expect the function to execute successfully
+    assert result == expected_result
+
+
+@pytest.mark.parametrize("data", [None, 0, False])
+def test_idempotent_function_falsy_values_with_raise_on_no_idempotency_key(
+    data, persistence_store: DynamoDBPersistenceLayer
+):
+    # GIVEN raise_on_no_idempotency_key is True
+    idempotency_config = IdempotencyConfig(event_key_jmespath="idemKey", raise_on_no_idempotency_key=True)
+
+    @idempotent_function(data_keyword_argument="record", persistence_store=persistence_store, config=idempotency_config)
+    def record_handler(record):
+        return ValueError("Should not be raised")
+
+    # WHEN calling the function
+    with pytest.raises(IdempotencyKeyError) as e:
+        record_handler(record=data)
+
+    # THEN we expect an idempotency key error message
+    assert "No data found to create a hashed idempotency_key" == e.value.args[0]
+
+
 def test_idempotent_data_sorting():
     # Scenario to validate same data in different order hashes to the same idempotency key
     data_one = {"data": "test message 1", "more_data": "more data 1"}