Udi Meiri created BEAM-9377:
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Summary: Python typehints: Map wrapper prevents Optional stripping
Key: BEAM-9377
URL: https://issues.apache.org/jira/browse/BEAM-9377
Project: Beam
Issue Type: New Feature
Components: sdk-py-core
Reporter: Udi Meiri
This existing test is wrong:
{code}
def test_map_wrapper_optional_output(self):
# Optional does affect output type (Nones are NOT ignored).
def map_fn(unused_element: int) -> typehints.Optional[int]:
return 1
th = beam.Map(map_fn).get_type_hints()
self.assertEqual(th.input_types, ((int, ), {}))
self.assertEqual(th.output_types, ((typehints.Optional[int], ), {}))
{code}
The resulting output type should be int.
{code}
inital output hint:
Optional[int]
with wrapper:
Iterable[Optional[int]]
with DoFn.default_type_hints:
Optional[int]
{code}
However any Nones returned by a DoFn's process method are dropped, so the
actual element_type returned is plain int.
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