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https://issues.apache.org/jira/browse/BEAM-9377?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17068131#comment-17068131
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Udi Meiri commented on BEAM-9377:
---------------------------------
Verified for myself that Nones returned from map_fn indeed appear in the
PCollection:
{code}
def test_typed_map_optional(self):
# Optional does affect output type (Nones are NOT ignored).
def map_fn(element: int) -> typehints.Optional[int]:
if element == 1:
return None
else:
return element
result = [1, 2, 3] | beam.Map(map_fn)
self.assertCountEqual([None, 2, 3], result)
{code}
> 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
> Priority: Major
>
> 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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