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https://issues.apache.org/jira/browse/BEAM-8464?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16978590#comment-16978590
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Udi Meiri commented on BEAM-8464:
---------------------------------
We appear to have the check you're referring to
(https://github.com/apache/beam/blob/db11e06184cad5913cf45e694748f4665bf2f097/sdks/python/apache_beam/typehints/typehints.py#L1164-L1165)
but it didn't work in this case for some reason.
We are currently maintaining our own rules in typehints.py, until an
off-the-shelf library is available (I'm not aware of any, and pytypes doesn't
support Py3.7 yet).
> Python typehints: merge unions of tuples of the same size
> ---------------------------------------------------------
>
> Key: BEAM-8464
> URL: https://issues.apache.org/jira/browse/BEAM-8464
> Project: Beam
> Issue Type: Bug
> Components: sdk-py-core
> Reporter: Udi Meiri
> Priority: Minor
>
> When inferring PCollection element types, merge Unions of identically-sized
> Tuples:
> Union[Tuple[a, b], Tuple[c, d]] => Tuple[Union[a, c], Union[b, d]]
> cc: [~robertwb]
> Example:
> {code}
> def fn(element: Tuple[str, Any]):
> ....
> p | Create([('a', None), ('b', None)] + [('c', 1), ('d', 3)]) | ParDo(fn)
> {code}
> This pipeline will fail with something like:
> {code}
> apache_beam.typehints.decorators.TypeCheckError: Type hint violation for
> 'ParDo': requires Tuple[str, Any] but got Union[Tuple[str, NoneType],
> Tuple[str, int]] for element
> {code}
> In test form:
> {code}
> def test_union_of_tuple(self):
> self.assertCompatible(
> typehints.Tuple[str, typehints.Any],
> typehints.Union[typehints.Tuple[str, type(None)],
> typehints.Tuple[str, int]])
> {code}
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