[GitHub] [beam] damccorm opened a new issue, #19903: Python typehints: merge unions of tuples of the same size

[GitBox <gi...@apache.org>]

damccorm opened a new issue, #19903:
URL: https://github.com/apache/beam/issues/19903

   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:
   ```
   
   def fn(element: Tuple[str, Any]):
     ....
   p | Create([('a', None), ('b', None)] + [('c', 1), ('d',
   3)]) | ParDo(fn)
   
   ```
   
   This pipeline will fail with something like:
   ```
   
   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
   
   ```
   
   
   In test form:
   ```
   
     def test_union_of_tuple(self):
       self.assertCompatible(
           typehints.Tuple[str, typehints.Any],
   
          typehints.Union[typehints.Tuple[str, type(None)],
                           typehints.Tuple[str,
   int]])
   
   ```
   
   
   Imported from Jira [BEAM-8464](https://issues.apache.org/jira/browse/BEAM-8464). Original Jira may contain additional context.
   Reported by: udim.


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