[BEAM-8464] Python typehints: merge unions of tuples of the same size

• Type: Bug
• Status: Open
• Priority: P3
• Resolution: Unresolved
• Component/s: sdk-py-core
• Labels: types
• Assignee: Unassigned
• Reporter: Udi Meiri
• Created: 23/Oct/19 16:57
• Updated: 04/Jun/22 13:55

Description

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]])