[jira] [Updated] (BEAM-8487) Python typehints: support forward references

["Beam JIRA Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BEAM-8487?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Beam JIRA Bot updated BEAM-8487:
--------------------------------
    Labels: stale-P2  (was: )

> Python typehints: support forward references
> --------------------------------------------
>
>                 Key: BEAM-8487
>                 URL: https://issues.apache.org/jira/browse/BEAM-8487
>             Project: Beam
>          Issue Type: Bug
>          Components: sdk-py-core
>            Reporter: Udi Meiri
>            Priority: P2
>              Labels: stale-P2
>          Time Spent: 2h 10m
>  Remaining Estimate: 0h
>
> Typehints may be given as string literals: https://www.python.org/dev/peps/pep-0484/#forward-references
> These are currently not evaluated and result in errors.
> Example 1:
> {code}
>   def test_typed_callable_string_hints(self):
>     def do_fn(element: 'int') -> 'typehints.List[str]':
>       return [[str(element)] * 2]
>     result = [1, 2] | beam.ParDo(do_fn)
>     self.assertEqual([['1', '1'], ['2', '2']], sorted(result))
> {code}
> This results in:
> {code}
> >     return issubclass(sub, base)
> E     TypeError: issubclass() arg 2 must be a class or tuple of classes
> typehints.py:1168: TypeError
> {code}
> Example 2:
> {code}
>   def test_typed_dofn_string_hints(self):
>     class MyDoFn(beam.DoFn):
>       def process(self, element: 'int') -> 'typehints.List[str]':
>         return [[str(element)] * 2]
>     result = [1, 2] | beam.ParDo(MyDoFn())
>     self.assertEqual([['1', '1'], ['2', '2']], sorted(result))
> {code}
> This results in:
> {code}
> >     raise ValueError('%s is not iterable' % type_hint)
> E     ValueError: typehints.List[str] is not iterable
> typehints.py:1194: ValueError
> {code}
> where the non-iterable entity the error refers to is a string literal ("typehints.List[str]").



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