[jira] [Assigned] (BEAM-8381) Typehints on DoFn subclass are incorrectly set on superclass

["Udi Meiri (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BEAM-8381?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Udi Meiri reassigned BEAM-8381:
-------------------------------

    Assignee: Udi Meiri

> Typehints on DoFn subclass are incorrectly set on superclass
> ------------------------------------------------------------
>
>                 Key: BEAM-8381
>                 URL: https://issues.apache.org/jira/browse/BEAM-8381
>             Project: Beam
>          Issue Type: Bug
>          Components: sdk-py-core
>            Reporter: Yifan Mai
>            Assignee: Udi Meiri
>            Priority: Minor
>
> Suppose a parent DoFn with typehints is subclassed into a child DoFn with different typehints. The typehints will be incorrectly set on the parent DoFn class instead of the child DoFn class, causing type checking errors. This only happens if the parent already has typehints; if the parent has no typehints, then the typehints are correctly set on the child.
> Here's a example test case. I would expect this example to run successfully, but instead it fails with {{apache_beam.typehints.decorators.TypeCheckError: Type hint violation for 'AddOneAndStringify': requires <class 'int'> but got <class 'str'> for element}}.
> {code}
> def test_do_fn_pipeline_pipeline_type_check_satisfied_with_subclassing(self):
>   @with_input_types(int)
>   @with_output_types(int)
>   class AddOne(beam.DoFn):
>     def add_one(elements):
>       return element + 1
>     def process(self, element):
>       return [add_one(element)]
>   @with_input_types(int)
>   @with_output_types(str)
>   class AddOneAndStringify(AddOne):
>     def process(self, element):
>       return [str(add_one(element))]
>   d = (self.p
>        | 'T' >> beam.Create([1, 2, 3]).with_output_types(int)
>        | 'AddOne' >> beam.ParDo(AddOne())
>        | 'AddOneAndStringify' >> beam.ParDo(AddOneAndStringify()))
>   assert_that(d, equal_to(['3', '4', '5']))
>   self.p.run()
> {code}



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