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https://issues.apache.org/jira/browse/BEAM-8381?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kenneth Knowles updated BEAM-8381:
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Status: Open (was: Triage Needed)
> 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
> 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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