kennknowles opened a new issue, #18957:
URL: https://github.com/apache/beam/issues/18957
TLDR: if you have a multi-output DoFn, then the non-main PCollections with
incorrectly have their element types set to None. This affects type checking
for pipelines involving these PCollections.
Minimal example:
```
import apache_beam as beam
class TripleDoFn(beam.DoFn):
def process(self, elem):
yield_elem
if elem % 2 == 0:
yield beam.pvalue.TaggedOutput('ten_times', elem * 10)
if elem % 3
== 0:
yield beam.pvalue.TaggedOutput('hundred_times', elem * 100)
@beam.typehints.with_input_types(int)
@beam.typehints.with_output_types(int)
class
MultiplyBy(beam.DoFn):
def __init__(self, multiplier):
self._multiplier = multiplier
def
process(self, elem):
return elem * self._multiplier
def main():
with beam.Pipeline() as
p:
x, a, b = (
p
| 'Create' >> beam.Create([1, 2, 3])
| 'TripleDo' >> beam.ParDo(TripleDoFn()).with_outputs(
'ten_times', 'hundred_times', main='main_output'))
_ = a | 'MultiplyBy2' >> beam.ParDo(MultiplyBy(2))
if
__name__ == '__main__':
main()
```
Running this yields the following error:
```
apache_beam.typehints.decorators.TypeCheckError: Type hint violation for
'MultiplyBy2': requires <type
'int'> but got None for elem
```
Replacing `a` with `b`Â yields the same error. Replacing `a` with `x` instead
yields the following error:
```
apache_beam.typehints.decorators.TypeCheckError: Type hint violation for
'MultiplyBy2': requires <type
'int'> but got Union[TaggedOutput, int] for elem
```
I would expect Beam to correctly infer that `a` and `b` have element types
of `int` rather than `None`, and I would also expect Beam to correctly figure
out that the element types of `x` are compatible with `int`.
Imported from Jira
[BEAM-4132](https://issues.apache.org/jira/browse/BEAM-4132). Original Jira may
contain additional context.
Reported by: chuanyu.
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