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https://issues.apache.org/jira/browse/BEAM-13439?focusedWorklogId=721344&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-721344
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ASF GitHub Bot logged work on BEAM-13439:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 05/Feb/22 02:19
Start Date: 05/Feb/22 02:19
Worklog Time Spent: 10m
Work Description: aaltay commented on pull request #16517:
URL: https://github.com/apache/beam/pull/16517#issuecomment-1030501495
@tvalentyn - Would you be able to take a look at this change? Or find
another person to review?
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Issue Time Tracking
-------------------
Worklog Id: (was: 721344)
Time Spent: 50m (was: 40m)
> Correct type signature on ptransform_fn to better support typecheckers
> ----------------------------------------------------------------------
>
> Key: BEAM-13439
> URL: https://issues.apache.org/jira/browse/BEAM-13439
> Project: Beam
> Issue Type: Improvement
> Components: sdk-py-core
> Affects Versions: 2.34.0
> Reporter: Sandy Chapman
> Priority: P2
> Labels: transform, typecheck
> Time Spent: 50m
> Remaining Estimate: 0h
>
> Because the return type of the ptransform_fn is not specified, [certain
> typecheckers|https://github.com/microsoft/pyright/issues/2688#issuecomment-990238720]
> will assume the type signature of functions decorated with it remain
> unchanged. However, ptransform_fn specifically adjusts the type signature
> such that the function no longer takes a pcoll.
> This can be corrected by changing the the definition of ptransform_fn from:
> {code:python}
> def ptransform_fn(fn):
> {code}
> to:
> {code:python}
> def ptransform_fn(fn) -> Callable[..., _PTransformFnPTransform]: {code}
> This allows the typechecker to understand the return type of a function
> decorated with ptransform_fn will instead be a _PTransformFnPTransform type.
> Additionally, for Python 3.10,
> [ParamSpec|https://www.python.org/dev/peps/pep-0612/#parameter-specification-variables]
> could be used to preserve the signature of the internal function as well.
> {code:python}
> from typing import ParamSpec, TypeVar, Concatenate
> P = ParamSpec("P")
> T = TypeVar("T")
> R = TypeVar("R")
> def ptransform_fn(fn: Callable[Concatenate[PCollection[T], P], R]) ->
> Callable[[P], _PTransformFnPTransform]: ...{code}
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