[jira] [Closed] (FLINK-39578) Missing py.typed in PyFlink wheel prevents type checking with mypy

["Dian Fu (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-39578?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dian Fu closed FLINK-39578.
---------------------------
    Fix Version/s: 2.4.0
       Resolution: Fixed

Merged to master via f3cfe3e869dcc96d72724b5a3223cd909b1136e8

> Missing py.typed in PyFlink wheel prevents type checking with mypy
> ------------------------------------------------------------------
>
>                 Key: FLINK-39578
>                 URL: https://issues.apache.org/jira/browse/FLINK-39578
>             Project: Flink
>          Issue Type: Bug
>          Components: API / Python
>            Reporter: Florian Vazelle
>            Assignee: Florian Vazelle
>            Priority: Minor
>              Labels: pull-request-available
>             Fix For: 2.4.0
>
>
> PyFlink currently does not include a {{py.typed}} marker file in its distributed wheel. As a result, static type checkers like {{mypy}} treat the package as untyped, even though type annotations are present in the source code.
> This prevents users from benefiting from type checking when using PyFlink, as {{mypy}} ignores inline type hints unless the package explicitly declares itself as typed per [PEP 561|https://peps.python.org/pep-0561/].
> *Steps to Reproduce:*
> {code:bash}
> $ uv init test
> $ cd test/
> $ uv add apache-flink
> $ uv add mypy --group dev{code}
> Edit the {{{}main.py{}}}: 
> {code:python}
> from pyflink.datastream.functions import FlatMapFunction
> class MyFlatMapFunction(FlatMapFunction):
>     pass{code}
> {code:bash}
> $ uv run mypy .
> main.py:1: error: Skipping analyzing "pyflink.datastream.functions": module is installed, but missing library stubs or py.typed marker  [import-untyped]
> main.py:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
> {code}
> *Expected Behavior:*
> PyFlink should be recognized as a typed package, allowing mypy to analyze its type annotations.
> *Suggested Fix:*
> Include an empty {{py.typed}} file in the pyflink package and ensure it is packaged in the wheel.



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