Also check the existence of _fields in addition to__annotations__ for NamedTuple.

[yilei]

Why? This addresses an issue in Python 3.13 where typing.Tuple might gained an __annotations__ attribute and this will fail to match NamedTuple. (Part of #34869.)

I'm not sure if this (the extra __annotations__) is a bug in CPython or not, but regardless I think it's safer to check the existence of _fields.

from typing import Annotated, Protocol, Tuple, runtime_checkable
@runtime_checkable
class MyProtocol(Protocol):
    def method(self) -> None: ...

print(f"Before, {hasattr(Tuple, '__annotations__')=}")

# After the following check, typing.Tuple.__annotations__ now exists.
isinstance(Annotated[float, 1], MyProtocol)

print(f"After, {hasattr(Tuple, '__annotations__')=}")

Once above code is run, import apache_beam will fail in Python 3.13:

    from apache_beam import metrics
apache_beam/__init__.py:88: in <module>
    from apache_beam import io
apache_beam/io/__init__.py:21: in <module>
    from apache_beam.io.avroio import *
apache_beam/io/avroio.py:59: in <module>
    from apache_beam.io import filebasedsink
apache_beam/io/filebasedsink.py:29: in <module>
    from apache_beam.io import iobase
apache_beam/io/iobase.py:55: in <module>
    from apache_beam.transforms import Impulse
apache_beam/transforms/__init__.py:27: in <module>
    from apache_beam.transforms.stats import *
apache_beam/transforms/stats.py:377: in init apache_beam.transforms.stats
    ???
apache_beam/typehints/typehints.py:611: in __getitem__
    return schemas.union_schema_type(params)
apache_beam/typehints/schemas.py:659: in union_schema_type
    for field in zip(*[named_fields_from_element_type(t) for t in element_types]):
apache_beam/typehints/schemas.py:649: in named_fields_from_element_type
    return named_fields_from_schema(schema_from_element_type(element_type))
apache_beam/typehints/schemas.py:639: in schema_from_element_type
    return named_tuple_to_schema(element_type)
apache_beam/typehints/schemas.py:622: in named_tuple_to_schema
    return typing_to_runner_api(named_tuple, schema_registry).row_type.schema
apache_beam/typehints/schemas.py:201: in typing_to_runner_api
    schema_registry=schema_registry).typing_to_runner_api(type_)
apache_beam/typehints/schemas.py:304: in typing_to_runner_api
    row_type_constraint = row_type.RowTypeConstraint.from_user_type(type_)
apache_beam/typehints/row_type.py:109: in from_user_type
    for name in user_type._fields]
/root/.pyenv/versions/3.13.7/lib/python3.13/typing.py:1365: in __getattr__
    return getattr(self.__origin__, attr)
E   AttributeError: type object 'tuple' has no attribute '_fields'

Tested with Python 3.13.7.

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[gemini-code-assist]

Summary of Changes

Hello @yilei, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refines the mechanism for identifying NamedTuple types within Apache Beam's type hinting system. By switching the detection from relying on the __annotations__ attribute to the _fields attribute, the change resolves a potential compatibility issue with Python 3.13 where typing.Tuple could be mistakenly identified as a NamedTuple, leading to runtime errors. This ensures more accurate and stable type handling for NamedTuple instances across different Python versions.

Highlights

• Python 3.13 Compatibility Fix: Addresses a compatibility issue in Python 3.13 where typing.Tuple might unexpectedly gain an __annotations__ attribute, causing NamedTuple detection to fail in Apache Beam.
• Robust NamedTuple Detection: Changes the NamedTuple identification logic from checking for __annotations__ to checking for the more reliable _fields attribute, ensuring correct type recognition.
• Preventing AttributeError: This change prevents an AttributeError: type object 'tuple' has no attribute '_fields' that could occur when apache_beam imports in Python 3.13 after certain typing module interactions.

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[github-actions]

Checks are failing. Will not request review until checks are succeeding. If you'd like to override that behavior, comment assign set of reviewers

[yilei]

assign set of reviewers

[yilei]

assign set of reviewers

[yilei]

I checked the PreCommit error, and I don't think it's related to this PR? I also tried using a dummy comment change in the PR, some TestMilvusSearchEnrichment tests also failed in a similar way, so I'm concluding they are unrelated/flaky.

[github-actions]

Assigning reviewers:

R: @tvalentyn for label python.

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[github-actions]

Assigning reviewers:

R: @tvalentyn for label python.

Note: If you would like to opt out of this review, comment assign to next reviewer.

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[tvalentyn]

Thanks @yilei !

[tvalentyn]

Very nice to cross paths again with you!

[yilei]

@tvalentyn I'm glad too! And thank you for all things beam!