[BEAM-12457] beam crash when annotating function with typing.Protocol

• Type: Bug
• Status: Triage Needed
• Priority: P3
• Resolution: Unresolved
• Affects Version/s: 2.29.0, 2.31.0
• Component/s: sdk-py-core
• Assignee: Unassigned
• Reporter: Etienne POT
• Created: 07/Jun/21 12:52
• Updated: 04/Jun/22 20:50

Description

When annotating a function with a https://docs.python.org/3/library/typing.html#typing.Protocol:

class Data(typing.Protocol):
    def f(self) -> int:
        ...


def fn(x: Data) -> Data:
  ...

pipeline = (
   ...
   | beam.Map(fn)
   ...
)

Beam will crash when `pipeline_type_check=True` because isinstance(x, Data) raise an error.
Indeed, by default, Protocol are not runtime checkable.

```

  File "/usr/local/google/_blaze_epot/e52e0fa21f849d3c6badad5aaa8158a8/execroot/google3/blaze-out/k8-fastbuild/bin/third_party/py/tensorflow_datasets/scripts/tools/compute_split_info.runfiles/google3/third_party/py/apache_beam/transforms/ptransform.py", line 935, in type_check_inputs
    hint):
  File "/usr/local/google/_blaze_epot/e52e0fa21f849d3c6badad5aaa8158a8/execroot/google3/blaze-out/k8-fastbuild/bin/third_party/py/tensorflow_datasets/scripts/tools/compute_split_info.runfiles/google3/third_party/py/apache_beam/typehints/typehints.py", line 1172, in is_consistent_with
    return issubclass(sub, base)
  File "/usr/local/google/_blaze_epot/e52e0fa21f849d3c6badad5aaa8158a8/execroot/google3/blaze-out/k8-fastbuild/bin/third_party/py/tensorflow_datasets/scripts/tools/compute_split_info.runfiles/google3/third_party/py/typing_extensions/src_py3/typing_extensions.py", line 1265, in __subclasscheck__
    raise TypeError("Instance and class checks can only be used with"
TypeError: Instance and class checks can only be used with @runtime protocols

```

Even if protocol are not runtime checkable, this is a perfectly valid python annotation, so beam should not raise error. For example, beam could ignore the annotation if isinstance raise error