raams95 opened a new pull request, #40757:
URL: https://github.com/apache/beam/pull/40757
Fixes #20986
A type hint with a `typing.Protocol` that is not `@runtime_checkable` makes
the pipeline fail at construction:
```python
class HasUpper(typing.Protocol):
def upper(self) -> str:
...
def fn(element: HasUpper) -> str:
return element.upper()
with beam.Pipeline() as p:
_ = p | beam.Create(['a', 'b']) | beam.Map(fn)
```
```
TypeError: Instance and class checks can only be used with
@runtime_checkable protocols
```
`is_consistent_with(str, HasUpper)` calls `issubclass`, through beartype's
`is_subhint` or directly, and Python raises this error for such a Protocol.
With `--runtime_type_check` or `--performance_runtime_type_check`,
`check_constraint` calls `isinstance` on each element and fails the same way.
So a non-runtime Protocol hint works today only when the input type is exactly
the same Protocol.
A Protocol is matched structurally, and Beam cannot check that with
`issubclass` or `isinstance`. With this change, `is_consistent_with` returns
`True` when the base is such a Protocol, and `check_constraint` skips it, as it
does for `Any`. For these Protocols, both calls always raised the `TypeError`
before. The only caller that caught it is the runtime check of a `Union`, which
counted it as a mismatch, so a runtime check of `Optional[HasUpper]` now also
passes for a `str`. The element type stays the Protocol, so the coder does not
change. `@runtime_checkable` Protocols keep the `issubclass`/`isinstance`
checks that they have today.
Tests:
- `test_typed_map_protocol_input` in `typed_pipeline_test.py` runs the
pipeline above.
- `test_protocol_type_hint` in `typecheck_test.py` runs it with
`runtime_type_check=True`.
Both fail before the change and pass after it on Python 3.11, 3.12, 3.13 and
3.14.
Testing:
- `pytest apache_beam/typehints/typed_pipeline_test.py
apache_beam/typehints/typecheck_test.py -k protocol` on Python 3.11, 3.12, 3.13
and 3.14
- `pytest apache_beam/typehints apache_beam/transforms apache_beam/coders
apache_beam/pipeline_test.py` on Python 3.12
- `yapf --diff` and `ruff check` on the changed files
------------------------
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