claudevdm commented on code in PR #41184:
URL: https://github.com/apache/beam/pull/41184#discussion_r4539487289
##########
sdks/python/apache_beam/typehints/decorators.py:
##########
@@ -175,6 +175,35 @@ def _annotation_namespaces(fn):
return getattr(target, '__globals__', {}), localns
+def _is_valid_type_hint(hint):
+ """Whether a resolved annotation only contains valid type hint components.
+
+ A string annotation can resolve to an object that is not a type, e.g. a
+ protobuf enum (an ``EnumTypeWrapper`` instance) used as
+ ``Mapping[str, 'schema_pb2.FeatureType']``. Beam's composite type hints
+ reject such parameters, so these annotations must not be resolved.
+ """
+ if hint is None or hint is Ellipsis:
+ return True
+ if isinstance(hint, (list, tuple)):
+ # Callable parameter lists, e.g. the [int] in Callable[[int], str].
+ return all(_is_valid_type_hint(h) for h in hint)
+ origin = get_origin(hint)
+ if origin is Literal:
+ # Literal arguments are values, not types.
+ return True
+ args = get_args(hint)
+ if origin is typing.Annotated:
+ args = args[:1] # The remaining arguments are metadata.
+ if args:
+ return all(_is_valid_type_hint(arg) for arg in args)
+ try:
Review Comment:
`validate_composite_type_param` rejects TypeVars, NewTypes and `type`
aliases, so any string annotation using one now falls back to `Any`:
```python
from __future__ import annotations
import typing
import apache_beam as beam
T = typing.TypeVar('T')
def first(xs: list[T]) -> T:
return xs[0]
p = beam.Pipeline()
print((p | beam.Create([[1]]) | beam.Map(first)).element_type)
# master: <class 'int'> this PR: Any
```
Could we validate the converted hint instead? The enum case still falls
back, since a non-type comes back from `convert_to_beam_type` unchanged. A test
like the repro above would be good to add too.
```suggestion
try:
validate_composite_type_param(
convert_to_beam_type(hint), 'Resolved type annotation')
except (TypeError, ValueError):
return False
```
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