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Allow to extend return types of functions decorated by ContextDecorator with None #14439

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Allow to extend return types of functions decorated by ContextDecorator with None #14439

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fff6ca5
Implement `_SuppressedExcReturnT`
bswck Jul 22, 2025
6db7d8d
Increase LoB and improve comments
bswck Jul 22, 2025
976351f
Remove `_F` and `_AF` type var
bswck Jul 22, 2025
9dd131f
Nit: remove commas where incorrect
bswck Jul 22, 2025
ed5debc
Improve the comments
bswck Jul 22, 2025
8eefca3
Delegate `_ExcReturnT` to `_GeneratorContextManager` optional type arg
bswck Jul 22, 2025
d604bb2
Add note on type argument inference
bswck Jul 22, 2025
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@bswck
bswck committed Jul 22, 2025
commit ed5debcd689485f99dc3eddab61d748535e799e3
19 changes: 9 additions & 10 deletions stdlib/contextlib.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -64,17 +64,16 @@ class AbstractAsyncContextManager(ABC, Protocol[_T_co, _ExitT_co]): # type: ign
self, exc_type: type[BaseException] | None, exc_value: BaseException | None, traceback: TracebackType | None, /
) -> _ExitT_co: ...

_SuppressedExcReturnT = TypeVar("_SuppressedExcReturnT", Never, None, default=Never)
_ExcReturnT = TypeVar("_ExcReturnT", Never, None, default=Never)

# __exit__ can suppress exceptions by returning a true value.
# _SuppressedReturnT extends the decorated function's return type with
# - Never (default, has no effect on the return type)
# if the decorating context manager never suppresses exceptions;
# - None if the decorating context manager may suppress exceptions.
# _ExcReturnT describes function's return type after an exception occurs:
# - Never (default, the context manager never suppresses exceptions)
# - None (the context manager may suppress exceptions)
# See #13512.
class ContextDecorator(Generic[_SuppressedExcReturnT]):
class ContextDecorator(Generic[_ExcReturnT]):
def _recreate_cm(self) -> Self: ...
def __call__(self, func: Callable[_P, _R]) -> Callable[_P, _R | _SuppressedExcReturnT]: ...
def __call__(self, func: Callable[_P, _R]) -> Callable[_P, _R | _ExcReturnT]: ...

class _GeneratorContextManagerBase(Generic[_G_co]):
# Ideally this would use ParamSpec, but that requires (*args, **kwargs), which this isn't. see #6676
Expand All @@ -96,10 +95,10 @@ class _GeneratorContextManager(
def contextmanager(func: Callable[_P, Iterator[_T_co]]) -> Callable[_P, _GeneratorContextManager[_T_co]]: ...

if sys.version_info >= (3, 10):
# _SuppressedReturnT: see ContextDecorator.
class AsyncContextDecorator(Generic[_SuppressedExcReturnT]):
# _ExcReturnT: see ContextDecorator.
class AsyncContextDecorator(Generic[_ExcReturnT]):
def _recreate_cm(self) -> Self: ...
def __call__(self, func: Callable[_P, _R]) -> Callable[_P, _R | _SuppressedExcReturnT]: ...
def __call__(self, func: Callable[_P, _R]) -> Callable[_P, _R | _ExcReturnT]: ...

class _AsyncGeneratorContextManager(
_GeneratorContextManagerBase[AsyncGenerator[_T_co, _SendT_contra]],
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