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Add type signatures to lru_cache using overloads (not ready to merge) #13033

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Add type signatures to lru_cache using overloads (not ready to merge) #13033

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Add type signatures to lru_cache
alwaysmpe Nov 17, 2024
03e550f
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Nov 18, 2024
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44 changes: 35 additions & 9 deletions stdlib/functools.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ import sys
import types
from _typeshed import SupportsAllComparisons, SupportsItems
from collections.abc import Callable, Hashable, Iterable, Sequence, Sized
from typing import Any, Generic, Literal, NamedTuple, TypedDict, TypeVar, final, overload
from typing import Any, Generic, Literal, NamedTuple, Protocol, TypedDict, TypeVar, final, overload
from typing_extensions import ParamSpec, Self, TypeAlias

if sys.version_info >= (3, 9):
Expand Down Expand Up @@ -30,6 +30,8 @@ if sys.version_info >= (3, 9):
_T = TypeVar("_T")
_T_co = TypeVar("_T_co", covariant=True)
_S = TypeVar("_S")
_R = TypeVar("_R")
_P = ParamSpec("_P")
_PWrapped = ParamSpec("_PWrapped")
_RWrapped = TypeVar("_RWrapped")
_PWrapper = ParamSpec("_PWrapper")
Expand All @@ -51,22 +53,46 @@ if sys.version_info >= (3, 9):
maxsize: int
typed: bool

class _Function(Protocol[_P, _R]): # type: ignore[misc] # pyright: ignore reportInvalidTypeVarUse
def __call__(self, *args: _P.args, **kwds: _P.kwargs) -> _R: ...

class _Method(Protocol[_T, _P, _R]): # type: ignore[misc] # pyright: ignore reportInvalidTypeVarUse
def __call__(_self, self: _T, *args: _P.args, **kwds: _P.kwargs) -> _R: ...

class _Classmethod(Protocol[_T, _P, _R]): # type: ignore[misc] # pyright: ignore reportInvalidTypeVarUse
def __call__(_self, cls: type[_T], *args: _P.args, **kwds: _P.kwargs) -> _R: ...
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@alwaysmpe alwaysmpe Nov 18, 2024 •
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I think combine these and use Concatenate instead, avoid needing to explicitly name a parameter, partially fix issue mentioned by @Daverball

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I think that's pretty much what the closest to working earlier approach did, yes. But it still had its edge cases where it didn't work unfortunately. Maybe things are a little bit more forgiving now.

If I'm not mistaken what you're doing in addition to earlier approaches is to always accept both signatures for methods/classmethods (i.e. the one where you have to explicitly provide self/cls and the one where you don't), so you give up some type safety on instance.method() vs. Cls.method() since it would not be able to detect that you're missing a required parameter.

That might be a reasonable trade-off for the overall better type safety, although I fear that language servers will not know what to do with these overloads, so instead of no parameter hints you may get confusing/difficult to read hints, which could be seen as a regression in ergonomics.


_CacheFn: TypeAlias = _lru_cache_wrapper[_Function[_P, _R]]
_CacheMethod: TypeAlias = _lru_cache_wrapper[_Method[_T, _P, _R]]
_CacheClassmethod: TypeAlias = _lru_cache_wrapper[_Classmethod[_T, _P, _R]]
_C = TypeVar("_C", bound=Callable[..., Any])

@final
class _lru_cache_wrapper(Generic[_T]):
__wrapped__: Callable[..., _T]
def __call__(self, *args: Hashable, **kwargs: Hashable) -> _T: ...
class _lru_cache_wrapper(Generic[_C]):
__wrapped__: _C

@overload
def __call__(_self: _CacheMethod[_T, _P, _R], *args: _P.args, **kwargs: _P.kwargs) -> _R: ...
@overload
def __call__(_self: _CacheMethod[_T, _P, _R], self: _T, *args: _P.args, **kwargs: _P.kwargs) -> _R: ...
@overload
def __call__(_self: _CacheClassmethod[_T, _P, _R], *args: _P.args, **kwargs: _P.kwargs) -> _R: ...
@overload
def __call__(_self: _CacheClassmethod[_T, _P, _R], cls: type[_T], *args: _P.args, **kwargs: _P.kwargs) -> _R: ...
@overload
def __call__(_self: _CacheFn[_P, _R], *args: _P.args, **kwargs: _P.kwargs) -> _R: ...
def cache_info(self) -> _CacheInfo: ...
def cache_clear(self) -> None: ...
if sys.version_info >= (3, 9):
def cache_parameters(self) -> _CacheParameters: ...

def __copy__(self) -> _lru_cache_wrapper[_T]: ...
def __deepcopy__(self, memo: Any, /) -> _lru_cache_wrapper[_T]: ...
def __copy__(self) -> Self: ...
def __deepcopy__(self, memo: Any, /) -> Self: ...

@overload
def lru_cache(maxsize: int | None = 128, typed: bool = False) -> Callable[[Callable[..., _T]], _lru_cache_wrapper[_T]]: ...
def lru_cache(maxsize: int | None = 128, typed: bool = False) -> Callable[[_C], _lru_cache_wrapper[_C]]: ...
@overload
def lru_cache(maxsize: Callable[..., _T], typed: bool = False) -> _lru_cache_wrapper[_T]: ...
def lru_cache(maxsize: _C, typed: bool = False) -> _lru_cache_wrapper[_C]: ...

if sys.version_info >= (3, 12):
WRAPPER_ASSIGNMENTS: tuple[
Expand Down Expand Up @@ -199,7 +225,7 @@ class cached_property(Generic[_T_co]):
def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...

if sys.version_info >= (3, 9):
def cache(user_function: Callable[..., _T], /) -> _lru_cache_wrapper[_T]: ...
def cache(user_function: _C, /) -> _lru_cache_wrapper[_C]: ...

def _make_key(
args: tuple[Hashable, ...],
Expand Down