codekingpro/portable-devtools

1"""Various helper functions."""2 3from __future__ import annotations4 5import sys6from collections.abc import Callable, Mapping7from functools import cached_property8from typing import Any, Generic, Protocol, TypeVar, overload9 10__all__ = ("under_cached_property", "cached_property")11 12 13if sys.version_info >= (3, 11):14    from typing import Self15else:16    Self = Any17 18_T = TypeVar("_T")19# We use Mapping to make it possible to use TypedDict, but this isn't20# technically type safe as we need to assign into the dict.21_Cache = TypeVar("_Cache", bound=Mapping[str, Any])22 23 24class _CacheImpl(Protocol[_Cache]):25    _cache: _Cache26 27 28class under_cached_property(Generic[_T]):29    """Use as a class method decorator.30 31    It operates almost exactly like32    the Python `@property` decorator, but it puts the result of the33    method it decorates into the instance dict after the first call,34    effectively replacing the function it decorates with an instance35    variable.  It is, in Python parlance, a data descriptor.36    """37 38    def __init__(self, wrapped: Callable[[Any], _T]) -> None:39        self.wrapped = wrapped40        self.__doc__ = wrapped.__doc__41        self.name = wrapped.__name__42 43    @overload44    def __get__(self, inst: None, owner: type[object] | None = None) -> Self: ...45 46    @overload47    def __get__(48        self, inst: _CacheImpl[Any], owner: type[object] | None = None49    ) -> _T: ...50 51    def __get__(52        self, inst: _CacheImpl[Any] | None, owner: type[object] | None = None53    ) -> _T | Self:54        if inst is None:55            return self56        try:57            return inst._cache[self.name]  # type: ignore[no-any-return]58        except KeyError:59            val = self.wrapped(inst)60            inst._cache[self.name] = val61            return val62 63    def __set__(self, inst: _CacheImpl[Any], value: _T) -> None:64        raise AttributeError("cached property is read-only")65