context class with dynamic descriptor

context.py

from __future__ import annotations

from contextvars import ContextVar
from typing import Callable, Generic, Type, TypeVar, Union

_CONTEXT: ContextVar[dict] = ContextVar("custom_context")
T = TypeVar("T")


class Descriptor(Generic[T]):
    def __init__(self, *, default: Union[T, Callable[[], T]]) -> None:
        self._default = default

    def __set_name__(self, owner: Type[object], name: str) -> None:
        """Magic setter that just works"""
        self._name = name

    def __get__(self, instance: object, owner: Type[object]) -> T:
        data = _CONTEXT.get({})
        if self._name in data:
            return data.get(self._name, self._default)

        if callable(self._default):
            # run once
            value = self._default()

            # set default and context to generated value
            self._default = value
            self.__set__(instance, value)

            return value

        return self._default

    def __set__(self, instance: object, value: T) -> None:
        data = _CONTEXT.get({})
        data[self._name] = value
        _CONTEXT.set(data)


class SomeClass:
    bool_one = Descriptor[bool](default=False)
    bool_two = Descriptor[bool](default=False)