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"""
Dummy contextvars implementation, to make prompt_toolkit work on Python 3.6.
As long as there is only one application running at a time, we don't need the
real contextvars. So, stuff like the telnet-server and so on requires 3.7.
"""
from typing import TYPE_CHECKING, Any, Callable, Generic, Optional, TypeVar
if TYPE_CHECKING:
from typing_extensions import ParamSpec
def copy_context() -> "Context":
return Context()
if TYPE_CHECKING:
_P = ParamSpec("_P")
_T = TypeVar("_T")
class Context:
def run(
self, callable: "Callable[_P, _T]", *args: "_P.args", **kwargs: "_P.kwargs"
) -> _T:
return callable(*args, **kwargs)
def copy(self) -> "Context":
return self
class Token(Generic[_T]):
pass
class ContextVar(Generic[_T]):
def __init__(self, name: str, *, default: Optional[_T] = None) -> None:
self._name = name
self._value = default
@property
def name(self) -> str:
return self._name
def get(self, default: Optional[_T] = None) -> _T:
result = self._value or default
if result is None:
raise LookupError
return result
def set(self, value: _T) -> Token[_T]:
self._value = value
return Token()
def reset(self, token: Token[_T]) -> None:
pass
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