Update 2025-04-13_16:26:56

venv/lib/python3.11/site-packages/anyio/lowlevel.py

@@ -0,0 +1,161 @@
+from __future__ import annotations
+
+import enum
+from dataclasses import dataclass
+from typing import Any, Generic, Literal, TypeVar, overload
+from weakref import WeakKeyDictionary
+
+from ._core._eventloop import get_async_backend
+
+T = TypeVar("T")
+D = TypeVar("D")
+
+
+async def checkpoint() -> None:
+    """
+    Check for cancellation and allow the scheduler to switch to another task.
+
+    Equivalent to (but more efficient than)::
+
+        await checkpoint_if_cancelled()
+        await cancel_shielded_checkpoint()
+
+
+    .. versionadded:: 3.0
+
+    """
+    await get_async_backend().checkpoint()
+
+
+async def checkpoint_if_cancelled() -> None:
+    """
+    Enter a checkpoint if the enclosing cancel scope has been cancelled.
+
+    This does not allow the scheduler to switch to a different task.
+
+    .. versionadded:: 3.0
+
+    """
+    await get_async_backend().checkpoint_if_cancelled()
+
+
+async def cancel_shielded_checkpoint() -> None:
+    """
+    Allow the scheduler to switch to another task but without checking for cancellation.
+
+    Equivalent to (but potentially more efficient than)::
+
+        with CancelScope(shield=True):
+            await checkpoint()
+
+
+    .. versionadded:: 3.0
+
+    """
+    await get_async_backend().cancel_shielded_checkpoint()
+
+
+def current_token() -> object:
+    """
+    Return a backend specific token object that can be used to get back to the event
+    loop.
+
+    """
+    return get_async_backend().current_token()
+
+
+_run_vars: WeakKeyDictionary[Any, dict[str, Any]] = WeakKeyDictionary()
+_token_wrappers: dict[Any, _TokenWrapper] = {}
+
+
+@dataclass(frozen=True)
+class _TokenWrapper:
+    __slots__ = "_token", "__weakref__"
+    _token: object
+
+
+class _NoValueSet(enum.Enum):
+    NO_VALUE_SET = enum.auto()
+
+
+class RunvarToken(Generic[T]):
+    __slots__ = "_var", "_value", "_redeemed"
+
+    def __init__(self, var: RunVar[T], value: T | Literal[_NoValueSet.NO_VALUE_SET]):
+        self._var = var
+        self._value: T | Literal[_NoValueSet.NO_VALUE_SET] = value
+        self._redeemed = False
+
+
+class RunVar(Generic[T]):
+    """
+    Like a :class:`~contextvars.ContextVar`, except scoped to the running event loop.
+    """
+
+    __slots__ = "_name", "_default"
+
+    NO_VALUE_SET: Literal[_NoValueSet.NO_VALUE_SET] = _NoValueSet.NO_VALUE_SET
+
+    _token_wrappers: set[_TokenWrapper] = set()
+
+    def __init__(
+        self, name: str, default: T | Literal[_NoValueSet.NO_VALUE_SET] = NO_VALUE_SET
+    ):
+        self._name = name
+        self._default = default
+
+    @property
+    def _current_vars(self) -> dict[str, T]:
+        token = current_token()
+        try:
+            return _run_vars[token]
+        except KeyError:
+            run_vars = _run_vars[token] = {}
+            return run_vars
+
+    @overload
+    def get(self, default: D) -> T | D: ...
+
+    @overload
+    def get(self) -> T: ...
+
+    def get(
+        self, default: D | Literal[_NoValueSet.NO_VALUE_SET] = NO_VALUE_SET
+    ) -> T | D:
+        try:
+            return self._current_vars[self._name]
+        except KeyError:
+            if default is not RunVar.NO_VALUE_SET:
+                return default
+            elif self._default is not RunVar.NO_VALUE_SET:
+                return self._default
+
+        raise LookupError(
+            f'Run variable "{self._name}" has no value and no default set'
+        )
+
+    def set(self, value: T) -> RunvarToken[T]:
+        current_vars = self._current_vars
+        token = RunvarToken(self, current_vars.get(self._name, RunVar.NO_VALUE_SET))
+        current_vars[self._name] = value
+        return token
+
+    def reset(self, token: RunvarToken[T]) -> None:
+        if token._var is not self:
+            raise ValueError("This token does not belong to this RunVar")
+
+        if token._redeemed:
+            raise ValueError("This token has already been used")
+
+        if token._value is _NoValueSet.NO_VALUE_SET:
+            try:
+                del self._current_vars[self._name]
+            except KeyError:
+                pass
+        else:
+            self._current_vars[self._name] = token._value
+
+        token._redeemed = True
+
+    def __repr__(self) -> str:
+        return f"<RunVar name={self._name!r}>"