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e062359 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 | from __future__ import annotations
from abc import abstractmethod
from contextlib import AbstractAsyncContextManager, AbstractContextManager
from inspect import isasyncgen, iscoroutine, isgenerator
from types import TracebackType
from typing import Protocol, TypeVar, cast, final
_T_co = TypeVar("_T_co", covariant=True)
_ExitT_co = TypeVar("_ExitT_co", covariant=True, bound="bool | None")
class _SupportsCtxMgr(Protocol[_T_co, _ExitT_co]):
def __contextmanager__(self) -> AbstractContextManager[_T_co, _ExitT_co]: ...
class _SupportsAsyncCtxMgr(Protocol[_T_co, _ExitT_co]):
def __asynccontextmanager__(
self,
) -> AbstractAsyncContextManager[_T_co, _ExitT_co]: ...
class ContextManagerMixin:
"""
Mixin class providing context manager functionality via a generator-based
implementation.
This class allows you to implement a context manager via :meth:`__contextmanager__`
which should return a generator. The mechanics are meant to mirror those of
:func:`@contextmanager <contextlib.contextmanager>`.
.. note:: Classes using this mix-in are not reentrant as context managers, meaning
that once you enter it, you can't re-enter before first exiting it.
.. seealso:: :doc:`contextmanagers`
"""
__cm: AbstractContextManager[object, bool | None] | None = None
@final
def __enter__(self: _SupportsCtxMgr[_T_co, bool | None]) -> _T_co:
# Needed for mypy to assume self still has the __cm member
assert isinstance(self, ContextManagerMixin)
if self.__cm is not None:
raise RuntimeError(
f"this {self.__class__.__qualname__} has already been entered"
)
cm = self.__contextmanager__()
if not isinstance(cm, AbstractContextManager):
if isgenerator(cm):
raise TypeError(
"__contextmanager__() returned a generator object instead of "
"a context manager. Did you forget to add the @contextmanager "
"decorator?"
)
raise TypeError(
f"__contextmanager__() did not return a context manager object, "
f"but {cm.__class__!r}"
)
if cm is self:
raise TypeError(
f"{self.__class__.__qualname__}.__contextmanager__() returned "
f"self. Did you forget to add the @contextmanager decorator and a "
f"'yield' statement?"
)
value = cm.__enter__()
self.__cm = cm
return value
@final
def __exit__(
self: _SupportsCtxMgr[object, _ExitT_co],
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> _ExitT_co:
# Needed for mypy to assume self still has the __cm member
assert isinstance(self, ContextManagerMixin)
if self.__cm is None:
raise RuntimeError(
f"this {self.__class__.__qualname__} has not been entered yet"
)
# Prevent circular references
cm = self.__cm
del self.__cm
return cast(_ExitT_co, cm.__exit__(exc_type, exc_val, exc_tb))
@abstractmethod
def __contextmanager__(self) -> AbstractContextManager[object, bool | None]:
"""
Implement your context manager logic here.
This method **must** be decorated with
:func:`@contextmanager <contextlib.contextmanager>`.
.. note:: Remember that the ``yield`` will raise any exception raised in the
enclosed context block, so use a ``finally:`` block to clean up resources!
:return: a context manager object
"""
class AsyncContextManagerMixin:
"""
Mixin class providing async context manager functionality via a generator-based
implementation.
This class allows you to implement a context manager via
:meth:`__asynccontextmanager__`. The mechanics are meant to mirror those of
:func:`@asynccontextmanager <contextlib.asynccontextmanager>`.
.. note:: Classes using this mix-in are not reentrant as context managers, meaning
that once you enter it, you can't re-enter before first exiting it.
.. seealso:: :doc:`contextmanagers`
"""
__cm: AbstractAsyncContextManager[object, bool | None] | None = None
@final
async def __aenter__(self: _SupportsAsyncCtxMgr[_T_co, bool | None]) -> _T_co:
# Needed for mypy to assume self still has the __cm member
assert isinstance(self, AsyncContextManagerMixin)
if self.__cm is not None:
raise RuntimeError(
f"this {self.__class__.__qualname__} has already been entered"
)
cm = self.__asynccontextmanager__()
if not isinstance(cm, AbstractAsyncContextManager):
if isasyncgen(cm):
raise TypeError(
"__asynccontextmanager__() returned an async generator instead of "
"an async context manager. Did you forget to add the "
"@asynccontextmanager decorator?"
)
elif iscoroutine(cm):
cm.close()
raise TypeError(
"__asynccontextmanager__() returned a coroutine object instead of "
"an async context manager. Did you forget to add the "
"@asynccontextmanager decorator and a 'yield' statement?"
)
raise TypeError(
f"__asynccontextmanager__() did not return an async context manager, "
f"but {cm.__class__!r}"
)
if cm is self:
raise TypeError(
f"{self.__class__.__qualname__}.__asynccontextmanager__() returned "
f"self. Did you forget to add the @asynccontextmanager decorator and a "
f"'yield' statement?"
)
value = await cm.__aenter__()
self.__cm = cm
return value
@final
async def __aexit__(
self: _SupportsAsyncCtxMgr[object, _ExitT_co],
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> _ExitT_co:
assert isinstance(self, AsyncContextManagerMixin)
if self.__cm is None:
raise RuntimeError(
f"this {self.__class__.__qualname__} has not been entered yet"
)
# Prevent circular references
cm = self.__cm
del self.__cm
return cast(_ExitT_co, await cm.__aexit__(exc_type, exc_val, exc_tb))
@abstractmethod
def __asynccontextmanager__(
self,
) -> AbstractAsyncContextManager[object, bool | None]:
"""
Implement your async context manager logic here.
This method **must** be decorated with
:func:`@asynccontextmanager <contextlib.asynccontextmanager>`.
.. note:: Remember that the ``yield`` will raise any exception raised in the
enclosed context block, so use a ``finally:`` block to clean up resources!
:return: an async context manager object
"""
|