124 lines
4 KiB
Python
124 lines
4 KiB
Python
"""
|
|
@asynccontextmanager code, copied from Python 3.7's contextlib.
|
|
For usage in Python 3.6.
|
|
"""
|
|
import abc
|
|
from functools import wraps
|
|
|
|
import _collections_abc
|
|
|
|
__all__ = ["asynccontextmanager"]
|
|
|
|
|
|
class AbstractAsyncContextManager(abc.ABC):
|
|
|
|
"""An abstract base class for asynchronous context managers."""
|
|
|
|
async def __aenter__(self):
|
|
"""Return `self` upon entering the runtime context."""
|
|
return self
|
|
|
|
@abc.abstractmethod
|
|
async def __aexit__(self, exc_type, exc_value, traceback):
|
|
"""Raise any exception triggered within the runtime context."""
|
|
return None
|
|
|
|
@classmethod
|
|
def __subclasshook__(cls, C):
|
|
if cls is AbstractAsyncContextManager:
|
|
return _collections_abc._check_methods(C, "__aenter__", "__aexit__")
|
|
return NotImplemented
|
|
|
|
|
|
class _GeneratorContextManagerBase:
|
|
"""Shared functionality for @contextmanager and @asynccontextmanager."""
|
|
|
|
def __init__(self, func, args, kwds):
|
|
self.gen = func(*args, **kwds)
|
|
self.func, self.args, self.kwds = func, args, kwds
|
|
# Issue 19330: ensure context manager instances have good docstrings
|
|
doc = getattr(func, "__doc__", None)
|
|
if doc is None:
|
|
doc = type(self).__doc__
|
|
self.__doc__ = doc
|
|
# Unfortunately, this still doesn't provide good help output when
|
|
# inspecting the created context manager instances, since pydoc
|
|
# currently bypasses the instance docstring and shows the docstring
|
|
# for the class instead.
|
|
# See http://bugs.python.org/issue19404 for more details.
|
|
|
|
|
|
class _AsyncGeneratorContextManager(
|
|
_GeneratorContextManagerBase, AbstractAsyncContextManager
|
|
):
|
|
"""Helper for @asynccontextmanager."""
|
|
|
|
async def __aenter__(self):
|
|
try:
|
|
return await self.gen.__anext__()
|
|
except StopAsyncIteration:
|
|
raise RuntimeError("generator didn't yield") from None
|
|
|
|
async def __aexit__(self, typ, value, traceback):
|
|
if typ is None:
|
|
try:
|
|
await self.gen.__anext__()
|
|
except StopAsyncIteration:
|
|
return
|
|
else:
|
|
raise RuntimeError("generator didn't stop")
|
|
else:
|
|
if value is None:
|
|
value = typ()
|
|
# See _GeneratorContextManager.__exit__ for comments on subtleties
|
|
# in this implementation
|
|
try:
|
|
await self.gen.athrow(typ, value, traceback)
|
|
raise RuntimeError("generator didn't stop after athrow()")
|
|
except StopAsyncIteration as exc:
|
|
return exc is not value
|
|
except RuntimeError as exc:
|
|
if exc is value:
|
|
return False
|
|
# Avoid suppressing if a StopIteration exception
|
|
# was passed to throw() and later wrapped into a RuntimeError
|
|
# (see PEP 479 for sync generators; async generators also
|
|
# have this behavior). But do this only if the exception wrapped
|
|
# by the RuntimeError is actully Stop(Async)Iteration (see
|
|
# issue29692).
|
|
if isinstance(value, (StopIteration, StopAsyncIteration)):
|
|
if exc.__cause__ is value:
|
|
return False
|
|
raise
|
|
except BaseException as exc:
|
|
if exc is not value:
|
|
raise
|
|
|
|
|
|
def asynccontextmanager(func):
|
|
"""@asynccontextmanager decorator.
|
|
Typical usage:
|
|
@asynccontextmanager
|
|
async def some_async_generator(<arguments>):
|
|
<setup>
|
|
try:
|
|
yield <value>
|
|
finally:
|
|
<cleanup>
|
|
This makes this:
|
|
async with some_async_generator(<arguments>) as <variable>:
|
|
<body>
|
|
equivalent to this:
|
|
<setup>
|
|
try:
|
|
<variable> = <value>
|
|
<body>
|
|
finally:
|
|
<cleanup>
|
|
"""
|
|
|
|
@wraps(func)
|
|
def helper(*args, **kwds):
|
|
return _AsyncGeneratorContextManager(func, args, kwds)
|
|
|
|
return helper
|