mirror of
https://github.com/python/cpython.git
synced 2024-11-24 17:47:13 +01:00
815 lines
27 KiB
Python
815 lines
27 KiB
Python
"""Utilities for with-statement contexts. See PEP 343."""
|
|
import abc
|
|
import os
|
|
import sys
|
|
import _collections_abc
|
|
from collections import deque
|
|
from functools import wraps
|
|
from types import MethodType, GenericAlias
|
|
|
|
__all__ = ["asynccontextmanager", "contextmanager", "closing", "nullcontext",
|
|
"AbstractContextManager", "AbstractAsyncContextManager",
|
|
"AsyncExitStack", "ContextDecorator", "ExitStack",
|
|
"redirect_stdout", "redirect_stderr", "suppress", "aclosing",
|
|
"chdir"]
|
|
|
|
|
|
class AbstractContextManager(abc.ABC):
|
|
|
|
"""An abstract base class for context managers."""
|
|
|
|
__class_getitem__ = classmethod(GenericAlias)
|
|
|
|
__slots__ = ()
|
|
|
|
def __enter__(self):
|
|
"""Return `self` upon entering the runtime context."""
|
|
return self
|
|
|
|
@abc.abstractmethod
|
|
def __exit__(self, exc_type, exc_value, traceback):
|
|
"""Raise any exception triggered within the runtime context."""
|
|
return None
|
|
|
|
@classmethod
|
|
def __subclasshook__(cls, C):
|
|
if cls is AbstractContextManager:
|
|
return _collections_abc._check_methods(C, "__enter__", "__exit__")
|
|
return NotImplemented
|
|
|
|
|
|
class AbstractAsyncContextManager(abc.ABC):
|
|
|
|
"""An abstract base class for asynchronous context managers."""
|
|
|
|
__class_getitem__ = classmethod(GenericAlias)
|
|
|
|
__slots__ = ()
|
|
|
|
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 ContextDecorator(object):
|
|
"A base class or mixin that enables context managers to work as decorators."
|
|
|
|
def _recreate_cm(self):
|
|
"""Return a recreated instance of self.
|
|
|
|
Allows an otherwise one-shot context manager like
|
|
_GeneratorContextManager to support use as
|
|
a decorator via implicit recreation.
|
|
|
|
This is a private interface just for _GeneratorContextManager.
|
|
See issue #11647 for details.
|
|
"""
|
|
return self
|
|
|
|
def __call__(self, func):
|
|
@wraps(func)
|
|
def inner(*args, **kwds):
|
|
with self._recreate_cm():
|
|
return func(*args, **kwds)
|
|
return inner
|
|
|
|
|
|
class AsyncContextDecorator(object):
|
|
"A base class or mixin that enables async context managers to work as decorators."
|
|
|
|
def _recreate_cm(self):
|
|
"""Return a recreated instance of self.
|
|
"""
|
|
return self
|
|
|
|
def __call__(self, func):
|
|
@wraps(func)
|
|
async def inner(*args, **kwds):
|
|
async with self._recreate_cm():
|
|
return await func(*args, **kwds)
|
|
return inner
|
|
|
|
|
|
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.
|
|
|
|
def _recreate_cm(self):
|
|
# _GCMB instances are one-shot context managers, so the
|
|
# CM must be recreated each time a decorated function is
|
|
# called
|
|
return self.__class__(self.func, self.args, self.kwds)
|
|
|
|
|
|
class _GeneratorContextManager(
|
|
_GeneratorContextManagerBase,
|
|
AbstractContextManager,
|
|
ContextDecorator,
|
|
):
|
|
"""Helper for @contextmanager decorator."""
|
|
|
|
def __enter__(self):
|
|
# do not keep args and kwds alive unnecessarily
|
|
# they are only needed for recreation, which is not possible anymore
|
|
del self.args, self.kwds, self.func
|
|
try:
|
|
return next(self.gen)
|
|
except StopIteration:
|
|
raise RuntimeError("generator didn't yield") from None
|
|
|
|
def __exit__(self, typ, value, traceback):
|
|
if typ is None:
|
|
try:
|
|
next(self.gen)
|
|
except StopIteration:
|
|
return False
|
|
else:
|
|
try:
|
|
raise RuntimeError("generator didn't stop")
|
|
finally:
|
|
self.gen.close()
|
|
else:
|
|
if value is None:
|
|
# Need to force instantiation so we can reliably
|
|
# tell if we get the same exception back
|
|
value = typ()
|
|
try:
|
|
self.gen.throw(value)
|
|
except StopIteration as exc:
|
|
# Suppress StopIteration *unless* it's the same exception that
|
|
# was passed to throw(). This prevents a StopIteration
|
|
# raised inside the "with" statement from being suppressed.
|
|
return exc is not value
|
|
except RuntimeError as exc:
|
|
# Don't re-raise the passed in exception. (issue27122)
|
|
if exc is value:
|
|
exc.__traceback__ = traceback
|
|
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 actually Stop(Async)Iteration (see
|
|
# issue29692).
|
|
if (
|
|
isinstance(value, StopIteration)
|
|
and exc.__cause__ is value
|
|
):
|
|
value.__traceback__ = traceback
|
|
return False
|
|
raise
|
|
except BaseException as exc:
|
|
# only re-raise if it's *not* the exception that was
|
|
# passed to throw(), because __exit__() must not raise
|
|
# an exception unless __exit__() itself failed. But throw()
|
|
# has to raise the exception to signal propagation, so this
|
|
# fixes the impedance mismatch between the throw() protocol
|
|
# and the __exit__() protocol.
|
|
if exc is not value:
|
|
raise
|
|
exc.__traceback__ = traceback
|
|
return False
|
|
try:
|
|
raise RuntimeError("generator didn't stop after throw()")
|
|
finally:
|
|
self.gen.close()
|
|
|
|
class _AsyncGeneratorContextManager(
|
|
_GeneratorContextManagerBase,
|
|
AbstractAsyncContextManager,
|
|
AsyncContextDecorator,
|
|
):
|
|
"""Helper for @asynccontextmanager decorator."""
|
|
|
|
async def __aenter__(self):
|
|
# do not keep args and kwds alive unnecessarily
|
|
# they are only needed for recreation, which is not possible anymore
|
|
del self.args, self.kwds, self.func
|
|
try:
|
|
return await anext(self.gen)
|
|
except StopAsyncIteration:
|
|
raise RuntimeError("generator didn't yield") from None
|
|
|
|
async def __aexit__(self, typ, value, traceback):
|
|
if typ is None:
|
|
try:
|
|
await anext(self.gen)
|
|
except StopAsyncIteration:
|
|
return False
|
|
else:
|
|
try:
|
|
raise RuntimeError("generator didn't stop")
|
|
finally:
|
|
await self.gen.aclose()
|
|
else:
|
|
if value is None:
|
|
# Need to force instantiation so we can reliably
|
|
# tell if we get the same exception back
|
|
value = typ()
|
|
try:
|
|
await self.gen.athrow(value)
|
|
except StopAsyncIteration as exc:
|
|
# Suppress StopIteration *unless* it's the same exception that
|
|
# was passed to throw(). This prevents a StopIteration
|
|
# raised inside the "with" statement from being suppressed.
|
|
return exc is not value
|
|
except RuntimeError as exc:
|
|
# Don't re-raise the passed in exception. (issue27122)
|
|
if exc is value:
|
|
exc.__traceback__ = traceback
|
|
return False
|
|
# Avoid suppressing if a Stop(Async)Iteration exception
|
|
# was passed to athrow() 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 actually Stop(Async)Iteration (see
|
|
# issue29692).
|
|
if (
|
|
isinstance(value, (StopIteration, StopAsyncIteration))
|
|
and exc.__cause__ is value
|
|
):
|
|
value.__traceback__ = traceback
|
|
return False
|
|
raise
|
|
except BaseException as exc:
|
|
# only re-raise if it's *not* the exception that was
|
|
# passed to throw(), because __exit__() must not raise
|
|
# an exception unless __exit__() itself failed. But throw()
|
|
# has to raise the exception to signal propagation, so this
|
|
# fixes the impedance mismatch between the throw() protocol
|
|
# and the __exit__() protocol.
|
|
if exc is not value:
|
|
raise
|
|
exc.__traceback__ = traceback
|
|
return False
|
|
try:
|
|
raise RuntimeError("generator didn't stop after athrow()")
|
|
finally:
|
|
await self.gen.aclose()
|
|
|
|
|
|
def contextmanager(func):
|
|
"""@contextmanager decorator.
|
|
|
|
Typical usage:
|
|
|
|
@contextmanager
|
|
def some_generator(<arguments>):
|
|
<setup>
|
|
try:
|
|
yield <value>
|
|
finally:
|
|
<cleanup>
|
|
|
|
This makes this:
|
|
|
|
with some_generator(<arguments>) as <variable>:
|
|
<body>
|
|
|
|
equivalent to this:
|
|
|
|
<setup>
|
|
try:
|
|
<variable> = <value>
|
|
<body>
|
|
finally:
|
|
<cleanup>
|
|
"""
|
|
@wraps(func)
|
|
def helper(*args, **kwds):
|
|
return _GeneratorContextManager(func, args, kwds)
|
|
return helper
|
|
|
|
|
|
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
|
|
|
|
|
|
class closing(AbstractContextManager):
|
|
"""Context to automatically close something at the end of a block.
|
|
|
|
Code like this:
|
|
|
|
with closing(<module>.open(<arguments>)) as f:
|
|
<block>
|
|
|
|
is equivalent to this:
|
|
|
|
f = <module>.open(<arguments>)
|
|
try:
|
|
<block>
|
|
finally:
|
|
f.close()
|
|
|
|
"""
|
|
def __init__(self, thing):
|
|
self.thing = thing
|
|
def __enter__(self):
|
|
return self.thing
|
|
def __exit__(self, *exc_info):
|
|
self.thing.close()
|
|
|
|
|
|
class aclosing(AbstractAsyncContextManager):
|
|
"""Async context manager for safely finalizing an asynchronously cleaned-up
|
|
resource such as an async generator, calling its ``aclose()`` method.
|
|
|
|
Code like this:
|
|
|
|
async with aclosing(<module>.fetch(<arguments>)) as agen:
|
|
<block>
|
|
|
|
is equivalent to this:
|
|
|
|
agen = <module>.fetch(<arguments>)
|
|
try:
|
|
<block>
|
|
finally:
|
|
await agen.aclose()
|
|
|
|
"""
|
|
def __init__(self, thing):
|
|
self.thing = thing
|
|
async def __aenter__(self):
|
|
return self.thing
|
|
async def __aexit__(self, *exc_info):
|
|
await self.thing.aclose()
|
|
|
|
|
|
class _RedirectStream(AbstractContextManager):
|
|
|
|
_stream = None
|
|
|
|
def __init__(self, new_target):
|
|
self._new_target = new_target
|
|
# We use a list of old targets to make this CM re-entrant
|
|
self._old_targets = []
|
|
|
|
def __enter__(self):
|
|
self._old_targets.append(getattr(sys, self._stream))
|
|
setattr(sys, self._stream, self._new_target)
|
|
return self._new_target
|
|
|
|
def __exit__(self, exctype, excinst, exctb):
|
|
setattr(sys, self._stream, self._old_targets.pop())
|
|
|
|
|
|
class redirect_stdout(_RedirectStream):
|
|
"""Context manager for temporarily redirecting stdout to another file.
|
|
|
|
# How to send help() to stderr
|
|
with redirect_stdout(sys.stderr):
|
|
help(dir)
|
|
|
|
# How to write help() to a file
|
|
with open('help.txt', 'w') as f:
|
|
with redirect_stdout(f):
|
|
help(pow)
|
|
"""
|
|
|
|
_stream = "stdout"
|
|
|
|
|
|
class redirect_stderr(_RedirectStream):
|
|
"""Context manager for temporarily redirecting stderr to another file."""
|
|
|
|
_stream = "stderr"
|
|
|
|
|
|
class suppress(AbstractContextManager):
|
|
"""Context manager to suppress specified exceptions
|
|
|
|
After the exception is suppressed, execution proceeds with the next
|
|
statement following the with statement.
|
|
|
|
with suppress(FileNotFoundError):
|
|
os.remove(somefile)
|
|
# Execution still resumes here if the file was already removed
|
|
"""
|
|
|
|
def __init__(self, *exceptions):
|
|
self._exceptions = exceptions
|
|
|
|
def __enter__(self):
|
|
pass
|
|
|
|
def __exit__(self, exctype, excinst, exctb):
|
|
# Unlike isinstance and issubclass, CPython exception handling
|
|
# currently only looks at the concrete type hierarchy (ignoring
|
|
# the instance and subclass checking hooks). While Guido considers
|
|
# that a bug rather than a feature, it's a fairly hard one to fix
|
|
# due to various internal implementation details. suppress provides
|
|
# the simpler issubclass based semantics, rather than trying to
|
|
# exactly reproduce the limitations of the CPython interpreter.
|
|
#
|
|
# See http://bugs.python.org/issue12029 for more details
|
|
if exctype is None:
|
|
return
|
|
if issubclass(exctype, self._exceptions):
|
|
return True
|
|
if issubclass(exctype, BaseExceptionGroup):
|
|
match, rest = excinst.split(self._exceptions)
|
|
if rest is None:
|
|
return True
|
|
raise rest
|
|
return False
|
|
|
|
|
|
class _BaseExitStack:
|
|
"""A base class for ExitStack and AsyncExitStack."""
|
|
|
|
@staticmethod
|
|
def _create_exit_wrapper(cm, cm_exit):
|
|
return MethodType(cm_exit, cm)
|
|
|
|
@staticmethod
|
|
def _create_cb_wrapper(callback, /, *args, **kwds):
|
|
def _exit_wrapper(exc_type, exc, tb):
|
|
callback(*args, **kwds)
|
|
return _exit_wrapper
|
|
|
|
def __init__(self):
|
|
self._exit_callbacks = deque()
|
|
|
|
def pop_all(self):
|
|
"""Preserve the context stack by transferring it to a new instance."""
|
|
new_stack = type(self)()
|
|
new_stack._exit_callbacks = self._exit_callbacks
|
|
self._exit_callbacks = deque()
|
|
return new_stack
|
|
|
|
def push(self, exit):
|
|
"""Registers a callback with the standard __exit__ method signature.
|
|
|
|
Can suppress exceptions the same way __exit__ method can.
|
|
Also accepts any object with an __exit__ method (registering a call
|
|
to the method instead of the object itself).
|
|
"""
|
|
# We use an unbound method rather than a bound method to follow
|
|
# the standard lookup behaviour for special methods.
|
|
_cb_type = type(exit)
|
|
|
|
try:
|
|
exit_method = _cb_type.__exit__
|
|
except AttributeError:
|
|
# Not a context manager, so assume it's a callable.
|
|
self._push_exit_callback(exit)
|
|
else:
|
|
self._push_cm_exit(exit, exit_method)
|
|
return exit # Allow use as a decorator.
|
|
|
|
def enter_context(self, cm):
|
|
"""Enters the supplied context manager.
|
|
|
|
If successful, also pushes its __exit__ method as a callback and
|
|
returns the result of the __enter__ method.
|
|
"""
|
|
# We look up the special methods on the type to match the with
|
|
# statement.
|
|
cls = type(cm)
|
|
try:
|
|
_enter = cls.__enter__
|
|
_exit = cls.__exit__
|
|
except AttributeError:
|
|
raise TypeError(f"'{cls.__module__}.{cls.__qualname__}' object does "
|
|
f"not support the context manager protocol") from None
|
|
result = _enter(cm)
|
|
self._push_cm_exit(cm, _exit)
|
|
return result
|
|
|
|
def callback(self, callback, /, *args, **kwds):
|
|
"""Registers an arbitrary callback and arguments.
|
|
|
|
Cannot suppress exceptions.
|
|
"""
|
|
_exit_wrapper = self._create_cb_wrapper(callback, *args, **kwds)
|
|
|
|
# We changed the signature, so using @wraps is not appropriate, but
|
|
# setting __wrapped__ may still help with introspection.
|
|
_exit_wrapper.__wrapped__ = callback
|
|
self._push_exit_callback(_exit_wrapper)
|
|
return callback # Allow use as a decorator
|
|
|
|
def _push_cm_exit(self, cm, cm_exit):
|
|
"""Helper to correctly register callbacks to __exit__ methods."""
|
|
_exit_wrapper = self._create_exit_wrapper(cm, cm_exit)
|
|
self._push_exit_callback(_exit_wrapper, True)
|
|
|
|
def _push_exit_callback(self, callback, is_sync=True):
|
|
self._exit_callbacks.append((is_sync, callback))
|
|
|
|
|
|
# Inspired by discussions on http://bugs.python.org/issue13585
|
|
class ExitStack(_BaseExitStack, AbstractContextManager):
|
|
"""Context manager for dynamic management of a stack of exit callbacks.
|
|
|
|
For example:
|
|
with ExitStack() as stack:
|
|
files = [stack.enter_context(open(fname)) for fname in filenames]
|
|
# All opened files will automatically be closed at the end of
|
|
# the with statement, even if attempts to open files later
|
|
# in the list raise an exception.
|
|
"""
|
|
|
|
def __enter__(self):
|
|
return self
|
|
|
|
def __exit__(self, *exc_details):
|
|
exc = exc_details[1]
|
|
received_exc = exc is not None
|
|
|
|
# We manipulate the exception state so it behaves as though
|
|
# we were actually nesting multiple with statements
|
|
frame_exc = sys.exception()
|
|
def _fix_exception_context(new_exc, old_exc):
|
|
# Context may not be correct, so find the end of the chain
|
|
while 1:
|
|
exc_context = new_exc.__context__
|
|
if exc_context is None or exc_context is old_exc:
|
|
# Context is already set correctly (see issue 20317)
|
|
return
|
|
if exc_context is frame_exc:
|
|
break
|
|
new_exc = exc_context
|
|
# Change the end of the chain to point to the exception
|
|
# we expect it to reference
|
|
new_exc.__context__ = old_exc
|
|
|
|
# Callbacks are invoked in LIFO order to match the behaviour of
|
|
# nested context managers
|
|
suppressed_exc = False
|
|
pending_raise = False
|
|
while self._exit_callbacks:
|
|
is_sync, cb = self._exit_callbacks.pop()
|
|
assert is_sync
|
|
try:
|
|
if exc is None:
|
|
exc_details = None, None, None
|
|
else:
|
|
exc_details = type(exc), exc, exc.__traceback__
|
|
if cb(*exc_details):
|
|
suppressed_exc = True
|
|
pending_raise = False
|
|
exc = None
|
|
except BaseException as new_exc:
|
|
# simulate the stack of exceptions by setting the context
|
|
_fix_exception_context(new_exc, exc)
|
|
pending_raise = True
|
|
exc = new_exc
|
|
|
|
if pending_raise:
|
|
try:
|
|
# bare "raise exc" replaces our carefully
|
|
# set-up context
|
|
fixed_ctx = exc.__context__
|
|
raise exc
|
|
except BaseException:
|
|
exc.__context__ = fixed_ctx
|
|
raise
|
|
return received_exc and suppressed_exc
|
|
|
|
def close(self):
|
|
"""Immediately unwind the context stack."""
|
|
self.__exit__(None, None, None)
|
|
|
|
|
|
# Inspired by discussions on https://bugs.python.org/issue29302
|
|
class AsyncExitStack(_BaseExitStack, AbstractAsyncContextManager):
|
|
"""Async context manager for dynamic management of a stack of exit
|
|
callbacks.
|
|
|
|
For example:
|
|
async with AsyncExitStack() as stack:
|
|
connections = [await stack.enter_async_context(get_connection())
|
|
for i in range(5)]
|
|
# All opened connections will automatically be released at the
|
|
# end of the async with statement, even if attempts to open a
|
|
# connection later in the list raise an exception.
|
|
"""
|
|
|
|
@staticmethod
|
|
def _create_async_exit_wrapper(cm, cm_exit):
|
|
return MethodType(cm_exit, cm)
|
|
|
|
@staticmethod
|
|
def _create_async_cb_wrapper(callback, /, *args, **kwds):
|
|
async def _exit_wrapper(exc_type, exc, tb):
|
|
await callback(*args, **kwds)
|
|
return _exit_wrapper
|
|
|
|
async def enter_async_context(self, cm):
|
|
"""Enters the supplied async context manager.
|
|
|
|
If successful, also pushes its __aexit__ method as a callback and
|
|
returns the result of the __aenter__ method.
|
|
"""
|
|
cls = type(cm)
|
|
try:
|
|
_enter = cls.__aenter__
|
|
_exit = cls.__aexit__
|
|
except AttributeError:
|
|
raise TypeError(f"'{cls.__module__}.{cls.__qualname__}' object does "
|
|
f"not support the asynchronous context manager protocol"
|
|
) from None
|
|
result = await _enter(cm)
|
|
self._push_async_cm_exit(cm, _exit)
|
|
return result
|
|
|
|
def push_async_exit(self, exit):
|
|
"""Registers a coroutine function with the standard __aexit__ method
|
|
signature.
|
|
|
|
Can suppress exceptions the same way __aexit__ method can.
|
|
Also accepts any object with an __aexit__ method (registering a call
|
|
to the method instead of the object itself).
|
|
"""
|
|
_cb_type = type(exit)
|
|
try:
|
|
exit_method = _cb_type.__aexit__
|
|
except AttributeError:
|
|
# Not an async context manager, so assume it's a coroutine function
|
|
self._push_exit_callback(exit, False)
|
|
else:
|
|
self._push_async_cm_exit(exit, exit_method)
|
|
return exit # Allow use as a decorator
|
|
|
|
def push_async_callback(self, callback, /, *args, **kwds):
|
|
"""Registers an arbitrary coroutine function and arguments.
|
|
|
|
Cannot suppress exceptions.
|
|
"""
|
|
_exit_wrapper = self._create_async_cb_wrapper(callback, *args, **kwds)
|
|
|
|
# We changed the signature, so using @wraps is not appropriate, but
|
|
# setting __wrapped__ may still help with introspection.
|
|
_exit_wrapper.__wrapped__ = callback
|
|
self._push_exit_callback(_exit_wrapper, False)
|
|
return callback # Allow use as a decorator
|
|
|
|
async def aclose(self):
|
|
"""Immediately unwind the context stack."""
|
|
await self.__aexit__(None, None, None)
|
|
|
|
def _push_async_cm_exit(self, cm, cm_exit):
|
|
"""Helper to correctly register coroutine function to __aexit__
|
|
method."""
|
|
_exit_wrapper = self._create_async_exit_wrapper(cm, cm_exit)
|
|
self._push_exit_callback(_exit_wrapper, False)
|
|
|
|
async def __aenter__(self):
|
|
return self
|
|
|
|
async def __aexit__(self, *exc_details):
|
|
exc = exc_details[1]
|
|
received_exc = exc is not None
|
|
|
|
# We manipulate the exception state so it behaves as though
|
|
# we were actually nesting multiple with statements
|
|
frame_exc = sys.exception()
|
|
def _fix_exception_context(new_exc, old_exc):
|
|
# Context may not be correct, so find the end of the chain
|
|
while 1:
|
|
exc_context = new_exc.__context__
|
|
if exc_context is None or exc_context is old_exc:
|
|
# Context is already set correctly (see issue 20317)
|
|
return
|
|
if exc_context is frame_exc:
|
|
break
|
|
new_exc = exc_context
|
|
# Change the end of the chain to point to the exception
|
|
# we expect it to reference
|
|
new_exc.__context__ = old_exc
|
|
|
|
# Callbacks are invoked in LIFO order to match the behaviour of
|
|
# nested context managers
|
|
suppressed_exc = False
|
|
pending_raise = False
|
|
while self._exit_callbacks:
|
|
is_sync, cb = self._exit_callbacks.pop()
|
|
try:
|
|
if exc is None:
|
|
exc_details = None, None, None
|
|
else:
|
|
exc_details = type(exc), exc, exc.__traceback__
|
|
if is_sync:
|
|
cb_suppress = cb(*exc_details)
|
|
else:
|
|
cb_suppress = await cb(*exc_details)
|
|
|
|
if cb_suppress:
|
|
suppressed_exc = True
|
|
pending_raise = False
|
|
exc = None
|
|
except BaseException as new_exc:
|
|
# simulate the stack of exceptions by setting the context
|
|
_fix_exception_context(new_exc, exc)
|
|
pending_raise = True
|
|
exc = new_exc
|
|
|
|
if pending_raise:
|
|
try:
|
|
# bare "raise exc" replaces our carefully
|
|
# set-up context
|
|
fixed_ctx = exc.__context__
|
|
raise exc
|
|
except BaseException:
|
|
exc.__context__ = fixed_ctx
|
|
raise
|
|
return received_exc and suppressed_exc
|
|
|
|
|
|
class nullcontext(AbstractContextManager, AbstractAsyncContextManager):
|
|
"""Context manager that does no additional processing.
|
|
|
|
Used as a stand-in for a normal context manager, when a particular
|
|
block of code is only sometimes used with a normal context manager:
|
|
|
|
cm = optional_cm if condition else nullcontext()
|
|
with cm:
|
|
# Perform operation, using optional_cm if condition is True
|
|
"""
|
|
|
|
def __init__(self, enter_result=None):
|
|
self.enter_result = enter_result
|
|
|
|
def __enter__(self):
|
|
return self.enter_result
|
|
|
|
def __exit__(self, *excinfo):
|
|
pass
|
|
|
|
async def __aenter__(self):
|
|
return self.enter_result
|
|
|
|
async def __aexit__(self, *excinfo):
|
|
pass
|
|
|
|
|
|
class chdir(AbstractContextManager):
|
|
"""Non thread-safe context manager to change the current working directory."""
|
|
|
|
def __init__(self, path):
|
|
self.path = path
|
|
self._old_cwd = []
|
|
|
|
def __enter__(self):
|
|
self._old_cwd.append(os.getcwd())
|
|
os.chdir(self.path)
|
|
|
|
def __exit__(self, *excinfo):
|
|
os.chdir(self._old_cwd.pop())
|