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add the AsyncExitStack backport, to restore support for Python 3.5 and 3.6

This commit is contained in:
Jack O'Connor 2018-10-03 15:27:45 -04:00
parent f2ab34e5ff
commit 0e9194f8ce
2 changed files with 221 additions and 2 deletions
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218
peru/async_exit_stack.py Normal file
View File

@ -0,0 +1,218 @@
# This definition of AsyncExitStack is copied entirely from
# https://github.com/sorcio/async_exit_stack, in order to support Python 3.5
# and 3.6.
#
# flake8: noqa
from collections import deque
import sys
from types import MethodType
class AsyncExitStack:
"""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.
"""
### _BaseExitStack staticmethods
@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
### AsyncExitStack staticmethods
@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
### _BaseExitStack methods
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.
_cm_type = type(cm)
_exit = _cm_type.__exit__
result = _cm_type.__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))
### AsyncExitStack methods
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.
"""
_cm_type = type(cm)
_exit = _cm_type.__aexit__
result = await _cm_type.__aenter__(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):
received_exc = exc_details[0] is not None
# We manipulate the exception state so it behaves as though
# we were actually nesting multiple with statements
frame_exc = sys.exc_info()[1]
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 old_exc:
# Context is already set correctly (see issue 20317)
return
if exc_context is None or 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 is_sync:
cb_suppress = cb(*exc_details)
else:
cb_suppress = await cb(*exc_details)
if cb_suppress:
suppressed_exc = True
pending_raise = False
exc_details = (None, None, None)
except:
new_exc_details = sys.exc_info()
# simulate the stack of exceptions by setting the context
_fix_exception_context(new_exc_details[1], exc_details[1])
pending_raise = True
exc_details = new_exc_details
if pending_raise:
try:
# bare "raise exc_details[1]" replaces our carefully
# set-up context
fixed_ctx = exc_details[1].__context__
raise exc_details[1]
except BaseException:
exc_details[1].__context__ = fixed_ctx
raise
return received_exc and suppressed_exc

5
peru/plugin.py
View File

@ -7,6 +7,7 @@ import tempfile
import yaml
from .async_helpers import create_subprocess_with_handle
from .async_exit_stack import AsyncExitStack
from . import cache
from . import compat
from .compat import makedirs
@ -60,7 +61,7 @@ async def _plugin_job(plugin_context, module_type, module_fields, command, env,
display_handle):
# We take several locks and other context managers in here. Using an
# AsyncExitStack saves us from indentation hell.
async with contextlib.AsyncExitStack() as stack:
async with AsyncExitStack() as stack:
definition = _get_plugin_definition(module_type, module_fields,
command)
exe = _get_plugin_exe(definition, command)
@ -188,7 +189,7 @@ def _plugin_env(plugin_context, plugin_definition, module_fields, command,
def _noop_lock():
return contextlib.AsyncExitStack() # a no-op context manager
return AsyncExitStack() # a no-op context manager
def _plugin_cache_lock(plugin_context, definition, module_fields):