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import asyncio
import sys
from typing import Any
from typing import Callable
from typing import Coroutine
import greenlet
from .. import exc
# implementation based on snaury gist at
# https://gist.github.com/snaury/202bf4f22c41ca34e56297bae5f33fef
# Issue for context: https://github.com/python-greenlet/greenlet/issues/173
class _AsyncIoGreenlet(greenlet.greenlet):
def __init__(self, fn, driver):
greenlet.greenlet.__init__(self, fn, driver)
self.driver = driver
def await_only(awaitable: Coroutine) -> Any:
"""Awaits an async function in a sync method.
The sync method must be insice a :func:`greenlet_spawn` context.
:func:`await_` calls cannot be nested.
:param awaitable: The coroutine to call.
"""
# this is called in the context greenlet while running fn
current = greenlet.getcurrent()
if not isinstance(current, _AsyncIoGreenlet):
raise exc.InvalidRequestError(
"greenlet_spawn has not been called; can't call await_() here."
)
# returns the control to the driver greenlet passing it
# a coroutine to run. Once the awaitable is done, the driver greenlet
# switches back to this greenlet with the result of awaitable that is
# then returned to the caller (or raised as error)
return current.driver.switch(awaitable)
def await_fallback(awaitable: Coroutine) -> Any:
"""Awaits an async function in a sync method.
The sync method must be insice a :func:`greenlet_spawn` context.
:func:`await_` calls cannot be nested.
:param awaitable: The coroutine to call.
"""
# this is called in the context greenlet while running fn
current = greenlet.getcurrent()
if not isinstance(current, _AsyncIoGreenlet):
loop = asyncio.get_event_loop()
if loop.is_running():
raise exc.InvalidRequestError(
"greenlet_spawn has not been called and asyncio event "
"loop is already running; can't call await_() here."
)
return loop.run_until_complete(awaitable)
return current.driver.switch(awaitable)
async def greenlet_spawn(fn: Callable, *args, **kwargs) -> Any:
"""Runs a sync function ``fn`` in a new greenlet.
The sync function can then use :func:`await_` to wait for async
functions.
:param fn: The sync callable to call.
:param \\*args: Positional arguments to pass to the ``fn`` callable.
:param \\*\\*kwargs: Keyword arguments to pass to the ``fn`` callable.
"""
context = _AsyncIoGreenlet(fn, greenlet.getcurrent())
# runs the function synchronously in gl greenlet. If the execution
# is interrupted by await_, context is not dead and result is a
# coroutine to wait. If the context is dead the function has
# returned, and its result can be returned.
try:
result = context.switch(*args, **kwargs)
while not context.dead:
try:
# wait for a coroutine from await_ and then return its
# result back to it.
value = await result
except Exception:
# this allows an exception to be raised within
# the moderated greenlet so that it can continue
# its expected flow.
result = context.throw(*sys.exc_info())
else:
result = context.switch(value)
finally:
# clean up to avoid cycle resolution by gc
del context.driver
return result
class AsyncAdaptedLock:
def __init__(self):
self.mutex = asyncio.Lock()
def __enter__(self):
await_fallback(self.mutex.acquire())
return self
def __exit__(self, *arg, **kw):
self.mutex.release()
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