Currently, asyncio.wait_for(fut), upon reaching the timeout deadline,
cancels the future and returns immediately. This is problematic for
when *fut* is a Task, because it will be left running for an arbitrary
amount of time. This behavior is iself surprising and may lead to
related bugs such as the one described in bpo-33638:
condition = asyncio.Condition()
async with condition:
await asyncio.wait_for(condition.wait(), timeout=0.5)
Currently, instead of raising a TimeoutError, the above code will fail
with `RuntimeError: cannot wait on un-acquired lock`, because
`__aexit__` is reached _before_ `condition.wait()` finishes its
cancellation and re-acquires the condition lock.
To resolve this, make `wait_for` await for the task cancellation.
The tradeoff here is that the `timeout` promise may be broken if the
task decides to handle its cancellation in a slow way. This represents
a behavior change and should probably not be back-patched to 3.6 and
earlier.
(cherry picked from commit e2b340ab41)
Co-authored-by: Elvis Pranskevichus <elvis@magic.io>
Fix the following bugs in the C implementation:
* get_future_loop() silenced all exceptions raised when look up the get_loop
attribute, not just an AttributeError.
* enter_task() silenced all exceptions raised when look up the current task,
not just a KeyError.
* repr() was called for a borrowed link in enter_task() and task_step_impl().
* str() was used instead of repr() in formatting one error message (in
Python implementation too).
* There where few reference leaks in error cases.
(cherry picked from commit 6655354afc)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Specifically, it's not possible to subclass Task/Future classes
and override the following methods:
* Future._schedule_callbacks
* Task._step
* Task._wakeup
* Convert asyncio/tasks.py to async/await
* Convert asyncio/queues.py to async/await
* Convert asyncio/test_utils.py to async/await
* Convert asyncio/base_subprocess.py to async/await
* Convert asyncio/subprocess.py to async/await
* Convert asyncio/streams.py to async/await
* Fix comments
* Convert asyncio/locks.py to async/await
* Convert asyncio.sleep to async def
* Add a comment
* Add missing news
* Convert stubs from AbstrctEventLoop to async functions
* Convert subprocess_shell/subprocess_exec
* Convert connect_read_pipe/connect_write_pip to async/await syntax
* Convert create_datagram_endpoint
* Convert create_unix_server/create_unix_connection
* Get rid of old style coroutines in unix_events.py
* Convert selector_events.py to async/await
* Convert wait_closed and create_connection
* Drop redundant line
* Convert base_events.py
* Code cleanup
* Drop redundant comments
* Fix indentation
* Add explicit tests for compatibility between old and new coroutines
* Convert windows event loop to use async/await
* Fix double awaiting of async function
* Convert asyncio/locks.py
* Improve docstring
* Convert tests to async/await
* Convert more tests
* Convert more tests
* Convert more tests
* Convert tests
* Improve test
The asyncio/compat.py file was written to support Python < 3.5 and
Python < 3.5.2. But Python 3.5 doesn't accept bugfixes anymore, only
security fixes. There is no more need to backport bugfixes to Python
3.5, and so no need to have a single code base for Python 3.5, 3.6
and 3.7.
Say hello (again) to "async" and "await", who became real keywords in
Python 3.7 ;-)
when there are no more `await` or `yield (from)` before return in coroutine,
cancel was ignored.
example:
async def coro():
asyncio.Task.current_task().cancel()
return 42
...
res = await coro() # should raise CancelledError
This implementation provides additional 10-20% speed boost for
asyncio programs.
The patch also fixes _asynciomodule.c to use Arguments Clinic, and
makes '_schedule_callbacks' an overridable method (as it was in 3.5).
This is now an official "protected" API that can be used to write
classes that are duck-type-compatible with Future without subclassing
it. (For that purpose I also changed isinstance(result, Future) to
check for this attribute instead.)
Hopefully Amber Brown can use this to make Twisted.Deferred compatible
with asyncio.Future.
Tests and docs are TBD.
* Fix ResourceWarning warnings in test_streams
* Return True from StreamReader.eof_received() to fix
http://bugs.python.org/issue24539 (but still needs a unittest).
Add StreamReader.__repr__() for easy debugging.
* remove unused imports
* Issue #234: Drop JoinableQueue on Python 3.5+
Miss Islington (bot)
Yury Selivanov
Andrew Svetlov
Victor Stinner
Victor K
INADA Naoki
Charles Renwick
Mariatta Wijaya
Guido van Rossum
Yury Selivanov