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69d79f534e82fc32267e61a1a10e319ca51585bd
[etc/vim.git] / src / black / concurrency.py
1 import asyncio
2 import logging
3 import sys
4 from typing import Any, Iterable
5
6 from black.output import err
7
8
9 def maybe_install_uvloop() -> None:
10     """If our environment has uvloop installed we use it.
11
12     This is called only from command-line entry points to avoid
13     interfering with the parent process if Black is used as a library.
14
15     """
16     try:
17         import uvloop
18
19         uvloop.install()
20     except ImportError:
21         pass
22
23
24 def cancel(tasks: Iterable["asyncio.Task[Any]"]) -> None:
25     """asyncio signal handler that cancels all `tasks` and reports to stderr."""
26     err("Aborted!")
27     for task in tasks:
28         task.cancel()
29
30
31 def shutdown(loop: asyncio.AbstractEventLoop) -> None:
32     """Cancel all pending tasks on `loop`, wait for them, and close the loop."""
33     try:
34         if sys.version_info[:2] >= (3, 7):
35             all_tasks = asyncio.all_tasks
36         else:
37             all_tasks = asyncio.Task.all_tasks
38         # This part is borrowed from asyncio/runners.py in Python 3.7b2.
39         to_cancel = [task for task in all_tasks(loop) if not task.done()]
40         if not to_cancel:
41             return
42
43         for task in to_cancel:
44             task.cancel()
45         loop.run_until_complete(
46             asyncio.gather(*to_cancel, loop=loop, return_exceptions=True)
47         )
48     finally:
49         # `concurrent.futures.Future` objects cannot be cancelled once they
50         # are already running. There might be some when the `shutdown()` happened.
51         # Silence their logger's spew about the event loop being closed.
52         cf_logger = logging.getLogger("concurrent.futures")
53         cf_logger.setLevel(logging.CRITICAL)
54         loop.close()