Python 3.7 "TCP echo server using streams" sample code does not work with uvloop.

[dstruck]

• uvloop version: 0.12.0
• Python version: 3.7.1
• Platform: Linux
• Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: not tested

Running the following code (source: https://docs.python.org/3/library/asyncio-stream.html#tcp-echo-server-using-streams) with uvloop:

import asyncio
import uvloop
import sys

async def handle_echo(reader, writer):
  data = await reader.read(100)
  message = data.decode()
  addr = writer.get_extra_info('peername')

  print(f"Received {message!r} from {addr!r}")

  print(f"Send: {message!r}")
  writer.write(data)
  await writer.drain()

  print("Close the connection")
  writer.close()

async def main():
  server = await asyncio.start_server(handle_echo, '127.0.0.1', 8888)

  addr = server.sockets[0].getsockname()
  print(f'Serving on {addr}')

  async with server:
    await server.serve_forever()

uvloop.install()

print("python version:", sys.version)
print("uvloop version:", uvloop.__version__)

asyncio.run(main())

Produces the following error message:

python uvlopp_issue.py 
python version: 3.7.1 (default, Dec 14 2018, 19:28:38) 
[GCC 7.3.0]
uvloop version: 0.12.0
Serving on ('127.0.0.1', 8888)
Traceback (most recent call last):
  File "uvlopp_issue.py", line 36, in <module>
    asyncio.run(main())
  File "/home/test/miniconda3/lib/python3.7/asyncio/runners.py", line 43, in run
    return loop.run_until_complete(main)
  File "uvloop/loop.pyx", line 1451, in uvloop.loop.Loop.run_until_complete
  File "uvlopp_issue.py", line 27, in main
    async with server:
AttributeError: __aexit__

[1st1]

Thank you for reporting. This is basically a duplicate of #211.

[jlaine]

This was fixed by PR #224

[ahesford]

I don't believe PR #224 fixes this issue. This issue is caused because the stock asyncio.base_events.Server in Python 3.7 was made into an asynchronous context manager. The entry method is simple:

async def __aenter__(self):
    return self

while the exit method closes the server:

async def __aexit__(self, *exc):
    self.close()
    await self.wait_closed()

The TCP echo server uses this manager in an async with server clause to ensure the server closes.

The uvloop replacement, uvloop.loop.Server, does not implement the methods for an asynchronous context manager in the master branch or in commit #8fac545a9351935eefc0c8d281bebd0dd2917d66 to address PR #224.

[cemsbr]

The error persists. Won't the fix be merged?

Edit: more info:

• uvloop 0.12.2
• Python 3.7.3
• Platform: Linux

[jlaine]

The fix landed for v0.13.0, you can for instance give the release candidate a go: https://github.com/MagicStack/uvloop/releases/tag/v0.13.0rc1