aiohttp client closes files after sending

[Rapptz]

Long story short

aiohttp seems to close files after the request is over, meaning a file object cannot be reused once a request is sent.

Expected behaviour

The file should not be closed and I can reuse my file objects following a seek call.

Actual behaviour

aiohttp closes the file instead.

Traceback (most recent call last):
  File "test.py", line 31, in <module>
    asyncio.get_event_loop().run_until_complete(run())
  File "...\Python36\lib\asyncio\base_events.py", line 466, in run_until_complete
    return future.result()
  File "test.py", line 27, in run
    b.seek(0)
ValueError: I/O operation on closed file.

Steps to reproduce

import asyncio
import io
import aiohttp

async def run():
    b = io.BytesIO(b'test')
    async with aiohttp.ClientSession() as sess:
        for _ in range(2):
            b.seek(0)
            async with sess.post('https://httpbin.org/post', data=b) as resp:
                print(await resp.text())

asyncio.get_event_loop().run_until_complete(run())

The equivalent requests code does not error:

b = io.BytesIO(b'test')
for _ in range(2):
    b.seek(0)
    r = requests.post('https://httpbin.org/post', data=b)
    print(r.text)

Your environment

aiohttp version: 3.5.4
Python version: 3.6.1
OS: Windows 8.1

[aio-libs-bot]

GitMate.io thinks the contributor most likely able to help you is @asvetlov.

Possibly related issues are #3296 (aiohttp client session. it doesn't close a connection after keepalive_timeout), #1907 (aiohttp 2.x closing client request data stream), #3628 (Session not closed in aiohttp.request after exception), #2849 (Getting Connection closed with aiohttp client), and #58 (aiohttp.HttpClient).

[Rapptz]

I searched github earlier and didn't see the duplicate discussion in #1907 sorry.

If this is truly by design (and it seems to be) patching the close method to do nothing and then putting it back will work fine, e.g.

async def run():
    b = io.BytesIO(b'test')
    original = b.close
    b.close = lambda: None
    try:
        async with aiohttp.ClientSession() as sess:
            for _ in range(2):
                b.seek(0)
                async with sess.post('https://httpbin.org/post', data=b) as resp:
                    print(await resp.text())
    finally:
        b.close = original

The reason I needed the file to stay open is because I wanted to retry requests if they failed.