Compatibility with asyncio TaskGroups

[crachefeu]

This might be linked to issue #7, but I am unsure.

In my use case I use aiocsv to write results to a single file from multiple result streams (from multiple databases). I noticed that I have many more lines in my result file than expected when I use create_task in asyncio.TaskGroup (python doc here, see example below). If I simply await the writer, I don't have the issue.

System specifications

I am running this on python 3.11.0, on MacOS 12.3.1, M1 chip with aiocsv 1.2.4.

Example Here is a simple example to illustrate the issue:

import asyncio
from aiocsv import AsyncWriter
import aiofiles

async def main(iterations):
    async with aiofiles.open('test.csv', 'w', encoding="utf-8") as f:
        writer =  AsyncWriter(f)
        async with asyncio.TaskGroup() as tg:
            for i in range(iterations):
                tg.create_task(writer.writerow([i, "ben","and jerry's"]))

if __name__ == "__main__":
    asyncio.run(main(10))

I would expect the snippet above to write 10 lines to a CSV file, instead I get 55.

Am I missing something obvious here? Thanks in advance for your help.

[MKuranowski]

You just create one big race by allowing 10 coroutines to use the same AsyncWriter concurrently. Synchronize access to the writer with an asyncio.Lock or something.