New submission from Shantanu <[email protected]>:
To quote the docs (https://docs.python.org/3/library/asyncio-dev.html):
```
By default asyncio runs in production mode. In order to ease the development
asyncio has a debug mode.
There are several ways to enable asyncio debug mode:
Setting the PYTHONASYNCIODEBUG environment variable to 1.
Using the -X dev Python command line option.
Passing debug=True to asyncio.run().
Calling loop.set_debug().
```
Unfortunately, this documentation is misleading (or wrong) when using
asyncio.run. For instance, from a naive read of the above, I'd expect debug
mode to be True for many of the following:
```
~/tmp λ cat test57.py
import asyncio
import time
async def foo():
loop = asyncio.get_event_loop()
time.sleep(2)
print(loop.get_debug())
print(asyncio.coroutines._DEBUG)
asyncio.run(foo())
~/tmp λ python3 --version
Python 3.7.3
# expected
~/tmp λ python3 test57.py
False
False
# surprising, would expect this to work
~/tmp λ python3 -X dev test57.py
True
False
# surprising, would expect this to work
~/tmp λ PYTHONASYNCIODEBUG=1 python3 test57.py
True
False
# expected
~/tmp λ vim test57.py
~/tmp λ cat test57.py
import asyncio
import time
async def foo():
loop = asyncio.get_event_loop()
time.sleep(2)
print(loop.get_debug())
print(asyncio.coroutines._DEBUG)
asyncio.run(foo(), debug=True)
~/tmp λ python3 test57.py
False
True
Executing <Task finished coro=<foo() done, defined at test57.py:4> result=None
created at
/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.7/lib/python3.7/asyncio/base_events.py:563>
took 2.003 seconds
~/tmp λ
```
This appears to be because asyncio.run sets debug mode here:
https://github.com/python/cpython/blob/4a97b1517a6b5ff22e2984b677a680b07ff0ce11/Lib/asyncio/runners.py#L42
We should either change asyncio.run to use the existing value of debug mode if
left unspecified, or we should update the documentation to explicitly call out
that the environment variable and command line flag will not work when using
asyncio.run
----------
components: asyncio
messages: 376268
nosy: asvetlov, hauntsaninja, yselivanov
priority: normal
severity: normal
status: open
title: asyncio.run interacts surprisingly with debug mode
_______________________________________
Python tracker <[email protected]>
<https://bugs.python.org/issue41696>
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