[New-bugs-announce] [issue44070] Regression with relative paths in sys.path in python 3.8.10

[James Saryerwinnie]

New submission from James Saryerwinnie <js at jamesls.com>:

There was a change in behavior in Python 3.8.10 when using relative paths in sys.path.  It appears that the paths are now converted to absolute paths that are cached and can cause import errors in some cases.

Repro:

$ cat repro.sh
#!/bin/bash
python --version
mkdir -p /tmp/repro/{A,B}/testproject
echo "msg = 'from A'" > /tmp/repro/A/testproject/app.py
echo "msg = 'from B'" > /tmp/repro/B/testproject/app.py
python -c "
import sys, os, shutil
os.chdir('/tmp/repro/A')
sys.path.append('testproject')
import app
print(app)
print(app.msg)

os.chdir('/tmp/repro/B')
shutil.rmtree('/tmp/repro/A')
del sys.modules['app']
import app
print(app)
print(app.msg)
"
rm -rf /tmp/repro




On Python 3.8.9 I get:

$ ./repro.sh
Python 3.8.9
<module 'app' from 'testproject/app.py'>
from A
<module 'app' from 'testproject/app.py'>
from B

On Python 3.8.10 I get:

$ ./repro.sh
Python 3.8.10
<module 'app' from '/private/tmp/repro/A/testproject/app.py'>
from A
Traceback (most recent call last):
  File "<string>", line 12, in <module>
ModuleNotFoundError: No module named 'app'


I haven't confirmed this (I can't work out the frozen bootstrap stuff), but this might be caused by https://bugs.python.org/issue43105, whose patch does seem to be converting paths to absolute paths.

----------
components: Library (Lib)
messages: 393212
nosy: James.Saryerwinnie
priority: normal
severity: normal
status: open
title: Regression with relative paths in sys.path in python 3.8.10
type: behavior
versions: Python 3.10, Python 3.11, Python 3.8, Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue44070>
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