pip config unset requires --user

[akaihola]

If you modify configuration using e.g.

pip config set global.use-feature 2020-resolver

it isn't possible to disable the resolver simply using

pip config unset global.use-feature

Instead, you'll need

pip config unset --user global.use-feature

I see this behavior on Fedora 30, Python 3.7 and pip 20.2.

After running pip config set global.use-feature 2020-resolver, the pip config debug command shows

env_var:
env:
global:
  /etc/xdg/pip/pip.conf, exists: False
  /etc/pip.conf, exists: False
site:
  /usr/pip.conf, exists: False
user:
  /home/akaihola/.pip/pip.conf, exists: False
  /home/akaihola/.config/pip/pip.conf, exists: True

Originally posted by @akaihola in #8661 (comment)

[pradyunsg]

❯ pip config set global.use-feature 2020-resolver
Writing to /Users/pradyunsg/.config/pip/pip.conf
❯ pip config unset global.use-feature
WARNING: --use-feature=2020-resolver no longer has any effect, since it is now the default dependency resolver in pip. This will become an error in pip 21.0.
Writing to /Users/pradyunsg/.config/pip/pip.conf

This now works as expected (current main, and I imagine the last release as well).