nox: [BUG] --no-reuse-existing-virtualenvs doesn't seem to work

Describe the bug

Adding --no-reuse-existing-virtualenvs does not seem to ignore the cache, and instead just reuses the existing environments anyway. Happened on the previous version, and then did a brew upgrade, and 2021.10.1 also has this problem. Unless I misunderstand this option, pretty sure it’s broken.

How to reproduce

@nox.session(reuse_venv=True)
def type(session):
    session.install('mypy')
    session.run('mypy')

(simplified slightly, should be unimportant)

$ nox --no-reuse-existing-virtualenvs -s type
nox > Running session type
nox > Re-using existing virtual environment at .nox/type.

Expected behavior The existing virtual environment should not have been reused. (It really was, not just visually; I was trying to remove an item from the install list, but it remained installed).

About this issue

Original URL
State: closed
Created 3 years ago
Reactions: 4
Comments: 18 (2 by maintainers)

Most upvoted comments

Alright, I think I understand what you’re getting at:

Without anything passed on the command-line, sessions marked True will be reused - this is the default behavior and matches the intended current behavior.
Command-line --reuse (True) reuses envs for all sessions except ones marked False. This matches the intended current behavior (that isn’t working correctly).
Command-line --reuse=always forces every session to re-use its env, and is not a valid option for local specification.
Command-line --reuse=never forces every session to re-create its env, and is not a valid option for local specification.

If that’s the case, that works for me.

theacodes on Oct 1, 2021

Hmm… Ideally we’d do the following (but it’s more work):

Use the command-line option if it’s set (either way).
Use the per-session setting from the noxfile, if it’s not None.
Use the global nox.options setting from the noxfile, if it’s not None.
Don’t reuse.

So this would split your True/False row in two cases, depending on where the global setting comes from.

Consider this noxfile:

import nox
nox.options.reuse_existing_virtualenvs = False
@nox.session(reuse_venvs=True):
def test(session):
    pass

I’d be surprised if the test session was not reused.

On the other hand, I’d expect nox --no-reuse-existing-virtualenvs --session test to disable reuse.

cjolowicz on Oct 1, 2021

This behavior is definitely ambiguous if we’re just using True/False. What do y’all think using “yes”, “no”, “always” and “never”?

So:

Command-line --reuse=yes reuses envs for all sessions except ones marked “never”.
Command-line --reuse=no (or unset) only reuses sessions marked “always”.
Command-line --reuse=always forces every session to re-use its env.
Command-line --reuse=never forces every session to re-create its env.

The noxfile.py option nox.options.reuse_existing_virtualenvs should behave the same as the other noxfile.py options - it provides a default for the command-line arg if it isn’t specified.

theacodes on Oct 1, 2021