Bug report

Looked for similar issues and could not find any.

Steps to reproduce bug:

1. activate venv
2. spawn child fish process (or start tmux session)
3. activate same venv

source activate.fishfishsource activate.fish

Should output:
functions: Function “_old_fish_prompt” does not exist

Cause

I think I've identified the reason for the bug:

1. The environment variables set inactivate.fish are exported to child processes (script usesset -gx to set the variables).
2. However, the function_old_fish_prompt is not exported to child processes.

So, when we run fish from another fish session (such as in tmux), the variables set inactivate.fish are present in the child process, but the functions are not.

Fix

I've written a fix for this, which is to test if the_old_fish_prompt function exists before attempting to delete it. I can make a PR with this fix.

Also, the implementation fromvirtualenv does not suffer from this bug. They check if the function exists before deleting it.

Your environment

Ubuntu 22.04 amd64
Python 3.10.4
Python and venv packages installed from apt