Problem modifying PATH variable in fish config

Question

I have the following configuration in ~/.config/fish/conf.d/python.fish:

# Initialise pyenv if found
echo "Running python config"
if status --is-interactive && test -d "$HOME/.pyenv"
    echo "Inside pyenv if"
    set -pxg PATH $HOME/.pyenv/bin $HOME/.pyenv/shims
    source ("$HOME/.pyenv/bin/pyenv" init - | psub)
    echo "End pyenv if"
end

# Poetry settings
if status --is-interactive && test -d "$HOME/.pyenv"
    set -xg POETRY_VIRTUALENVS_IN_PROJECT 1
    set -xg POETRY_VIRTUALENVS_CREATE 1
    set -pxg PATH $HOME/.poetry/bin
end
echo "End python config"

Every single echo command in the configuration is executed when I am creating a new shell, but the PATH variable is not modified. However, the POETRY_ variables show up as expected.

But things work as expected if I source the file in an existing shell with

source ~/.config/fish/conf.d/python.fish

What could possibly be wrong here?

Update: The problem only occurs inside of tmux, and not when I am starting terminals like Alacritty or Kitty. But all echo commands is still run inside tmux.

Answer 1

This was a Debian bug - they added configuration that reset $PATH, and it happened after the user's configuration snippets but before config.fish.

This appears to be fixed in Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1000199 . Now they merely add the default directories instead of replacing $PATH entirely.

Because config.fish is read after all the conf.d files, you can always use config.fish to override anything done in the snippets, like if your vendor breaks things.