TIL: Clean Up Tmux Service When Removed by Home Manager

Recently I stopped using tmux to try zellij, however I noticed when I removed tmux from my nix config. I was getting the following error, when rebuilding my home-manager config:

The user systemd session is degraded:
● tmux.service loaded failed failed tmux default session (detached)

Legend: LOAD   → Reflects whether the unit definition was properly loaded.
        ACTIVE → The high-level unit activation state, i.e. generalization of SUB.
        SUB    → The low-level unit activation state, values depend on unit type.

I was wondering where this error was coming from, turns it the symlink to tmux.service has not been deleted that nix would create.

ls -al ~/.config/systemd/user/tmux.service
Permissions Size User        Group       Date Modified Name
.rw-rw-r--   453 haseebmajid haseebmajid 22 Aug  2023   /home/haseebmajid/.config/systemd/user/tmux.service

If we look at other systemd services we can see them symlinked to a nix package in the nix store.

ls -al ~/.config/systemd/user
lrwxrwxrwx     - haseebmajid haseebmajid 20 Feb 17:04   spotifyd.service -> /nix/store/7v52bpcyi0zqv012rrmd7s2r742hb2cy-home-manager-files/.config/systemd/user/spotifyd.service
lrwxrwxrwx     - haseebmajid haseebmajid 20 Feb 17:04   swayidle.service -> /nix/store/7v52bpcyi0zqv012rrmd7s2r742hb2cy-home-manager-files/.config/systemd/user/swayidle.service

So we can simply remove the tmux file, rm ~/.config/systemd/user/tmux.service. I should look into why this symlink is not removed.