2.54.2+21.10 introduces a call in vendor_conf.d/snapd.fish to fish function `fish_add_path` which requires fish 3.2 or later (Impish only packages fish 3.1)

This was fixed in https://bugs.launchpad.net/snapd/+bug/1957155 which so far is available only in snapd master.

as far as I can see `fish_add_path` is still called from data/env/snapd.fish on master (see https://github.com/snapcore/snapd/blob/master/data/env/snapd.fish.in#L3 for reference) and the mentioned bug and corresponding PR/fix only affect the setting of XDG_DATA_DIRS and not the invalid call to this non-existent function on fish <3.2

One more fix for fish https://github.com/snapcore/snapd/pull/11371 seems to work in Focal VM.

Still experiencing this on Ubuntu 21.10.

This bug seems to also be causing https://bugs.launchpad.net/ubuntu/+source/snapd/+bug/1960702

Got hit by this, flooded with cron emails, thanks.

For others affected who land here, I've found that the proper fix for the issue is:

```
apt purge snapd
apt-mark hold snapd
```

Good riddance.

Dear, Canonical, no one wants snapd, and it is pushing a large majority of your userbase away. Would love to keep using Ubuntu, but your decisions around snapd (such as discovering security updates aren't being applied at all to Firefox, thanks again for that) are making the Ubuntu ecosystem unusable, particularly for long time users.

The new snapd release 2.54.3+20.04.1ubuntu0.2 in focal makes this error message go away for me, but it completely broke my (Plasma) desktop session, because XDG_DATA_DIRS was not set before (making something fill it on start; don't know where that happens), but it now contains only /var/lib/snapd/desktop.
The session start adds some paths, but notably /usr/local/share and /usr/share are missing.

I fixed it for me by wrapping the last lines of /usr/share/fish/vendor_conf.d/snapd.fish in an if:

  12 │ if not set -q XDG_DATA_DIRS
  13 │ if not contains $snap_xdg_path $XDG_DATA_DIRS
  14 │ set XDG_DATA_DIRS $XDG_DATA_DIRS $snap_xdg_path
  15 │ end
  16 │ end

@ytvwld I have 2.54.3+20.04.1ubuntu0.2 version:

```
guest@ubuntu:~$ dpkg -l snapd
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-=======================-============-============================================
ii snapd 2.54.3+20.04.1ubuntu0.2 amd64 Daemon and tooling that enable snap packages
```

Which contains this bit in /usr/share/fish/vendor_conf.d/snapd.fish:

```
if not set -q XDG_DATA_DIRS
    set --global --export XDG_DATA_DIRS $XDG_DATA_DIRS
    # XDG_DATA_DIRS is not defined, set it to some reasonable defaults
    set XDG_DATA_DIRS (string join : /usr/local/share /usr/share)
end

if not contains $snap_xdg_path (string split : "$XDG_DATA_DIRS")
    set XDG_DATA_DIRS (string join : -- $XDG_DATA_DIRS $snap_xdg_path)
end
```

Which does not look like what you pasted. Can you double check you have the right version installed?

Oh, sorry. I had 2.54.3+20.04.1ubuntu0.1 installed, the newer one seems to mostly work.
I can log in and snap apps appear in the menu.
XDG_DATA_DIRS now contains /var/lib/snapd/desktop twice, but that does not seem to be a major problem.

Ok, I can confirm this is fixed now with version 2.54.3+20.04.1ubuntu0.2