With this version bump my spotifyd service failed with

[ERROR] Caught panic with message: called `Result::unwrap()` on an `Err` value: Error("EOF while parsing a value", line: 1, column: 0)

The fix was to clear out the /var/spotifyd/cache directory. I guess the old cache was not compatible with the new version. Is there any way we can ensure that the cache is cleared when upgrading versions?

EDIT: Or perhaps we should ask upstream to fix this problem?

The cache issue is not Nix-specific, so I would go for upstream.

Will do. If upstream fixes this issue then I would vote for skipping the 0.2.20 version, so as to not break the spotifyd service for people.

The dbus start issue seems to be caused by spotifyd not running with X11. Not sure how much of an issue that is as I don't use spotifyd.

Definitely an issue since one use case (for example, my use case) is running spotifyd as a headless Spotify Connect client.

The cache issue is not Nix-specific, so I would go for upstream.

Will do.

Spotifyd/spotifyd#433

After clearing the cache I cannot reproduce the cache problem (see Spotifyd/spotifyd#433 for more details). Upstream will not fix the problem unless it happens more often. I guess we will have to accept that this version bump might break the spotifyd service? I would still need to see the DBUS without X11 problem solved before approving this pull request, though.

As a quick fix, we could encode spotifyd version in the cache directory name? Instead of /var/cache/spotifyd, it would be /var/cache/spotifyd-0.2.20

That would indeed solve the problem. But there are the obvious disadvantages to clearing the cache: songs need to be recached and credentials need to be added again. If the problem I ran into is rare enough then perhaps such a quickfix is not worth it? I do not know what to prefer here.

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-in-distress/3604/12