Re: [bug-report] potential bug of emms-playlist-mode on Emacs 27.1

[Yoni Rabkin]

John Wong <thjwong@gmail.com> writes:

> Hi EMMS Team,
>
> I have been enjoying emms with emacs - the best way to enjoy music and
> podcasts while doing my stuff in emacs.
>
> Yesterday after I upgraded my system to Devuan Chimaera (a systemd
> free, SysVinit version of Debian Bulleye) and hence the distributed
> Emacs to 27.1, the emms-playlist-mode doesn't work like before:
> 1. I can still connect to mpd using emms-player-mpd-connect
> 2. I can get to the mpd playlist using emms-playlist-mode-go
> 3. I can even play music using emms-player-mpd-play
>
> But whenever I interact with mpd using the emms-playlist-mode
> functions, or interact with mpd using the emacs *EMMS Playlist* buffer
> (e.g. press enter to play the song at the current line), the following
> happens:
> 1. an error message appears at the mini-buffer as follow:-
> error in process filter: Spurious communication from process mpd, see
> buffer *spurious*
> 2. the "playing", i.e. no playing but error message and proceeding to
> the next song on the playlist, keeps on going until the end of the
> playlist. And then another message in mini-buffer appears:-
> No next track in playlist
> 3. The *spurious* buffer has just the following followed by a newline
> OK MPD 0.22.4
>
> I am not sure if it is me or if it is some incompatibility issues with
> Emacs 27.1. Here are the details of my settings:
> MPD version 0.22.6
> GNU Emacs 27.1 "(build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.24,
> cairo version 1.16.0) of 2021-03-28, modified by Debian"
> EMMS 20211211.232 from MELPA


I just checked with a remote mpd instance I have here: mpd 0.21.20 and
Emacs 28.0.90, and all is well (my local instance of mpd is an ancient
0.19.12).

If someone happens to have an mpd 22.4 they can run against, please test
this.

Since mpd+emms worked fine back in the days when Emacs 27.1 was around,
I doubt that is the source of the issue. You could test this by
compiling Emacs 28.0.90 or similar and trying. Perhaps mpd changed
something between 0.21.20 and 0.22.4. I'll have to compile a more recent
version of mpd to check.

`emms-player-mpd-play' is called at the end of `emms-player-mpd-start',
and `emms-player-mpd-start' is what is called when you RET over a
track. So it may be a change in 22.4 in regards to something in that
function. However, without being able to recreate the bug I can't find
out what.

I'll report back once I've compiled the right versions of mpd and emacs
(unless someone has access to those and will beat me to it of course.)


-- 
   "Cut your own wood and it will warm you twice"