gnu: mpd-service-type: Remove `group' from configuration.

Use of the `group' option in the MPD configuration behaves oddly: when it’s
present, the MPD process runs without the supplementary groups the user is in.
Leaving it unspecified does the right thing, the process gets both the primary
and supplementary groups.  So, don’t serialize that option at all.

* gnu/services/audio.scm (%mpd-user): Use %mpd-group.
(mpd-configuration): Remove `group' field.
(mpd-configuration-group): Unexport.
(mpd-group-sanitizer): Delete variable.
(mpd-accounts): Create group if it’s `%mpd-group'.
(mpd-serialize-user-group): Remove.

Change-Id: I0c20c817ba7fd892c96497208ca5338088f74252

1 files changed, 12 insertions, 34 deletions

diff --git a/gnu/services/audio.scm b/gnu/services/audio.scm
index 5091d7fc137..34e858d25d3 100644
--- a/gnu/services/audio.scm
+++ b/gnu/services/audio.scm
@@ -67,7 +67,6 @@
             mpd-configuration?
             mpd-configuration-package
             mpd-configuration-user
-            mpd-configuration-group
             mpd-configuration-shepherd-requirement
             mpd-configuration-log-file
             mpd-configuration-log-level
@@ -173,30 +172,25 @@
 (define (mpd-serialize-user-account field-name value)
   (mpd-serialize-string field-name (user-account-name value)))
 
-(define (mpd-serialize-user-group field-name value)
-  (mpd-serialize-string field-name (user-group-name value)))
-
 (define-maybe string (prefix mpd-))
 (define-maybe list-of-strings (prefix mpd-))
 (define-maybe boolean (prefix mpd-))
 
+(define %mpd-group
+  (user-group
+   (name "mpd")
+   (system? #t)))
+
 (define %mpd-user
   (user-account
    (name "mpd")
-   ;; XXX: This is a place-holder to be lazily substituted in (…-accounts)
-   ;; with the value from the 'group' field of <mpd-configuration>.
-   (group %lazy-group)
+   (group (user-group-name %mpd-group))
    (system? #t)
    (comment "Music Player Daemon (MPD) user")
    ;; MPD can use $HOME (or $XDG_CONFIG_HOME) to place its data.
    (home-directory "/var/lib/mpd")
    (shell (file-append shadow "/sbin/nologin"))))
 
-(define %mpd-group
-  (user-group
-   (name "mpd")
-   (system? #t)))
-
 ;;; TODO: Procedures for deprecated fields, to be removed.
 
 (define mpd-deprecated-fields '((music-dir . music-directory)
@@ -239,17 +233,6 @@ user-account instead~%"))
         (else
          (configuration-field-error #f 'user value))))
 
-(define (mpd-group-sanitizer value)
-  (cond ((user-group? value) value)
-        ((string? value)
-         (warning (G_ "string value for 'group' is deprecated, use \
-user-group instead~%"))
-         (user-group
-          (inherit %mpd-group)
-          (name value)))
-        (else
-         (configuration-field-error #f 'group value))))
-
 (define (mpd-log-file-sanitizer value)
   ;; XXX: While leaving the 'sys_log' option out of the mpd.conf file is
   ;; supposed to cause logging to happen via systemd (elogind provides a
@@ -417,11 +400,6 @@ to be appended to the audio output configuration.")
    "The user to run mpd as."
    (sanitizer mpd-user-sanitizer))
 
-  (group
-   (user-group %mpd-group)
-   "The group to run mpd as."
-   (sanitizer mpd-group-sanitizer))
-
   (shepherd-requirement
    (list-of-symbols '())
    "This is a list of symbols naming Shepherd services that this service
@@ -650,12 +628,12 @@ appended to the configuration.")
                         (format #t "Service MPD is not running.")))))))))))
 
 (define (mpd-accounts config)
-  (match-record config <mpd-configuration> (user group)
-    ;; TODO: Deprecation code, to be removed.
-    (let ((user (if (eq? (user-account-group user) %lazy-group)
-                    (set-user-group user group)
-                    user)))
-      (list user group))))
+  (match-record config <mpd-configuration> (user)
+    `(,user
+      ;; Create %mpd-group if that's what we're using.
+      ,(when (string=? (user-group-name %mpd-group)
+                       (user-account-group user))
+         %mpd-group))))
 
 (define mpd-service-type
   (service-type