[bug#62298] [PATCH 7/8] services: mpd: Use user-account (resp. user-group) for user (resp. group) fields.

[Bruno Victal]

Deprecate using strings for these fields and prefer user-account (resp. 
user-group)
instead to avoid duplication within account-service-type.
If a string value is encountered, it is ignored and a predefined variable
is used instead. This is essentially a rollback to how it used to be before
'5c5f0fc1135ff15f9c4adfc5f27eadd9a592b5d1'.

Fixes #61570 <https://issues.guix.gnu.org/61570>.


* gnu/services/audio.scm (mpd-serialize-user-account, mpd-serialize-user-group)
(mpd-user-sanitizer, mpd-group-sanitizer): New procedure.
(%mpd-user, %mpd-group): New variable.
(mpd-configuration)[user, group]: Set value type to user-account (resp. 
user-group).
(mpd-shepherd-service): Adapt for user-account values in user field.
(mpd-accounts): Adapt for user-account (resp. user-group) in user (resp. group) 
field.

* doc/guix.texi (Audio Services): Update documentation.
---
 doc/guix.texi          |  4 +--
 gnu/services/audio.scm | 70 ++++++++++++++++++++++++++++++++----------
 2 files changed, 55 insertions(+), 19 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index df424c561f..ecc520397c 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -33464,10 +33464,10 @@ Audio Services
 @item @code{package} (default: @code{mpd}) (type: file-like)
 The MPD package.
 
-@item @code{user} (default: @code{"mpd"}) (type: string)
+@item @code{user} (type: maybe-user-account)
 The user to run mpd as.
 
-@item @code{group} (default: @code{"mpd"}) (type: string)
+@item @code{group} (type: maybe-user-group)
 The group to run mpd as.
 
 @item @code{shepherd-requirement} (default: @code{()}) (type: list-of-symbol)
diff --git a/gnu/services/audio.scm b/gnu/services/audio.scm
index 0682367358..eaee9b1536 100644
--- a/gnu/services/audio.scm
+++ b/gnu/services/audio.scm
@@ -164,9 +164,32 @@ (define mpd-serialize-boolean mpd-serialize-field)
 (define (mpd-serialize-list-of-strings field-name value)
   #~(string-append #$@(map (cut mpd-serialize-string field-name <>) value)))
 
+(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-maybe user-account (prefix mpd-))
+(define-maybe user-group (prefix mpd-))
+
+(define %mpd-user
+  (user-account
+      (name "mpd")
+      (group "mpd")
+      (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.
 
@@ -197,6 +220,26 @@ (define (mpd-serialize-port field-name value)
 
 (define-maybe port (prefix mpd-))
 
+;;; procedures for unsupported value types, to be removed.
+
+(define (mpd-user-sanitizer value)
+  (cond ((user-account? value) value)
+        ((string? value)
+         (warning (G_ "string value for 'user' is not supported, use \
+user-account instead. Ignoring this value~%"))
+         %mpd-user)
+        (else
+         (leave (G_ "'~a' is not a valid value for 'user'~%") value))))
+
+(define (mpd-group-sanitizer value)
+  (cond ((user-group? value) value)
+        ((string? value)
+         (warning (G_ "string value for 'group' is not supported, use \
+user-group instead. Ignoring this value~%"))
+         %mpd-group)
+        (else
+         (leave (G_ "'~a' is not a valid value for 'group'~%") value))))
+
 ;;;
 
 ;; Generic MPD plugin record, lists only the most prevalent fields.
@@ -347,12 +390,14 @@ (define-configuration mpd-configuration
    empty-serializer)
 
   (user
-   (string "mpd")
-   "The user to run mpd as.")
+   (maybe-user-account %mpd-user)
+   "The user to run mpd as."
+   (sanitizer mpd-user-sanitizer))
 
   (group
-   (string "mpd")
-   "The group to run mpd as.")
+   (maybe-user-group %mpd-group)
+   "The group to run mpd as."
+   (sanitizer mpd-group-sanitizer))
 
   (shepherd-requirement
    (list-of-symbol '())
@@ -516,7 +561,8 @@ (define (mpd-shepherd-service config)
                                             log-file playlist-directory
                                             db-file state-file sticker-file
                                             environment-variables)
-    (let* ((config-file (mpd-serialize-configuration config)))
+    (let ((config-file (mpd-serialize-configuration config))
+          (username (user-account-name user)))
       (shepherd-service
        (documentation "Run the MPD (Music Player Daemon)")
        (requirement `(user-processes loopback ,@shepherd-requirement))
@@ -525,7 +571,7 @@ (define (mpd-shepherd-service config)
                   (and=> #$(maybe-value log-file)
                          (compose mkdir-p dirname))
 
-                  (let ((user (getpw #$user)))
+                  (let ((user (getpw #$username)))
                     (for-each
                      (lambda (x)
                        (when (and x (not (file-exists? x)))
@@ -559,17 +605,7 @@ (define (mpd-shepherd-service config)
 
 (define (mpd-accounts config)
   (match-record config <mpd-configuration> (user group)
-    (list (user-group
-           (name group)
-           (system? #t))
-          (user-account
-           (name user)
-           (group 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"))))))
+    (list user group)))
 
 (define mpd-service-type
   (service-type
-- 
2.39.1