services: mcron: Add log? and log-format fields to mcron-configuration.

* gnu/services/mcron.scm (list-of-gexps?): New predicate.
(mcron-configuration): Rewrite using define-configuration.
[log?, log-format]: New fields.
(mcron-shepherd-services): Invoke mcron with the --log and --log-format
arguments when log? is #t,
(generate-doc): New procedure.
* doc/guix.texi (Scheduled Job Execution): Update doc.
(Mcron Home Service): Likewise.
* gnu/home/services/mcron.scm: Keep in sync with the above changes to
gnu/services/mcron.scm.

3 files changed, 108 insertions, 31 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 4d974be53e..ef3b8e127e 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -19019,20 +19019,33 @@ words, it is possible to define services that provide additional mcron
 jobs to run.
 @end defvr
 
+@c Generated via (generate-documentation) at the bottom of (gnu services
+@c mcron).
+@c %start of fragment
 @deftp {Data Type} mcron-configuration
-Data type representing the configuration of mcron.
+Available @code{mcron-configuration} fields are:
 
 @table @asis
-@item @code{mcron} (default: @var{mcron})
+@item @code{mcron} (default: @code{mcron}) (type: file-like)
 The mcron package to use.
 
-@item @code{jobs}
+@item @code{jobs} (default: @code{()}) (type: list-of-gexps)
 This is a list of gexps (@pxref{G-Expressions}), where each gexp
 corresponds to an mcron job specification (@pxref{Syntax, mcron job
-specifications,, mcron, GNU@tie{}mcron}).
+specifications,, mcron,GNU@tie{}mcron}).
+
+@item @code{log?} (default: @code{#t}) (type: boolean)
+Log messages to standard output.
+
+@item @code{log-format} (default: @code{"~1@@*~a ~a: ~a~%"}) (type: string)
+@code{(ice-9 format)} format string for log messages.  The default value
+produces messages like "@samp{@var{pid} @var{name}: @var{message}"}
+(@pxref{Invoking mcron, Invoking,, mcron,GNU@tie{}mcron}).  Each message
+is also prefixed by a timestamp by GNU Shepherd.
+
 @end table
 @end deftp
-
+@c %end of fragment
 
 @node Log Rotation
 @subsection Log Rotation
@@ -41068,18 +41081,32 @@ jobs to run.
 @end defvr
 
 @deftp {Data Type} home-mcron-configuration
-Data type representing the configuration of mcron.
+Available @code{home-mcron-configuration} fields are:
 
+@c Auto-generated with (gnu home services mcron)'s
+@c generate-documentation procedure.
+@c %start of fragment
 @table @asis
-@item @code{mcron} (default: @var{mcron})
+@item @code{mcron} (default: @code{mcron}) (type: file-like)
 The mcron package to use.
 
-@item @code{jobs}
+@item @code{jobs} (default: @code{()}) (type: list-of-gexps)
 This is a list of gexps (@pxref{G-Expressions}), where each gexp
 corresponds to an mcron job specification (@pxref{Syntax, mcron job
-specifications,, mcron, GNU@tie{}mcron}).
+specifications,, mcron,GNU@tie{}mcron}).
+
+@item @code{log?} (default: @code{#t}) (type: boolean)
+Log messages to standard output.
+
+@item @code{log-format} (default: @code{"~1@@*~a ~a: ~a~%"}) (type: string)
+@code{(ice-9 format)} format string for log messages.  The default value
+produces messages like "@samp{@var{pid} @var{name}: @var{message}"}
+(@pxref{Invoking mcron, Invoking,, mcron,GNU@tie{}mcron}).  Each message
+is also prefixed by a timestamp by GNU Shepherd.
+
 @end table
 @end deftp
+@c %end of fragment
 
 @node Power Management Home Services
 @subsection Power Management Home Services
diff --git a/gnu/home/services/mcron.scm b/gnu/home/services/mcron.scm
index 0b3dbb810b..1d294a997c 100644
--- a/gnu/home/services/mcron.scm
+++ b/gnu/home/services/mcron.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
 ;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;; Copyright © 2022 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -20,6 +21,7 @@
 (define-module (gnu home services mcron)
   #:use-module (gnu packages guile-xyz)
   #:use-module (gnu home services)
+  #:use-module (gnu services configuration)
   #:use-module (gnu services shepherd)
   #:use-module (gnu home services shepherd)
   #:use-module (guix records)
@@ -53,13 +55,23 @@
 ;;
 ;;; Code:
 
-(define-record-type* <home-mcron-configuration> home-mcron-configuration
-  make-home-mcron-configuration
-  home-mcron-configuration?
-  (package home-mcron-configuration-package ; package
-           (default mcron))
-  (jobs home-mcron-configuration-jobs   ; list of jobs
-        (default '())))
+(define list-of-gexps?
+  (list-of gexp?))
+
+(define-configuration/no-serialization home-mcron-configuration
+  (mcron (file-like mcron) "The mcron package to use.")
+  (jobs
+   (list-of-gexps '())
+   "This is a list of gexps (@pxref{G-Expressions}), where each gexp
+corresponds to an mcron job specification (@pxref{Syntax, mcron job
+specifications,, mcron, GNU@tie{}mcron}).")
+  (log? (boolean #t) "Log messages to standard output.")
+  (log-format
+   (string "~1@*~a ~a: ~a~%")
+   "@code{(ice-9 format)} format string for log messages.  The default value
+produces messages like \"@samp{@var{pid} @var{name}:
+@var{message}\"} (@pxref{Invoking mcron, Invoking,, mcron, GNU@tie{}mcron}).
+Each message is also prefixed by a timestamp by GNU Shepherd."))
 
 (define job-files (@@ (gnu services mcron) job-files))
 (define shepherd-schedule-action
@@ -69,19 +81,23 @@
   (match-lambda
     (($ <home-mcron-configuration> mcron '()) ; no jobs to run
      '())
-    (($ <home-mcron-configuration> mcron jobs)
+    (($ <home-mcron-configuration> mcron jobs  log? log-format)
      (let ((files (job-files mcron jobs)))
        (list (shepherd-service
               (documentation "User cron jobs.")
               (provision '(mcron))
               (modules `((srfi srfi-1)
                          (srfi srfi-26)
-                         (ice-9 popen)            ; for the 'schedule' action
+                         (ice-9 popen)  ; for the 'schedule' action
                          (ice-9 rdelim)
                          (ice-9 match)
                          ,@%default-modules))
               (start #~(make-forkexec-constructor
-                        (list #$(file-append mcron "/bin/mcron") #$@files)
+                        (list (string-append #$mcron "/bin/mcron")
+                              #$@(if log?
+                                     #~("--log" "--log-format" #$log-format)
+                                     #~())
+                              #$@files)
                         #:log-file (string-append
                                     (or (getenv "XDG_LOG_HOME")
                                         (format #f "~a/.local/var/log"
@@ -91,7 +107,7 @@
               (actions
                (list (shepherd-schedule-action mcron files)))))))))
 
-(define home-mcron-profile (compose list home-mcron-configuration-package))
+(define home-mcron-profile (compose list home-mcron-configuration-mcron))
 
 (define (home-mcron-extend config jobs)
   (home-mcron-configuration
@@ -113,3 +129,12 @@
                 (default-value (home-mcron-configuration))
                 (description
                  "Install and configure the GNU mcron cron job manager.")))
+
+
+;;;
+;;; Generate documentation.
+;;;
+(define (generate-doc)
+  (configuration->documentation 'home-mcron-configuration))
+
+;;; mcron.scm ends here
diff --git a/gnu/services/mcron.scm b/gnu/services/mcron.scm
index 23760ebda4..52332d6123 100644
--- a/gnu/services/mcron.scm
+++ b/gnu/services/mcron.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2016, 2017, 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2022 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -18,6 +19,7 @@
 
 (define-module (gnu services mcron)
   #:use-module (gnu services)
+  #:use-module (gnu services configuration)
   #:use-module (gnu services shepherd)
   #:use-module (gnu packages guile-xyz)
   #:use-module (guix deprecation)
@@ -30,6 +32,8 @@
             mcron-configuration?
             mcron-configuration-mcron
             mcron-configuration-jobs
+            mcron-configuration-log?
+            mcron-configuration-log-format
 
             mcron-service-type))
 
@@ -48,13 +52,23 @@
 ;;;
 ;;; Code:
 
-(define-record-type* <mcron-configuration> mcron-configuration
-  make-mcron-configuration
-  mcron-configuration?
-  (mcron             mcron-configuration-mcron    ;file-like
-                     (default mcron))
-  (jobs              mcron-configuration-jobs     ;list of <mcron-job>
-                     (default '())))
+(define list-of-gexps?
+  (list-of gexp?))
+
+(define-configuration/no-serialization mcron-configuration
+  (mcron (file-like mcron) "The mcron package to use.")
+  (jobs
+   (list-of-gexps '())
+   "This is a list of gexps (@pxref{G-Expressions}), where each gexp
+corresponds to an mcron job specification (@pxref{Syntax, mcron job
+specifications,, mcron, GNU@tie{}mcron}).")
+  (log? (boolean #t) "Log messages to standard output.")
+  (log-format
+   (string "~1@*~a ~a: ~a~%")
+   "@code{(ice-9 format)} format string for log messages.  The default value
+produces messages like \"@samp{@var{pid} @var{name}:
+@var{message}\"} (@pxref{Invoking mcron, Invoking,, mcron, GNU@tie{}mcron}).
+Each message is also prefixed by a timestamp by GNU Shepherd."))
 
 (define (job-files mcron jobs)
   "Return a list of file-like object for JOBS, a list of gexps."
@@ -124,21 +138,25 @@ files."
 
 (define mcron-shepherd-services
   (match-lambda
-    (($ <mcron-configuration> mcron ())           ;nothing to do!
+    (($ <mcron-configuration> mcron ()) ;nothing to do!
      '())
-    (($ <mcron-configuration> mcron jobs)
+    (($ <mcron-configuration> mcron jobs log? log-format)
      (let ((files (job-files mcron jobs)))
        (list (shepherd-service
               (provision '(mcron))
               (requirement '(user-processes))
               (modules `((srfi srfi-1)
                          (srfi srfi-26)
-                         (ice-9 popen)            ;for the 'schedule' action
+                         (ice-9 popen)  ;for the 'schedule' action
                          (ice-9 rdelim)
                          (ice-9 match)
                          ,@%default-modules))
               (start #~(make-forkexec-constructor
-                        (list (string-append #$mcron "/bin/mcron") #$@files)
+                        (list (string-append #$mcron "/bin/mcron")
+                              #$@(if log?
+                                     #~("--log" "--log-format" #$log-format)
+                                     #~())
+                              #$@files)
 
                         ;; Disable auto-compilation of the job files and set a
                         ;; sane value for 'PATH'.
@@ -172,4 +190,11 @@ files."
                                          jobs)))))
                 (default-value (mcron-configuration)))) ;empty job list
 
+
+;;;
+;;; Generate documentation.
+;;;
+(define (generate-doc)
+  (configuration->documentation 'mcron-configuration))
+
 ;;; mcron.scm ends here