[bug#74955] [PATCH] services: rootless-podman-service-type: Allow not installing podman.

[Tomas Volf <~@wolfsden.cz>]

Sometimes you would want to skip on actually installing the podman package in
order to save disk space and bandwidth.  Even without installing it globally,
podman can still be fetched via guix shell when required.

* gnu/services/containers.scm (package-or-#f?): New procedure.
(rootless-podman-configuration)<podman>: Change type to package-or-#f.
(rootless-podman-service-profile): Produce empty list if not podman package.
* doc/guix.texi (Miscellaneous Services): Document the change.

Change-Id: If533d913ea190558ce7e206d98ada4d805270594
---
 doc/guix.texi               |  3 ++-
 gnu/services/containers.scm | 13 +++++++++----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index f7b7569887..36bab360b4 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -41369,8 +41369,9 @@ Miscellaneous Services
 Available @code{rootless-podman-configuration} fields are:
 
 @table @asis
-@item @code{podman} (default: @code{podman}) (type: package)
+@item @code{podman} (default: @code{podman}) (type: package-of-#f)
 The Podman package that will be installed in the system profile.
+@code{#f} can be passed to suppress the installation.
 
 @item @code{group-name} (default: @code{"cgroup"}) (type: string)
 The name of the group that will own /sys/fs/cgroup resources.  Users that
diff --git a/gnu/services/containers.scm b/gnu/services/containers.scm
index 03f0649c0d..a3cdead0c3 100644
--- a/gnu/services/containers.scm
+++ b/gnu/services/containers.scm
@@ -63,10 +63,15 @@ (define list-of-pam-limits-entries?
 (define list-of-subid-ranges?
   (list-of subid-range?))
 
+(define (package-or-#f? val)
+  (or (not val)
+      (package? val)))
+
 (define-configuration/no-serialization rootless-podman-configuration
   (podman
-   (package podman)
-   "The Podman package that will be installed in the system profile.")
+   (package-or-#f podman)
+   "The Podman package that will be installed in the system profile.
+@code{#f} can be passed to suppress the installation.")
   (group-name
    (string "cgroup")
    "The name of the group that will own /sys/fs/cgroup resources.  Users that
@@ -106,8 +111,8 @@ (define-configuration/no-serialization rootless-podman-configuration
 
 (define rootless-podman-service-profile
   (lambda (config)
-    (list
-     (rootless-podman-configuration-podman config))))
+    (or (and=> (rootless-podman-configuration-podman config) list)
+        (list))))
 
 (define rootless-podman-service-etc
   (lambda (config)
-- 
2.46.0