[bug#50982] [PATCH] scripts: home/system: Don’t throw an error if no generations exist.

[Xinglu Chen]

Previously, When running ‘guix home describe’ or ‘guix system describe’ prior
to having any generations, a backtrace would produced.  Since not having any
existing generations is not an error, a warning would be enough.

  $ guix system describe
  guix system: warning: no system generation, nothing to describe

* guix/scripts/home.scm (process-command): Produce a warning instead of an
error if no generations exist.
* guix/scripts/system.scm (process-command): Likewise.

Fixes: <https://issues.guix.gnu.org/50978>
Reported-by: Maxime Devos <maximedevos@telenet.be>
---
 guix/scripts/home.scm   | 2 +-
 guix/scripts/system.scm | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/guix/scripts/home.scm b/guix/scripts/home.scm
index 75df6d707d..70860564eb 100644
--- a/guix/scripts/home.scm
+++ b/guix/scripts/home.scm
@@ -260,7 +260,7 @@ (define-syntax-rule (with-store* store exp ...)
     ((describe)
      (match (generation-number %guix-home)
        (0
-        (error (G_ "no home environment generation, nothing to describe~%")))
+        (warning (G_ "no home environment generation, nothing to describe~%")))
        (generation
         (display-home-environment-generation generation))))
     ((list-generations)
diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index 65eb98e4b2..d77d3ea289 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -1307,7 +1307,7 @@ (define-syntax-rule (with-store* store exp ...)
     ((describe)
      (match (generation-number %system-profile)
        (0
-        (error (G_ "no system generation, nothing to describe~%")))
+        (warning (G_ "no system generation, nothing to describe~%")))
        (generation
         (display-system-generation generation))))
     ((search)

base-commit: f1a3c11407b52004e523ec5de20d326c5661681f
-- 
2.33.0