bug#70322: 30.0.50; format-seconds with %z doesn't handle zero input correctly

[Stephen Berman via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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On Wed, 10 Apr 2024 11:59:42 +0200 Herman@debbugs.gnu.org, Géza <geza.herman@gmail.com> wrote:

> When the input seconds is 0, format-seconds emits the full string. For
> example,
>
> (format-seconds "%Y, %D, %H, %M, %z%S" 0)
>
> returns "0 years, 0 days, 0 hours, 0 minutes, 0 seconds"
>
> instead of "0 seconds".
>
> (format-seconds "%Y, %D, %H, %M, %z%S" 1) correctly returns "1 second".

The attached patch seems to fix this.

Steve Berman


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diff --git a/lisp/calendar/time-date.el b/lisp/calendar/time-date.el
index e96e2e7e2db..59e236ce3c5 100644
--- a/lisp/calendar/time-date.el
+++ b/lisp/calendar/time-date.el
@@ -352,9 +352,13 @@ format-seconds
           ;; Cf article-make-date-line in gnus-art.
           (setq num (floor seconds unit)
                 seconds (- seconds (* num unit)))
-          (let ((is-zero (zerop (if (= unit 1)
-                                    (+ num fraction)
-                                  num))))
+          (let ((is-zero (if (and (zerop seconds) (= unit 1))
+                             ;; Also drop leading units when SECONDS is
+                             ;; 0 (bug#70322).
+                             nil
+                           (zerop (if (= unit 1)
+                                      (+ num fraction)
+                                    num)))))
             ;; Start position of the first non-zero unit.
             (when (and (not leading-zeropos)
                        (not is-zero))