time-stamp: fix minor bug when parsing option combos

* lisp/time-stamp.el (time-stamp-string-preprocess): Handle digit
options correctly to avoid overcounting colon options.

* test/lisp/time-stamp-tests.el (time-stamp-format-time-zone-offset):
Add a new test case that would have caught the option-parsing error.

2 files changed, 5 insertions, 2 deletions

diff --git a/lisp/time-stamp.el b/lisp/time-stamp.el
index 42455ddfe33..0cc566f0d8c 100644
--- a/lisp/time-stamp.el
+++ b/lisp/time-stamp.el
@@ -499,7 +499,8 @@ and all `time-stamp-format' compatibility."
                                 (< ind fmt-len)))
                          (if (and (<= ?0 cur-char) (>= ?9 cur-char))
                              ;; get format width
-                             (let ((field-index ind))
+                             (let ((field-index ind)
+                                   (first-digit cur-char))
                                (while (progn
                                         (setq ind (1+ ind))
                                         (setq cur-char (if (< ind fmt-len)
@@ -510,6 +511,7 @@ and all `time-stamp-format' compatibility."
                                (setq field-width
                                      (substring format field-index ind))
                                (setq ind (1- ind))
+                               (setq cur-char first-digit)
                                t))))
               (setq prev-char cur-char)
               ;; some characters we actually use
diff --git a/test/lisp/time-stamp-tests.el b/test/lisp/time-stamp-tests.el
index c0213536303..b42271e4e51 100644
--- a/test/lisp/time-stamp-tests.el
+++ b/test/lisp/time-stamp-tests.el
@@ -525,7 +525,7 @@
       (should (equal (time-stamp-string "%#Z" ref-time1) utc-abbr)))))
 
 (ert-deftest time-stamp-format-time-zone-offset ()
-  "Test time-stamp format %z."
+  "Tests time-stamp legacy format %z and new offset format %5z."
   (with-time-stamp-test-env
     (let ((utc-abbr (format-time-string "%#Z" ref-time1 t)))
     ;; documented 1995-2019, warned since 2019, will change
@@ -544,6 +544,7 @@
     (should (equal (time-stamp-string "%_z" ref-time1) "+0000"))
     (should (equal (time-stamp-string "%:z" ref-time1) "+00:00"))
     (should (equal (time-stamp-string "%::z" ref-time1) "+00:00:00"))
+    (should (equal (time-stamp-string "%9::z" ref-time1) "+00:00:00"))
     (should (equal (time-stamp-string "%:::z" ref-time1) "+00"))))
 
 (ert-deftest time-stamp-format-non-date-conversions ()