emacs-29 6e2923d80f 2/2: Make tab-bar-tab-group-format-function backwards-compatible (bug#60073)

[Juri Linkov]

branch: emacs-29
commit 6e2923d80f822e6da470860f51ba13bcad10d0a3
Author: Juri Linkov <juri@linkov.net>
Commit: Juri Linkov <juri@linkov.net>

    Make tab-bar-tab-group-format-function backwards-compatible (bug#60073)
    
    * lisp/tab-bar.el (tab-bar--format-tab-group): Add condition-case
    with wrong-number-of-arguments for backwards-compatibility.
    (tab-bar-tab-group-format-default): Simplify.
---
 lisp/tab-bar.el | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index 1f25ee6d7e..1baa857e9e 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -844,9 +844,9 @@ Function gets one argument: a tab."
 
 (defcustom tab-bar-tab-group-format-function #'tab-bar-tab-group-format-default
   "Function to format a tab group name.
-Function gets three arguments, a tab with a group name, its
-number and an optional t when the tab is current, and should
-return the formatted tab group name to display in the tab bar."
+Function gets three arguments, a tab with a group name, its number, and
+an optional value that is non-nil when the tab is from the current group.
+It should return the formatted tab group name to display in the tab bar."
   :type 'function
   :initialize 'custom-initialize-default
   :set (lambda (sym val)
@@ -856,12 +856,10 @@ return the formatted tab group name to display in the tab 
bar."
   :version "28.1")
 
 (defun tab-bar-tab-group-format-default (tab i &optional current-p)
-  (let ((name (concat (if tab-bar-tab-hints (format "%d " i) "")
-                      (funcall tab-bar-tab-group-function tab)))
-        (face (if current-p
-                  'tab-bar-tab-group-current
-                'tab-bar-tab-group-inactive)))
-    (propertize name 'face face)))
+  (propertize
+   (concat (if (and tab-bar-tab-hints (not current-p)) (format "%d " i) "")
+           (funcall tab-bar-tab-group-function tab))
+   'face (if current-p 'tab-bar-tab-group-current 
'tab-bar-tab-group-inactive)))
 
 (defcustom tab-bar-tab-group-face-function #'tab-bar-tab-group-face-default
   "Function to define a tab group face.
@@ -884,7 +882,16 @@ when the tab is current.  Return the result as a keymap."
    `((,(intern (format "sep-%i" i)) menu-item ,(tab-bar-separator) ignore))
    `((,(intern (format "group-%i" i))
       menu-item
-      ,(funcall tab-bar-tab-group-format-function tab i current-p)
+      ,(if current-p
+           (condition-case nil
+               (funcall tab-bar-tab-group-format-function tab i current-p)
+             ;; We used to define tab-bar-tab-group-format-function as
+             ;; taking two arguments but after adding the third argument
+             ;; we need to provide backwards-compatibility.
+             (wrong-number-of-arguments
+              (propertize (funcall tab-bar-tab-group-function tab)
+                          'face 'tab-bar-tab-group-current)))
+         (funcall tab-bar-tab-group-format-function tab i))
       ,(if current-p 'ignore
          (or
           (alist-get 'binding tab)