bug#51173: 28.0.60; gnus-article-describe-key doesn't work

[Katsumi Yamaoka]

Hi,

The following example program returns `sh-case' on Emacs 27 and
olders, however to make it work on Emacs 28 and 29 the third
line has to be uncommented.  So does `describe-key' case.

(with-temp-buffer
  (sh-mode)
  ;;(set-window-buffer nil (current-buffer))
  (describe-key-briefly "\C-c\C-c"))

I don't know when/why those commands were changed to require the
buffer (where the keymap is) to be visited in the selected window,
but now `gnus-article-describe-key\(-briefly\)?' doesn't work
because of this.  A patch to gnus-art.el is attached, though the
one that should be fixed might be help.el.

Thanks.

--- gnus-art.el~        2021-10-06 01:11:50.777999500 +0000
+++ gnus-art.el 2021-10-13 01:04:18.073219200 +0000
@@ -6854,19 +6854,24 @@
                       (read-key-sequence "Describe key: ")))
               gnus-article-mode)
   (gnus-article-check-buffer)
-  (if (memq (key-binding key t) '(gnus-article-read-summary-keys
-                                 gnus-article-read-summary-send-keys))
-      (with-current-buffer gnus-article-current-summary
-       (setq unread-command-events
-             (nconc
-              (mapcar (lambda (x) (if (and (integerp x) (>= x 128))
-                                      (list 'meta (- x 128))
-                                    x))
-                      key)
-              unread-command-events))
-       (let ((cursor-in-echo-area t)
-             gnus-pick-mode)
-         (describe-key (read-key-sequence nil t))))
+  (if (and (memq (key-binding key t) '(gnus-article-read-summary-keys
+                                      gnus-article-read-summary-send-keys))
+          (buffer-live-p gnus-article-current-summary))
+      (let ((artbuf (current-buffer)))
+       (unwind-protect
+           (progn
+             (set-window-buffer nil gnus-article-current-summary)
+             (setq unread-command-events
+                   (nconc
+                    (mapcar (lambda (x) (if (and (integerp x) (>= x 128))
+                                            (list 'meta (- x 128))
+                                          x))
+                            key)
+                    unread-command-events))
+             (let ((cursor-in-echo-area t)
+                   gnus-pick-mode)
+               (describe-key (read-key-sequence nil t))))
+         (set-window-buffer nil artbuf)))
     (describe-key key)))
 
 (defun gnus-article-describe-key-briefly (key &optional insert)
@@ -6877,19 +6882,24 @@
                     current-prefix-arg)
               gnus-article-mode)
   (gnus-article-check-buffer)
-  (if (memq (key-binding key t) '(gnus-article-read-summary-keys
-                                 gnus-article-read-summary-send-keys))
-      (with-current-buffer gnus-article-current-summary
-       (setq unread-command-events
-             (nconc
-              (mapcar (lambda (x) (if (and (integerp x) (>= x 128))
-                                      (list 'meta (- x 128))
-                                    x))
-                      key)
-              unread-command-events))
-       (let ((cursor-in-echo-area t)
-             gnus-pick-mode)
-         (describe-key-briefly (read-key-sequence nil t) insert)))
+  (if (and (memq (key-binding key t) '(gnus-article-read-summary-keys
+                                      gnus-article-read-summary-send-keys))
+          (buffer-live-p gnus-article-current-summary))
+      (let ((artbuf (current-buffer)))
+       (unwind-protect
+           (progn
+             (set-window-buffer nil gnus-article-current-summary)
+             (setq unread-command-events
+                   (nconc
+                    (mapcar (lambda (x) (if (and (integerp x) (>= x 128))
+                                            (list 'meta (- x 128))
+                                          x))
+                            key)
+                    unread-command-events))
+             (let ((cursor-in-echo-area t)
+                   gnus-pick-mode)
+               (describe-key-briefly (read-key-sequence nil t) insert)))
+         (set-window-buffer nil artbuf)))
     (describe-key-briefly key insert)))
 
 ;;`gnus-agent-mode' in gnus-agent.el will define it.