bug#46904: Non-unique windows produced by window-state-put

[Juri Linkov]

>>> It couldn't
>>> possibly harm unless the root window is too small to get split and we
>>> want to put only one window there; so we should handle that special case.
>>
>> I'll try this, thanks.
>
> I'd first try a vertical, then a horizontal split.  Give up if both
> fail.

Maybe something like this:

diff --git a/lisp/window.el b/lisp/window.el
index cfd9876ed0..d750e16626 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -6229,10 +6229,15 @@ window-state-put
                               (throw 'live window)))
                           root))
                      (selected-window)))
-      (delete-other-windows-internal window root)
-      ;; Create a new window to replace the existing one.
-      (setq window (prog1 (split-window window)
-                     (delete-window window)))))
+      (delete-other-windows-internal window root)))
+
+  ;; Create a new window to replace the existing one.
+  (let ((new-window
+         (or (ignore-errors (split-window (selected-window)))
+             (ignore-errors (split-window (selected-window) nil t)))))
+    (when new-window
+      (delete-window window)
+      (setq window new-window)))
 
   (set-window-dedicated-p window nil)