"Cannot make side window the only window" on persp-restore-window-conf

[hlissner]

If the current window is a side window, and you attempt to switch perspectives (via persp-switch), the following error occurs: Cannot make side window the only window, leaving persp-mode in a broken state.

• side windows are a new feature in Emacs 26. They can be detected via the window-side window parameter and opened with display-buffer-in-side-window.
• The error is caused by calling delete-other-windows from a side window.
• The error originates from persp-restore-window-conf, which calls delete-other-windows on line 3567.

Steps to reproduce

1. Opens Emacs 26+
2. Create a new perspective: (persp-add-new "X") (don't switch to it)
3. Create and select the side window:

   (let* ((buffer (get-buffer-create "*temp*"))
        (window (display-buffer-in-side-window buffer '((side . bottom)))))
   (select-window window))

4. Switch to the "X" workspace via M-x persp-switch.

---

I'm not sure how you want to handle this edge case. The workaround I am currently using is:

  (defun select-non-side-window (&rest _)
    "Ensure a side window isn't current when switching workspaces."
    (when (window-parameter nil 'window-side)
      (select-window
       (cl-loop for win in (window-list)
                unless (window-parameter win 'window-side)
                return win))))
  (add-hook 'persp-before-deactivate-functions #'select-non-side-window)

[Bad-ptr]

Thanks for detailed bug report. Can you test the develop branch fea610580fc748125dd431d9173cded14394f9b1 ?

[hlissner]

Sorry for the late reply. fea6105 has been working without issue!

[Bad-ptr]

ok, then it must be fixed