recentf (wrong-type-argument stringp nil)

Question

I seem to have updated something which is causing recentf to fail, not sure.

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  file-readable-p(nil)
  (and (file-readable-p filename) (recentf-include-p filename) filename)
  (lambda (filename) (and (file-readable-p filename) (recentf-include-p filename) filename))(nil)
  mapcar((lambda (filename) (and (file-readable-p filename) (recentf-include-p filename) filename)) (nil))
  (delq nil (mapcar #'(lambda (filename) (and (file-readable-p filename) (recentf-include-p filename) filename)) recentf-list))
  (setq recentf-list (delq nil (mapcar #'(lambda (filename) (and (file-readable-p filename) (recentf-include-p filename) filename)) recentf-list)))
  (let ((count (length recentf-list))) (setq recentf-list (delq nil (mapcar #'(lambda (filename) (and (file-readable-p filename) (recentf-include-p filename) filename)) recentf-list))) (setq count (- count (length recentf-list))) (message "%s removed from the list" (cond ((= count 0) "No file") ((= count 1) "One file") (t (format "%d files" count)))))
  recentf-cleanup()
  (if (eq recentf-auto-cleanup 'enable) (recentf-cleanup))
  (cond (on-p (recentf-rebuild-virtual-pathes) (if recentf-initialized-p nil (setq recentf-initialized-p t) (if (file-readable-p recentf-save-file) (load-file recentf-save-file)) (setq recentf-update-menu-p t) (add-hook 'find-file-hooks 'recentf-add-file-hook) (add-hook 'write-file-hooks 'recentf-add-file-hook) (add-hook (if nil 'activate-menubar-hook 'menu-bar-update-hook) 'recentf-update-menu-hook) (add-hook 'kill-emacs-hook 'recentf-save-list)) (if (eq recentf-auto-cleanup 'enable) (recentf-cleanup))) (recentf-initialized-p (setq recentf-initialized-p nil) (recentf-save-list) (easy-menu-remove-item nil recentf-menu-path recentf-menu-title) (remove-hook 'find-file-hooks 'recentf-add-file-hook) (remove-hook 'write-file-hooks 'recentf-add-file-hook) (remove-hook (if nil 'activate-menubar-hook 'menu-bar-update-hook) 'recentf-update-menu-hook) (remove-hook 'kill-emacs-hook 'recentf-save-list) (recentf-cancel-cleanup-timer)))
  (let ((on-p (if arg (> (prefix-numeric-value arg) 0) (not recentf-mode)))) (cond (on-p (recentf-rebuild-virtual-pathes) (if recentf-initialized-p nil (setq recentf-initialized-p t) (if (file-readable-p recentf-save-file) (load-file recentf-save-file)) (setq recentf-update-menu-p t) (add-hook 'find-file-hooks 'recentf-add-file-hook) (add-hook 'write-file-hooks 'recentf-add-file-hook) (add-hook (if nil 'activate-menubar-hook 'menu-bar-update-hook) 'recentf-update-menu-hook) (add-hook 'kill-emacs-hook 'recentf-save-list)) (if (eq recentf-auto-cleanup 'enable) (recentf-cleanup))) (recentf-initialized-p (setq recentf-initialized-p nil) (recentf-save-list) (easy-menu-remove-item nil recentf-menu-path recentf-menu-title) (remove-hook 'find-file-hooks 'recentf-add-file-hook) (remove-hook 'write-file-hooks 'recentf-add-file-hook) (remove-hook (if nil 'activate-menubar-hook 'menu-bar-update-hook) 'recentf-update-menu-hook) (remove-hook 'kill-emacs-hook 'recentf-save-list) (recentf-cancel-cleanup-timer))) (setq recentf-mode on-p))
  recentf-mode(1)
  eval-buffer(#<buffer  *load*> nil "/home/b0ef/.emacs.d/init.el" nil t)  ; Reading at buffer position 143162
  load-with-code-conversion("/home/b0ef/.emacs.d/init.el" "/home/b0ef/.emacs.d/init.el" t t)
  load("/home/b0ef/.emacs.d/init" noerror nomessage)
  startup--load-user-init-file(#f(compiled-function () #<bytecode -0xfdba33d4b028da0>) #f(compiled-function () #<bytecode -0x1f3c686ddc0cdc35>) t)
  command-line()
  normal-top-level()

If I disable recentf-mode, I seem to get problems with ivy-switch-buffer:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  file-readable-p(nil)
  (and (file-readable-p filename) (recentf-include-p filename) filename)
  (lambda (filename) (and (file-readable-p filename) (recentf-include-p filename) filename))(nil)
  mapcar((lambda (filename) (and (file-readable-p filename) (recentf-include-p filename) filename)) ("/mnt/b53d6116-b84e-4cbb-a7d0-cc1cfb3089d9/ds/platf..." "/mnt/b53d6116-b84e-4cbb-a7d0-cc1cfb3089d9/ds/platf..." "/tmp/foo.txt" nil))
  (delq nil (mapcar #'(lambda (filename) (and (file-readable-p filename) (recentf-include-p filename) filename)) recentf-list))
  (setq recentf-list (delq nil (mapcar #'(lambda (filename) (and (file-readable-p filename) (recentf-include-p filename) filename)) recentf-list)))
  (let ((count (length recentf-list))) (setq recentf-list (delq nil (mapcar #'(lambda (filename) (and (file-readable-p filename) (recentf-include-p filename) filename)) recentf-list))) (setq count (- count (length recentf-list))) (message "%s removed from the list" (cond ((= count 0) "No file") ((= count 1) "One file") (t (format "%d files" count)))))
  recentf-cleanup()
  (if (eq recentf-auto-cleanup 'enable) (recentf-cleanup))
  (cond (on-p (recentf-rebuild-virtual-pathes) (if recentf-initialized-p nil (setq recentf-initialized-p t) (if (file-readable-p recentf-save-file) (load-file recentf-save-file)) (setq recentf-update-menu-p t) (add-hook 'find-file-hooks 'recentf-add-file-hook) (add-hook 'write-file-hooks 'recentf-add-file-hook) (add-hook (if nil 'activate-menubar-hook 'menu-bar-update-hook) 'recentf-update-menu-hook) (add-hook 'kill-emacs-hook 'recentf-save-list)) (if (eq recentf-auto-cleanup 'enable) (recentf-cleanup))) (recentf-initialized-p (setq recentf-initialized-p nil) (recentf-save-list) (easy-menu-remove-item nil recentf-menu-path recentf-menu-title) (remove-hook 'find-file-hooks 'recentf-add-file-hook) (remove-hook 'write-file-hooks 'recentf-add-file-hook) (remove-hook (if nil 'activate-menubar-hook 'menu-bar-update-hook) 'recentf-update-menu-hook) (remove-hook 'kill-emacs-hook 'recentf-save-list) (recentf-cancel-cleanup-timer)))
  (let ((on-p (if arg (> (prefix-numeric-value arg) 0) (not recentf-mode)))) (cond (on-p (recentf-rebuild-virtual-pathes) (if recentf-initialized-p nil (setq recentf-initialized-p t) (if (file-readable-p recentf-save-file) (load-file recentf-save-file)) (setq recentf-update-menu-p t) (add-hook 'find-file-hooks 'recentf-add-file-hook) (add-hook 'write-file-hooks 'recentf-add-file-hook) (add-hook (if nil 'activate-menubar-hook 'menu-bar-update-hook) 'recentf-update-menu-hook) (add-hook 'kill-emacs-hook 'recentf-save-list)) (if (eq recentf-auto-cleanup 'enable) (recentf-cleanup))) (recentf-initialized-p (setq recentf-initialized-p nil) (recentf-save-list) (easy-menu-remove-item nil recentf-menu-path recentf-menu-title) (remove-hook 'find-file-hooks 'recentf-add-file-hook) (remove-hook 'write-file-hooks 'recentf-add-file-hook) (remove-hook (if nil 'activate-menubar-hook 'menu-bar-update-hook) 'recentf-update-menu-hook) (remove-hook 'kill-emacs-hook 'recentf-save-list) (recentf-cancel-cleanup-timer))) (setq recentf-mode on-p))
  recentf-mode(1)
  ivy--virtual-buffers()
  ivy--buffer-list("" (ivy-switch-buffer ivy-switch-buffer-other-window counsel-switch-buffer) nil)
  ivy--reset-state(#s(ivy-state :prompt "Switch to buffer: " :collection internal-complete-buffer :predicate nil :require-match nil :initial-input nil :history nil :preselect "*scratch*" :keymap (keymap (11 . ivy-switch-buffer-kill)) :update-fn nil :sort nil :frame #<frame F1 0x2ad7ee8> :window #<window 1 on *GNU Emacs*> :buffer #<buffer *GNU Emacs*> :text nil :action (1 ("o" ivy--switch-buffer-action "default") ("i" ivy--action-insert "insert") ("w" ivy--action-copy "copy") ("f" ivy--find-file-action "find file") ("j" ivy--switch-buffer-other-window-action "other window") ("k" ivy--kill-buffer-action "kill") ("r" ivy--rename-buffer-action "rename") ("x" counsel-open-buffer-file-externally "open externally")) :unwind nil :re-builder ivy--regex-fuzzy :matcher ivy--switch-buffer-matcher :dynamic-collection nil :display-transformer-fn ivy-switch-buffer-transformer :directory "~/" :caller ivy-switch-buffer :current nil :def nil :ignore t :multi-action nil :extra-props nil))
  ivy-read("Switch to buffer: " internal-complete-buffer :keymap (keymap (11 . ivy-switch-buffer-kill)) :preselect "*scratch*" :action ivy--switch-buffer-action :matcher ivy--switch-buffer-matcher :caller ivy-switch-buffer)
  ivy-switch-buffer()
  funcall-interactively(ivy-switch-buffer)
  call-interactively(ivy-switch-buffer nil nil)
  command-execute(ivy-switch-buffer)

I'm not really sure what I did, cause this worked perfectly before;)

I'm using emacs-28, but to see if it was version related, I just installed emacs-30 from git and I have the same problem there.

Ok, thanks to the help, I figured it out.

I had to delete ~/.recentf, which I had already done, but I had to do it once more, for whatever reason.

BTW: Any way I can specify where this file should be, so that I can back it up?

This is a stupid problem; how can this happen?

less .recentf-wtf2
;;; Automatically generated by `recentf' on Sat Feb 25 21:51:10 2023.
(setq recentf-list
      '(
        "/mnt/b53d6116-b84e-4cbb-a7d0-cc1cfb3089d9/ds/platform/conf/home.dot.emacs.dot.d.emacsen.org"
        "/tmp/wtf.org"
        "/mnt/b53d6116-b84e-4cbb-a7d0-cc1cfb3089d9/ds/platform/conf/home.dot.emacs.dot.d.emacsen.el"
        "/tmp/foo.txt"
        nil
        ))
(setq recentf-filter-changer-state
      '(
        nil
        ))

Answer 1

Bisect your init file to find the culprit.

For some reason, your initial value of recentf-list is (nil); that is, it contains nil, which is not a file name (not a string). If there are no file names then the list should just be empty: () (aka nil).