bug#71270: 30.0.50; Execute dired-do-shell-command will encounter 'wrong-type-argument stringp nil' error

[Eli Zaretskii]

> From: Yuwei Tian <fishtai0@gmail.com>
> Date: Thu, 30 May 2024 14:24:35 +0800
> 
> After commit 74f15ad72d937b309dafecba872bccd1a880181e, it will
> encounter 'wrong-type-argument string nil' error when executing
> dired-do-shell-command.
> 
> Here is the backtrace:
> 
>   string-match("/" nil 0)
>   split-string(nil "/")
>   xdg-mime-apps(nil)
>   shell-command-guess-xdg(nil ("xxxxxxx"))
> 
> The shell-command-guess-xdg is being called in the chain of
> shell-command-guess-functions. Here is the definition of
> shell-command-guess-xdg function:
> 
> (defun shell-command-guess-xdg (commands files)
>   "Populate COMMANDS by XDG configuration for FILES."
>   (require 'xdg)
>   (let* ((xdg-mime (when (executable-find "xdg-mime")
>                      (string-trim-right
>                       (shell-command-to-string
>                        (concat "xdg-mime query filetype "
>                                (shell-quote-argument (car files)))))))
>          (xdg-mime-apps (unless (string-empty-p xdg-mime)
>                           (xdg-mime-apps xdg-mime)))
>          (xdg-commands
>           (mapcar (lambda (desktop)
>                     (setq desktop (xdg-desktop-read-file desktop))
>                     (propertize
>                      (replace-regexp-in-string
>                       " .*" "" (gethash "Exec" desktop))
>                      'name (gethash "Name" desktop)))
>                   xdg-mime-apps)))
>     (append xdg-commands commands)))
> 
> xdg-mime will be nil if xdg-mime not found, string-empty-p returns
> nil and xdg-mime-apps will be called with nil.

Thanks, I'm adding Juri to this discussion.