Actually no, it doesn't help in all cases. It got better, but sometimes
still dies with the same error:

Debugger entered--Lisp error: (wrong-type-argument processp nil)
  process-mark(nil)
  (move-marker (process-mark proc) (point) (current-buffer))
  (let ((proc (get-buffer-process (current-buffer)))) (message "@ %S %S"
(current-buffer) proc) (move-marker (process-mark proc) (point)
(current-buffer)) (set-process-filter proc #'find-dired-filter)
(set-process-sentinel proc #'find-dired-sentinel))
  ...

For debugging I also added this line:

     (shell-command (concat command "&") (current-buffer))
     (let ((proc (get-buffer-process (current-buffer))))
 +     (message "@ %S %S" (current-buffer) proc)
       ;; Initialize the process marker; it is used by the filter.
       (move-marker (process-mark proc) (point) (current-buffer))  ;; <--
dies here

Here is the resut in buffer *Messages*:

@ #<buffer *Find*> nil

So, the process can be nil immediately after `shell-command' returns too.

Paul


On Tue, 2 Aug 2022 at 13:28, Lars Ingebrigtsen <larsi@gnus.org> wrote:

> Paul Pogonyshev <pogonyshev@gmail.com> writes:
>
> > Seems so. I guess with the way Elisp works it is even correct, because
> > (as I understand) Elisp has no way to notice that process has died if
> > there are no IO calls between `shell-process' and `set-process-*'.
>
> Yes, but I'm not quite sure that's actually the case in all
> circumstances (especially when Tramp is involved)...
>
> > But it does feel dirty. (Also that `(sit-for 1)' a few lines above
> > feels dirty.)
>
> Yeah, much of the code in find-dired.el looks pretty fragile.
>
> But I guess this works now, so I'm closing this bug report.
>
>