bug#50209: 27.2; eshell-command not working async

[Thierry Volpiatto]

When running a command in eshell ending with "&" the command should not
block emacs, it should run asynchronously.
It seems it is broken since 2005:

  ;; 6b6f91b357f6fe2f1e0d72f046a1b8d8a2d6d8c3
  ;; Author:     John Wiegley <johnw@newartisans.com>
  ;; AuthorDate: Fri May 27 02:57:18 2005 +0000
  ;; Commit:     John Wiegley <johnw@newartisans.com>
  ;; CommitDate: Fri May 27 02:57:18 2005 +0000

To allow my eshell aliases ending with "&" working in helm-find-files I
use this advice:

    (defun helm--advice-eshell-eval-command (command &optional input)
      "Fix return value when command ends with \"&\"."
      ;; Fix this emacs commit which is plain wrong as it returns
      ;; either nil or an error (double because format spec doesn't
      ;; always match specifier) whereas it should return either a
      ;; single element (CAR DELIM) or DELIM itself if the car of
      ;; DELIM is a process.
      ;; This prevent running eshell-command async when needed i.e. when
      ;; command ends with "&".
      ;;
      ;; 6b6f91b357f6fe2f1e0d72f046a1b8d8a2d6d8c3
      ;; Author:     John Wiegley <johnw@newartisans.com>
      ;; AuthorDate: Fri May 27 02:57:18 2005 +0000
      ;; Commit:     John Wiegley <johnw@newartisans.com>
      ;; CommitDate: Fri May 27 02:57:18 2005 +0000
      (if eshell-current-command
          ;; we can just stick the new command at the end of the current
          ;; one, and everything will happen as it should
          (setcdr (last (cdr eshell-current-command))
              (list `(let ((here (and (eobp) (point))))
                           ,(and input
                                 `(insert-and-inherit ,(concat input "\n")))
                           (if here
                               (eshell-update-markers here))
                           (eshell-do-eval ',command))))
        (and eshell-debug-command
             (with-current-buffer (get-buffer-create "*eshell last cmd*")
               (erase-buffer)
               (insert "command: \"" input "\"\n")))
        (setq eshell-current-command command)
        (let* ((delim (catch 'eshell-incomplete
                    (eshell-resume-eval)))
               (val (car-safe delim)))
          ;; If the return value of `eshell-resume-eval' is wrapped in a
          ;; list, it indicates that the command was run asynchronously.
          ;; In that case, unwrap the value before checking the delimiter
          ;; value.
          (if (and val
                   (not (processp val))
                   (not (eq val t)))
              (error "Unmatched delimiter: %S" val)
            ;; Eshell-command expect a list like (<process>) to know if the
            ;; command should be async or not.
            (or (and (processp val) delim) val)))))



In GNU Emacs 27.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30, cairo 
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-- 
Thierry