bug#52794: 28.0.90; Eshell: error while completing

[Óscar Fuentes]

emacs -Q

M-x eshell

Go to a directory with two or more files with the same prefix. The Emacs
build directory, for instance. Let's suppose the prefix is `c'.

mv c* foo[TAB]

Debugger entered--Lisp error: (wrong-type-argument stringp ("config.log" 
"config.log~" "config.status"))
  string-match("\\.\\.\\.+/" ("config.log" "config.log~" "config.status"))
  #f(compiled-function (arg) #<bytecode 
0x18cd73f57cbbd741>)((eshell-extended-glob (eshell-convert (concat "c" "*"))))
  mapcar(#f(compiled-function (arg) #<bytecode 0x18cd73f57cbbd741>) ("mv" 
(eshell-extended-glob (eshell-convert (concat "c" "*"))) "l"))
  eshell-complete-parse-arguments()
  pcomplete-parse-arguments(nil)
  pcomplete-completions()
  pcomplete-completions-at-point()
  completion--capf-wrapper(pcomplete-completions-at-point all)
  run-hook-wrapped(completion--capf-wrapper pcomplete-completions-at-point all)
  completion-at-point()
  funcall-interactively(completion-at-point)
  call-interactively(completion-at-point nil nil)
  command-execute(completion-at-point)


The patch below fixes the problem, which if my analysis is correct, was
introduced by:

commit 9224a863192b1317ef307bcc76abfdfbad73b796
Author: Michalis V <mvar.40k@gmail.com>
Date:   Fri Aug 27 18:46:04 2021 +0200

    Fix completion of extended "..." syntax in eshell
    
    * lisp/eshell/em-cmpl.el (eshell-complete-parse-arguments): Expand
    "..." (bug#19626).


emacs/lisp/eshell/em-cmpl.el
@@ -380,7 +380,7 @@
                       (setq val (number-to-string val)))
                      ;; expand .../ etc that only eshell understands to
                      ;; standard ../../
-                     ((string-match "\\.\\.\\.+/" val)
+                     ((and (stringp val) (string-match "\\.\\.\\.+/" val))
                       (setq val (eshell-expand-multiple-dots val))))
                (or val "")))
           args)

The problem is that `val' is a list when more than one file matches the
glob, and then `string-match' errors-out.

Ok to commit in emacs-28 ?