bug#53371: 28.0.90; eshell completion error when trying to complete buffer name, args-out-of-range

[Daniel Mendler]

1. Start emacs -Q
2. M-x eshell
3. Enter "ls > #<" for buffer redirection.
4. Pressing TAB results in an args-out-of-range error, see below.

It seems that completing buffer names is not supported. This feature
would be nice to have. However in any case, no args-out-of-range error
should occur.

Debugger entered--Lisp error: (args-out-of-range 41 #<marker at 40 in
*eshell*>)
  eshell-parse-arguments(41 #<marker at 40 in *eshell*>)
  eshell-complete-parse-arguments()
  pcomplete-parse-arguments(nil)
  pcomplete-completions()
  pcomplete-completions-at-point()
  completion--capf-wrapper(pcomplete-completions-at-point all)
  completion-at-point()
  funcall-interactively(completion-at-point)

In GNU Emacs 28.0.90 (build 3, x86_64-pc-linux-gnu, GTK+ Version 3.24.5,
cairo version 1.16.0)
 of 2022-01-01 built on projects
Repository revision: efb1c7ec379430f560c5b801969ae43023c52734
Repository branch: emacs-28
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian GNU/Linux 10 (buster)

Configured using:
 'configure --prefix=/home/user/emacs/install --with-cairo --with-json
 --with-native-compilation --with-xwidgets'

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LIBOTF LIBSELINUX LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG
RSVG SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE XIM XPM
XWIDGETS GTK3 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Debugger

Minor modes in effect:
  shell-dirtrack-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr help-fns radix-tree cl-print debug backtrace
help-mode find-func cus-start cus-load emacsbug message rmc puny dired
dired-loaddefs rfc822 mml mml-sec epa derived epg rfc6068 epg-config
gnus-util rmail rmail-loaddefs auth-source cl-seq eieio eieio-core
cl-macs eieio-loaddefs password-cache json map text-property-search
time-date subr-x mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils em-unix em-term term disp-table shell
ehelp em-script em-prompt em-ls cl-loaddefs cl-lib em-hist em-pred
em-glob em-cmpl em-dirs esh-var pcomplete comint ansi-color ring
em-basic em-banner em-alias esh-mode eshell esh-cmd esh-ext esh-opt
esh-proc esh-io esh-arg esh-module esh-groups esh-util seq byte-opt gv
bytecomp byte-compile cconv iso-transl tooltip eldoc paren electric
uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel
term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
timer select scroll-bar mouse jit-lock font-lock syntax font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite emoji-zwj charscript charprop case-table
epa-hook jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice
button loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote threads xwidget-internal dbusbind
inotify dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit x multi-tty make-network-process
native-compile emacs)

Memory information:
((conses 16 107969 13219)
 (symbols 48 9769 0)
 (strings 32 28542 1249)
 (string-bytes 1 959554)
 (vectors 16 18825)
 (vector-slots 8 358993 17174)
 (floats 8 32 60)
 (intervals 56 315 0)
 (buffers 992 12))