Subject: bug#49931: 28.0.50; `choose-completion' submits incorrect string when minibuffer content changes after creation of the *Completions* buffer

From: Visuwesh <[email-masked]>
Date: Sat, 7 Aug 2021 19:20:35 +0200 (CEST)

When one edits the minibuffer content after the creation of
*Completions* buffer, `choose-completion' incorrectly submits the wrong
string to the command upon selecting a candidate.  To reproduce,

1. Start emacs -Q.
2. Type the following key sequence: C-h f emacs- TAB.
3. Type a.
4. Select `emacs-bzr-get-version' from the *Completions* buffer.
5. "user-error: Symbol’s function definition is void:
emacs-bzr-get-versiona" is shown in the echo area.

What I expected to happen:

I expected `choose-completion' to submit "emacs-bzr-get-version" to
describe-function, not "emacs-bzr-get-versiona".

Regards.

[  P.S. Please add me to the CCs since I'm not subscribed to the mailing
list.  ]

In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.27, cairo version 1.16.0)
Repository revision: 0b049fe71d73f6885a3c81ea31829e3befc18933
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: NixOS 21.11 (Porcupine)

Configured using:
'configure
--prefix=/nix/store/6gh7ijbrfaahs78syqhjc6f2y7gi76h2-emacs-git-20210806.0
--disable-build-details --with-modules --with-x-toolkit=gtk3 --with-xft
--with-cairo'

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY INOTIFY
PDUMPER PNG RSVG SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE
XIM XPM GTK3 ZLIB

Important settings:
  value of $EMACSLOADPATH:
  value of $EMACSNATIVELOADPATH: /nix/store/ld3lv1bbi9zx15k3h5hni467gyqxckjr-emacs-packages-deps/share/emacs/native-lisp::
  value of $LANG: en_GB.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-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
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg 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 seq byte-opt
gv bytecomp byte-compile cconv mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils time-date subr-x thingatpt
help-fns radix-tree help-mode cl-loaddefs cl-lib iso-transl tooltip
eldoc electric uniquify ediff-hook vc-hooks lisp-float-type 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 elisp-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 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 dbusbind
inotify dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 59485 9215)
(symbols 48 6917 1)
(strings 32 21260 1804)
(string-bytes 1 666531)
(vectors 16 14618)
(vector-slots 8 188838 7589)
(floats 8 21 50)
(intervals 56 398 0)
(buffers 992 11))