bug#50675: pcomplete capf fails inside strings

[meedstrom--- via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Steps to reproduce:

1. Launch emacs -Q
2. Type M-x eshell RET
3. Type a quotation mark "
4. Type TAB

Results in "Warning: pcomplete-completions-at-point failed to return valid completion data!" and a tab character is inserted.

Might be considered two separate bugs because when a CAPF fails, it should not insert a tab character?  A consequence of inserting one is that when a package like corfu in auto mode (https://github.com/minad/corfu) tries to call a CAPF on nearly every keystroke, I get lots of tab characters.

Martin Edström


In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, cairo version 1.16.0)
Windowing system distributor 'Configured using:
 'configure
 CONFIG_SHELL=/gnu/store/pwcp239kjf7lnj5i4lkdzcfcxwcfyk72-bash-minimal-5.0.16/bin/bash
 SHELL=/gnu/store/pwcp239kjf7lnj5i4lkdzcfcxwcfyk72-bash-minimal-5.0.16/bin/bash
 --prefix=/gnu/store/j1bci192j9n8bdr7m78asn71izfspmvw-emacs-pgtk-native-comp-28.0.50-206.7b62cfc
 --enable-fast-install --with-native-compilation --with-pgtk
 --with-xwidgets --with-modules --with-cairo --disable-build-details'

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

Important settings:
  value of $EMACSLOADPATH: /home/kept/guix-profiles/emacs/emacs/share/emacs/site-lisp:/gnu/store/j1bci192j9n8bdr7m78asn71izfspmvw-emacs-pgtk-native-comp-28.0.50-206.7b62cfc/share/emacs/28.0.50/lisp:/gnu/store/j1bci192j9n8bdr7m78asn71izfspmvw-emacs-pgtk-native-comp-28.0.50-206.7b62cfc/share/emacs/28.0.50/lisp
  value of $LANG: en_DK.utf8
  locale-coding-system: utf-8-unix

Major mode: Eshell

Minor modes in effect:
  shell-dirtrack-mode: t
  eshell-prompt-mode: t
  eshell-hist-mode: t
  eshell-pred-mode: t
  eshell-cmpl-mode: t
  eshell-proc-mode: t
  eshell-arg-mode: t
  tooltip-mode: t
  global-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 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 electric uniquify ediff-hook
vc-hooks lisp-float-type mwheel term/pgtk-win pgtk-win term/common-win
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 xwidget-internal dbusbind inotify dynamic-setting
system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit
pgtk multi-tty make-network-process native-compile emacs)

Memory information:
((conses 16 94111 7609)
 (symbols 48 8410 0)
 (strings 32 25538 2114)
 (string-bytes 1 947094)
 (vectors 16 18049)
 (vector-slots 8 364818 9944)
 (floats 8 26 27)
 (intervals 56 233 0)
 (buffers 992 11))