bug#38067: Command Popup Hangs Emacsclient During Startup

[Gustaf Waldemarson <gustaf.waldemarson@gmail.com>]

Hello,

I've run into a slightly annoying issue with the emacsclient hanging
during startup due to it being unable to display a command prompt. To
recreate the behavior:

1. create a file with the contents (e.g., init.el):

,----
 (defun my-hang-client ()
   "This is a test function."
   (condition-case nil
       (let* ((choices (list
                       "This function seems to hang Emacsclient."))
              (result (completing-read "This is a hang test:" choices nil t))
              (index (cl-position choices :test 'equal))))
     ('quit)))

 (add-hook 'c-mode-hook      #'my-hang-client)
 (add-hook 'c++-mode-hook    #'my-hang-client)
`----

1. Start a new Emacs server: `emacs --load init.el -Q --daemon=hangtest'

2. Open a new C/C++ file from the terminal (doesn't need to exist):
   `emacsclient -nc -s hangtest main.cpp'

Truth be told I'm not sure if this is the intended behavior or not, but
I personally find it a bit annoying to have the client hang on me when
I'm not opening the files in the right way. Interestingly, cancelling the
command with C-c and executing it again opens the window normally,
but without issuing the command prompt.

(Also, If it is actually intended behavior, is there an idiomatic way to
rewrite the hook such that it will still be called during startup, but
prevent the hanging?)



In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
 of 2019-11-05 built on E105888
Repository revision: 91c732f687a61ba130acf38d5142bec6369ebd68
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Ubuntu 16.04.6 LTS

Recent messages:
Starting Emacs daemon.
Back to top level
Making completion list...
delete-backward-char: Text is read-only [24 times]

Configured using:
 'configure --prefix=/home/guswal01/.local
 '--program-transform-name=s/^ctags$/ctags.emacs/''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND DBUS GSETTINGS GLIB NOTIFY INOTIFY
GNUTLS LIBXML2 FREETYPE HARFBUZZ XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11
XDBE XIM MODULES THREADS PDUMPER LCMS2 GMP

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

Major mode: C++//l

Minor modes in effect:
  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
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
format-spec rfc822 mml mml-sec password-cache epa derived epg epg-config
gnus-util rmail rmail-loaddefs text-property-search time-date subr-x 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 cc-mode cc-fonts
easymenu cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars
cc-defs cl-loaddefs cl-lib server 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 timer
select scroll-bar mouse jit-lock font-lock syntax facemenu 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 loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 16 68540 8695)
 (symbols 48 8557 1)
 (strings 32 22083 1694)
 (string-bytes 1 831101)
 (vectors 16 12975)
 (vector-slots 8 167883 5844)
 (floats 8 25 40)
 (intervals 56 384 0)
 (buffers 1000 14)
 (heap 1024 13969 1032))