bug#18928: 24.4; viper-save-setting produces invalid configuration file

[Keshav Kini]

Steps to reproduce:

1) Run `emacs -Q`.
2) Execute the following elisp in the scratch buffer:

(require 'viper-util)
(setq x 3)
(viper-save-setting 'x nil "/tmp/.viper")
(setq x 4)
(viper-save-setting 'x nil "/tmp/.viper")

Expected result:

/tmp/.viper should contain "(setq x '4)"

Actual result:

/tmp/.viper contains "(setq x  '4 '3)"


The above is a minimized example.  An actual user behavior that
demonstrates the bug is as follows.

1)  Run `emacs -Q`.
2)  Do `M-x viper-mode RET'.
3)  You are queried with "Inhibit Viper startup message? (y or n) ".
    Answer 'n'.
4)  After a few seconds, you are asked to "please specify your level of
    familiarity with the venomous VI Peril (and the VI Plan for Emacs
    Rescue)" and told that you can "change it at any time by typing `M-x
    viper-set-expert-level RET'".  Answer '3'.
5)  You are asked whether you "wish to make this change permanent".
    Answer 'y'.
6)  As suggested, do `M-x viper-set-expert-level RET'.
7)  Answer '4'.
8)  Answer 'y'.
9)  Close emacs.
10) Run `emacs -Q`.
11) Do `M-x viper-mode RET`.

The following error appears in the minibuffer:

Wrong type argument: symbolp, (quote 3)


Suggested fix:

Modify the regular expression at line 652 of
lisp/emulation/viper-util.el to correctly recognize variable values such
as "'3".  Or, perhaps make viper utilize the standard customize
functionality built into recent versions of Emacs, rather than rolling
its own configuration file writer and parser.


Thanks,
    Keshav


In GNU Emacs 24.4.1 (x86_64-pc-linux-gnu, GTK+ Version 3.14.3)
 of 2014-10-25 on trouble, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.11601000
System Description:     Debian GNU/Linux unstable (sid)

Configured using:
 `configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.4/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.4/site-lisp:/usr/share/emacs/site-lisp
 --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
 --libexecdir=/usr/lib --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.4/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.4/site-lisp:/usr/share/emacs/site-lisp
 --with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars
 'CFLAGS=-g -O2 -fstack-protector-strong -Wformat
 -Werror=format-security -Wall' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-z,relro'

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-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
  transient-mark-mode: t

Recent input:
M-x r e p o r t - e m a c s - b u g <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util help-fns mail-prsvr mail-utils time-date tooltip electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list newcomment lisp-mode
prog-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
minibuffer 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 make-network-process
dbusbind gfilenotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 71506 9282)
 (symbols 48 17750 0)
 (miscs 40 39 113)
 (strings 32 9118 4274)
 (string-bytes 1 249719)
 (vectors 16 9006)
 (vector-slots 8 388591 12854)
 (floats 8 63 81)
 (intervals 56 213 8)
 (buffers 960 11)
 (heap 1024 41537 888))