bug#19877: 24.4; highlight-regexp displays nonsense options for faces

[Boruch Baum]

WHAT HAPPENS:
=============

The documentation for `highlight-regexp' ( info:emacs#Highlight
Interactively]] ) says, "While being prompted for a face use ‘M-n’ and
‘M-p’ to cycle through them." However, repeatedly keying ‘M-n’ will
toggle through the entries in `hi-lock-face-defaults' *twice*, and then
will start displaying _other items_, presumably from some other
 history ring, but not necessarily faces. In my case, some of the _other
items_ that appear when I ‘M-n’ cycle, were: apropos-variable-button,
org-target, bookmark-menu-bookmark, org-agenda-date-today, and
ido-incomplete-regexp.


Furthermore, if one of those _other items_ is selected,
`highlight-regexp' exits, without indicating an error, and without
highlighting the requested regexp in *any* face.


Furthermore, `highlight-regexp', as an alias for function
`hi-lock-face-buffer', hard codes face `hi-yellow' as a default, but
that default isn't used when one of those non-face _other items_ are
selected.


Finally, it seems inconsistent with the emacs spirit of flexibility to
have `hi-yellow' be hard-coded as a default in function
`hi-lock-face-buffer'.


Post-finally, courtesy of the indentation police: in function
`hi-lock-read-face-name', the `then` and `else` elements of the
function's only `if` form, are out-dented.


WHAT I EXPECTED:
================
1] There are a few ways I expected `M-n` could toggle - either through
only the entries in `hi-lock-face-defaults'; through the entries in
`hi-lock-face-defaults' plus faces the user had previously entered for
hi-lock purposes; or through the entries in `hi-lock-face-defaults' plus
faces the user had previously entered for any purpose. It should never
*offer* the user an invalid option. Also, it should never accept an
entry that isn't a face.

2] If, somehow, something other than a valid face is entered, the user
should be notified, and sent back to the prompt, with the same option of
`M-n` cycling.

3] If, somehow, something other than a valid face is accepted, the
default should be used.

4] The default should not be hard-coded as `hi-yellow`, or as anything
else. It should be set to user-definable variable, say
`hi-lock-default-face', which could have a default value of `hi-yellow'.

5] Indentation readability / inconsistency quibble.



PARTIAL SOLUTION
================
1] Why `M-n` cycled twice through legitimate defaults before offering up
garbage.

For the following, paste function `hi-lock-read-face-name' into a
scratch buffer in order to follow my line number references


The value of `defaults',  when `hi-lock-interactive-patterns' is *nil*,
because of line 7, hi-lock--unused-faces = hi-lock-face-defaults
because of line 9, last-used-face = nil
so at line 12,
         (defaults (append hi-lock-face-defaults
                           (cdr (member nil hi-lock-face-defaults))
                           hi-lock-face-defaults))
which simplifies to
         (defaults (append hi-lock-face-defaults
                           nil
                           hi-lock-face-defaults))

OTOH, when `hi-lock-interactive-patterns' is not *nil*,
because of line 7, hi-lock--unused-faces = nil
so at line 12,
         (defaults
           (append nil
                   (cdr (member last-used-face hi-lock-face-defaults))
                   hi-lock-face-defaults))


CONSEQUENTLY, line 12 should be
         (defaults
           (if hi-lock-interactive-patterns
             (let ((index (position last-used-face hi-lock-face-defaults)))
               (append (last       hi-lock-face-defaults (1+ index))
                       (butlast    hi-lock-face-defaults (1+ index))))
            hi-lock-face-defaults))


2] on the issue of the strange entries in the history, I've only traced
the lisp code as far as `read-from-minibuffer' in minibuf.c




In GNU Emacs 24.4.1 (x86_64-pc-linux-gnu)
 of 2014-12-09 on gaia, modified by Debian
System Description:     Debian 7.0 GNU/Linux wheezy/testing

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/s\
ite-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/s\
ite-lisp
 --with-x=no --without-gconf --without-gsettings '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.utf8
  locale-coding-system: utf-8-unix

Major mode: IBuffer

Minor modes in effect:
  highlight-current-line-minor-mode: t
  desktop-save-mode: t
  savehist-mode: t
  winner-mode: t
  global-hi-lock-mode: t
  hi-lock-mode: t
  delete-selection-mode: t
  shell-dirtrack-mode: t
  tooltip-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
  buffer-read-only: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

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Features:
(shadow sort mail-extr emacsbug message rfc822 mml mml-sec mm-decode
mm-bodies mm-encode mailabbrev ...)

Memory information:
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