bug#72156: 31.0.50; defcustom set issue

bug#72156: 31.0.50; defcustom set issue

[Ergus via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Hi:

I have this defcustom:

```
(defcustom gtags-mode-features '(control meta)
  "HELLO WORLD"
  :type '(set (const control)
              (const meta)
              (const shift)
              (const hyper)
              (const super)
              (const alt)))
```

When I try the customize-variable I get this:

```
Hide Gtags Mode Features:
Set:
[X] control
[X] meta
[ ] shift
[ ] hyper
[ ] super
[ ] alt
   [ State ]: EDITED, shown value does not take effect until you set or save it.
   HELLO WORLD
Groups: [Gtags Mode]
```

But, if I do the next change and save


```
Hide Gtags Mode Features:
Set:
[X] control
[X] meta
[X] shift
[ ] hyper
[ ] super
[ ] alt
   [ State ]: EDITED, shown value does not take effect until you set or save it.
   HELLO WORLD
Groups: [Gtags Mode]
```

The customize variable value saved is:

'(gtags-mode-features3 '(shift))

it only saved the "new" value and ignores the previous
existing ones.

When I restart and check the variable's value I get as expected '(shift)
and lost the control and meta.

Going to customize-variable again I get:

```
Hide Gtags Mode Features:
Set:
[ ] control
[ ] meta
[X] shift
[ ] hyper
[ ] super
[ ] alt
   [ State ]: EDITED, shown value does not take effect until you set or save it.
   HELLO WORLD
Groups: [Gtags Mode]
```

Consistent with the variable value, but inconsistent with what was
actually saved before.

IF instead of selecting a new value I un-select some, then variable
saves nil and will be nil.





In GNU Emacs 31.0.50 (build 13, x86_64-pc-linux-gnu, GTK+ Version
 3.24.43, cairo version 1.18.0) of 2024-07-17 built on RTX
Repository revision: 438a7da5530a32d20de769e3450e4fc3a74e9236
Repository branch: project
System Description: Arch Linux

Configured using:
 'configure --prefix=/home/ergo/.local/ --with-mailutils --with-pgtk
 --with-modules --with-cairo --with-harfbuzz
 --with-native-compilation=aot
 '--program-transform-name=s/^ctags$/ctags.emacs/''

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
LCMS2 LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PGTK
PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS
TREE_SITTER WEBP XIM GTK3 ZLIB

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

Major mode: Custom

Minor modes in effect:
  fancy-compilation-mode: t
  global-auto-revert-mode: t
  diff-hl-margin-mode: t
  corfu-terminal-mode: t
  global-corfu-mode: t
  corfu-mode: t
  project-multi-mode: t
  gtags-mode: t
  repeat-mode: t
  xterm-mouse-mode: t
  xclip-mode: t
  override-global-mode: t
  winner-mode: t
  save-place-mode: t
  delete-selection-mode: t
  savehist-mode: t
  global-display-fill-column-indicator-mode: t
  display-fill-column-indicator-mode: t
  global-display-line-numbers-mode: t
  display-line-numbers-mode: t
  which-key-mode: t
  show-paren-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  context-menu-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  minibuffer-regexp-mode: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
/mnt/casa/gits/emacs_clones/cuda-mode/cuda-mode hides /home/ergo/.config/emacs/elpa/cuda-mode-20240716.1936/cuda-mode
/mnt/casa/gits/emacs_clones/gtags-mode/gtags-mode hides /home/ergo/.config/emacs/elpa/gtags-mode-1.8/gtags-mode
/home/ergo/.config/emacs/elpa/transient-20240713.2102/transient hides /home/ergo/.local/share/emacs/31.0.50/lisp/transient

Features:
(shadow sort fancy-compilation compile comint ansi-osc ansi-color
comp-run comp-common mail-extr emacsbug message mailcap yank-media puny
rfc822 mml mml-sec epa derived epg rfc6068 epg-config gnus-util
text-property-search 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 tabify help-fns radix-tree
cus-edit pp cus-start cus-load wid-edit find-func autorevert filenotify
ffap thingatpt url-parse auth-source eieio eieio-core icons
password-cache json map url-vars vc-git elec-pair whitespace
flyspell-correct flyspell ispell completion-preview diff-hl-margin
diff-hl-dired citre-lang-fileref citre-tags citre-ctags citre-readtags
citre-readtags-tables citre-backend-interface citre-common-tag rx
citre-common-util dired-x dired dired-loaddefs diff-hl log-view
pcvs-util vc-dir ewoc vc vc-dispatcher diff-mode track-changes
corfu-terminal popon corfu project-multi-mode gtags-mode cl-macs subr-x
files-x xref project term/tmux term/xterm xterm init repeat cape compat
use-package-ensure use-package-diminish xt-mouse xclip edmacro kmacro
byte-opt gv use-package-bind-key bind-key cl-extra help-mode
simple-16-theme winner ring saveplace delsel savehist easy-mmode
display-fill-column-indicator display-line-numbers diminish which-key
cl-seq use-package-core cl-loaddefs cl-lib bytecomp byte-compile
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julia-ts-mode-autoloads julia-mode-autoloads languagetool-autoloads
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git-commit-autoloads magit-section-autoloads markdown-mode-autoloads
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notmuch-autoloads objed-autoloads opencl-mode-autoloads
paradox-autoloads phi-search-autoloads pkg-info-autoloads epl-autoloads
pkgbuild-mode-autoloads platformio-mode-autoloads async-autoloads
popon-autoloads popup-autoloads projectile-autoloads
projection-autoloads protobuf-mode-autoloads protobuf-ts-mode-autoloads
ptemplate-templates-autoloads ptemplate-autoloads scopeline-autoloads
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sudo-edit-autoloads systemd-autoloads tmux-mode-autoloads
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bug#72156: 31.0.50; defcustom set issue

[Eli Zaretskii]

> Date: Wed, 17 Jul 2024 14:08:59 +0200
> From:  Ergus via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> I have this defcustom:
> 
> ```
> (defcustom gtags-mode-features '(control meta)
>   "HELLO WORLD"
>   :type '(set (const control)
>               (const meta)
>               (const shift)
>               (const hyper)
>               (const super)
>               (const alt)))
> ```
> 
> When I try the customize-variable I get this:
> 
> ```
> Hide Gtags Mode Features:
> Set:
> [X] control
> [X] meta
> [ ] shift
> [ ] hyper
> [ ] super
> [ ] alt
>    [ State ]: EDITED, shown value does not take effect until you set or save it.
>    HELLO WORLD
> Groups: [Gtags Mode]
> ```
> 
> But, if I do the next change and save
> 
> 
> ```
> Hide Gtags Mode Features:
> Set:
> [X] control
> [X] meta
> [X] shift
> [ ] hyper
> [ ] super
> [ ] alt
>    [ State ]: EDITED, shown value does not take effect until you set or save it.
>    HELLO WORLD
> Groups: [Gtags Mode]
> ```
> 
> The customize variable value saved is:
> 
> '(gtags-mode-features3 '(shift))
> 
> it only saved the "new" value and ignores the previous
> existing ones.
> 
> When I restart and check the variable's value I get as expected '(shift)
> and lost the control and meta.
> 
> Going to customize-variable again I get:
> 
> ```
> Hide Gtags Mode Features:
> Set:
> [ ] control
> [ ] meta
> [X] shift
> [ ] hyper
> [ ] super
> [ ] alt
>    [ State ]: EDITED, shown value does not take effect until you set or save it.
>    HELLO WORLD
> Groups: [Gtags Mode]
> ```
> 
> Consistent with the variable value, but inconsistent with what was
> actually saved before.
> 
> IF instead of selecting a new value I un-select some, then variable
> saves nil and will be nil.

This seems to be some bug in handling the 'set' type of defcustoms.  I
see the same problem when customizing completions-merging-modes from
completion.el.  Perhaps Mauro (CC'ed) could chime in and suggest how
to solve this.

bug#72156: 31.0.50; defcustom set issue

[Eli Zaretskii]

merge 72156 72404
thanks

> Cc: 72156@debbugs.gnu.org
> Date: Sat, 20 Jul 2024 11:50:47 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > Date: Wed, 17 Jul 2024 14:08:59 +0200
> > From:  Ergus via "Bug reports for GNU Emacs,
> >  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> > 
> > I have this defcustom:
> > 
> > ```
> > (defcustom gtags-mode-features '(control meta)
> >   "HELLO WORLD"
> >   :type '(set (const control)
> >               (const meta)
> >               (const shift)
> >               (const hyper)
> >               (const super)
> >               (const alt)))
> > ```
> > 
> > When I try the customize-variable I get this:
> > 
> > ```
> > Hide Gtags Mode Features:
> > Set:
> > [X] control
> > [X] meta
> > [ ] shift
> > [ ] hyper
> > [ ] super
> > [ ] alt
> >    [ State ]: EDITED, shown value does not take effect until you set or save it.
> >    HELLO WORLD
> > Groups: [Gtags Mode]
> > ```
> > 
> > But, if I do the next change and save
> > 
> > 
> > ```
> > Hide Gtags Mode Features:
> > Set:
> > [X] control
> > [X] meta
> > [X] shift
> > [ ] hyper
> > [ ] super
> > [ ] alt
> >    [ State ]: EDITED, shown value does not take effect until you set or save it.
> >    HELLO WORLD
> > Groups: [Gtags Mode]
> > ```
> > 
> > The customize variable value saved is:
> > 
> > '(gtags-mode-features3 '(shift))
> > 
> > it only saved the "new" value and ignores the previous
> > existing ones.
> > 
> > When I restart and check the variable's value I get as expected '(shift)
> > and lost the control and meta.
> > 
> > Going to customize-variable again I get:
> > 
> > ```
> > Hide Gtags Mode Features:
> > Set:
> > [ ] control
> > [ ] meta
> > [X] shift
> > [ ] hyper
> > [ ] super
> > [ ] alt
> >    [ State ]: EDITED, shown value does not take effect until you set or save it.
> >    HELLO WORLD
> > Groups: [Gtags Mode]
> > ```
> > 
> > Consistent with the variable value, but inconsistent with what was
> > actually saved before.
> > 
> > IF instead of selecting a new value I un-select some, then variable
> > saves nil and will be nil.
> 
> This seems to be some bug in handling the 'set' type of defcustoms.  I
> see the same problem when customizing completions-merging-modes from
> completion.el.  Perhaps Mauro (CC'ed) could chime in and suggest how
> to solve this.

This actually seems to be the same problem as bug#72404, since the fix
proposed by Stephen there fixes this one as well.  So I'm merging them.