Yes, works like charm.

sob., 21 cze 2025 o 16:44 Eli Zaretskii <eliz@gnu.org> napisał(a):

> [Please use Reply All to reply, to keep the bug tracker CC'ed.]
>
> > From: Jacek Świerk <jacekswierk@gmail.com>
> > Date: Sat, 21 Jun 2025 16:29:19 +0200
> >
> > Here's more detailed reproduction recipe:
> >
> > 1. Define a custom indentation style for C++:
> > (defun my--c++-ts-mode-indent-style ()
> >   "Use BSD style but don't indent inside namespaces."
> >   `((cpp
> >      ((n-p-gp nil nil "namespace_definition") grand-parent 0)
> >      ,@(cdr (car (c-ts-mode--simple-indent-rules 'cpp 'bsd))))))
> >
> > 2. Set the custom style as default:
> > (setopt c-ts-mode-indent-style 'my--c++-ts-mode-indent-style)
> >
> > 3. Enable C++ treesit mode:
> > (c++-ts-mode)
> >
> > 4. Verify `treesit-simple-indent-rules` - it shows only `((cpp))`
> instead of the expected rules.
> >
> > This happens because c-ts-mode--simple-indent-rules, which is called
> while
> > changing major mode (line 1563) to c++-ts-mode, has pcase only for 4
> styles
> > (gnu, k&r, linux and bsd), meaning it doesn't handle the situation when
> > c-ts-mode-indent-style is set to some custom function. I can work around
> it by
> > calling (setopt c-ts-mode-indent-style 'my--c++-ts-mode-indent-style)
> after
> > switching to c++-ts-mode with a hook but is this the expected flow?
>
> Thanks.  Does the patch below fix the problem?
>
> diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
> index 0df9fe3..5155193 100644
> --- a/lisp/progmodes/c-ts-mode.el
> +++ b/lisp/progmodes/c-ts-mode.el
> @@ -1487,8 +1487,10 @@ c-ts-mode
>        (setq-local comment-end " */")
>        ;; Indent.
>        (setq-local treesit-simple-indent-rules
> -                  (c-ts-mode--simple-indent-rules
> -                   'c c-ts-mode-indent-style))
> +                  (if (functionp c-ts-mode-indent-style)
> +                      (funcall c-ts-mode-indent-style)
> +                    (c-ts-mode--simple-indent-rules
> +                     'c c-ts-mode-indent-style)))
>        ;; (setq-local treesit-simple-indent-rules
>        ;;             `((c . ,(alist-get 'gnu (c-ts-mode--indent-styles
> 'c)))))
>        ;; Font-lock.
> @@ -1560,8 +1562,10 @@ c++-ts-mode
>
>        ;; Indent.
>        (setq-local treesit-simple-indent-rules
> -                  (c-ts-mode--simple-indent-rules
> -                   'cpp c-ts-mode-indent-style))
> +                  (if (functionp c-ts-mode-indent-style)
> +                      (funcall c-ts-mode-indent-style)
> +                    (c-ts-mode--simple-indent-rules
> +                     'cpp c-ts-mode-indent-style)))
>
>        ;; Font-lock.
>        (setq-local treesit-font-lock-settings
>