On Wed, Mar 29, 2023, 6:29 PM João Távora <joaotavora@gmail.com> wrote:

> On Wed, Mar 29, 2023 at 3:26 AM Eli Zaretskii <eliz@gnu.org> wrote:
> >
> > > From: João Távora <joaotavora@gmail.com>
> > > Cc: Dmitry Gutov <dgutov@yandex.ru>,  dancol@dancol.org,
> casouri@gmail.com,
> > >   emacs-devel@gnu.org, theo@thornhill.no
> > > Date: Tue, 28 Mar 2023 23:11:05 +0100
> > >
> > > Though a number of indenting problems would remain after that, at least
> > > this one clear annoyance would be solved.  So if there are no
> > > objections, I propose to apply this patch.
> > >
> > > diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
> > > index 59eb9fc23e6..88360716381 100644
> > > --- a/lisp/progmodes/c-ts-mode.el
> > > +++ b/lisp/progmodes/c-ts-mode.el
> > > @@ -956,10 +956,6 @@ c-ts-base-mode
> > >    ;; Comment
> > >    (c-ts-common-comment-setup)
> > >
> > > -  ;; Electric
> > > -  (setq-local electric-indent-chars
> > > -              (append "{}():;,#" electric-indent-chars))
> > > -
> > >    ;; Imenu.
> > >    (setq-local treesit-simple-imenu-settings
> > >                (let ((pred #'c-ts-mode--defun-valid-p))
> > >
> > > In master?  In emacs-29?
> >
> > I suggest to do this in emacs-29, but conditionally, with a
> > defcustom.  This will allow users to try both ways and maybe we will
> > have some feedback regarding what is the best way.
>
> I'm not fond of creating a defcustom to work around what I consider
> as a simple bug and to configure something which the user can already
> configure with a two-line mode hook addition. So I won't do that
> change myself.
>
> > I'm also interested to know what other editors do, as Daniel points
> > out.
>
> I don't use many other editors but I can tell you that online editors
> like the ones found at hackerrank.com, which I strongly suspect are
> based on LSP + treesitter behave as if electric-pair-mode was on
> and electric-indent-chars is just '(?\n).  I.e. they auto-indent
> on newline and don't bounce around when symbols such as ':',')' or
> ';' are typed.  As far as I can tell, auto-indenting on characters
> other than newline is an Emacs invention that only works well if a
> mode has near-perfect predictive powers of indentation, which
> c++-ts-mode clearly doesn't have (yet).
>
> And then my personal opinion is that it is an annoying
> feature to have on by default as it whole lines about.
> Having electric-indent-chars set to '(?\n), like c++-mode
> has, is fine.
>

I would think the advantage of using tree-sitter is triggering formatting
based on lexemes and grammar symbols rather than raw characters.  So
instead of ';' a formatting action might be triggered by the parser
deducing a lexeme/symbol STATEMENT-SEPARATOR, as opposed to a ';'
separating clauses in a for statement.

Lynn