Re: c-ts-mode

[João Távora]

On Fri, Sep 8, 2023 at 12:26 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: João Távora <joaotavora@gmail.com>
> > Cc: Theodor Thornhill <theo@thornhill.no>,  casouri@gmail.com,
> >   spacibba@aol.com,  emacs-devel@gnu.org
> > Date: Fri, 08 Sep 2023 08:25:50 +0100
> >
> > > What I had in mind was a simple alist, like CC Mode uses, with an
> > > infrastructure function to install it.  Patches are welcome.
> >
> > It would certainly work for me, at least for my very simple case, and I
> > would be happy for this.  Not sure it is half as powerful, for example
> > how would you make that simple alist express cases where you want to add
> > the rules _after_ the base set?
>
> How does CC Mode support this (if it does)?

No idea, I don't know CC Mode's styling interface well beyond
the trivial example I showed.

It does seems like CC Mode have different mechanics?
Maybe order doesn't matter there?

> Anything beyond that is, of course, welcome, but it is
> less important from my POV.

Sure makes sense.  As I said I'm just conjecturing someone
will need that flexibility because rule ordering is a fundamental
part of the mechanics in TS and I don't think we abstract it
away.  But personally, for those ridiculous two rules, I didn't
need it at all, adding at the front was just fine

Anyway, it's worth pointing out that unless you're extremely adept
at crafting indentation styles for Emacs, you're always in a losing
battle when working on multiple projects, since many projects
nowadays (not just C/C++) use an external format definition.
A .clang-format  (even we have one since 2017) or other similar
files.  These are understood by other editors and tools.

Maybe in the past CC Mode's styles were very useful, but I don't
think they attract the same interest today because there are these
external tools.  For the same reason, I don't predict ts
indentation styles to become widely used.

Of course, this is a big annoyance, because there always multiple
competing sources of indentation rules.  Emacs TAB use one thing,
everyone else uses something else.

Personally I've not been fighting this, i.e. I gave up.  I use
Emacs indentation rules to more or less align the file with the rules
and then make sure to run the tool (maybe via eglot-format)
before committing.  It'd be great if I could rely on indent-region
or C-M-q to produce the canonical indentation like I do in
Lisp modes, but I can't.

A more promising solution to this whole problem would be
to somehow bring these external formatter's rules to meet Emacs's
idea of "just indent these lines".

I tried to do that with Eglot (and Theo helped out) via
indent-region-function but we alas it didn't work very well,
because -- at least for clangd -- the LSP formatter (which
delegates to clang-format under the hood) has a tendency to add
and remove newlines even if you ask it to stay within the
same line.  So basic things like indenting an empty line is
essentially impossible.

João