bug#68246: 30.0.50; Add non-TS mode as extra parent of TS modes

[Eli Zaretskii]

> From: João Távora <joaotavora@gmail.com>
> Date: Mon, 8 Jan 2024 00:12:50 +0000
> Cc: monnier@iro.umontreal.ca, casouri@gmail.com, 68246@debbugs.gnu.org
> 
> On Sun, Jan 7, 2024 at 6:55 AM Eli Zaretskii <eliz@gnu.org> wrote:
> 
> > But that is not necessarily true in all cases.
> 
> I specifically said I was speaking for 2 packages I created,
> Eglot and Yasnippet, and possibly for lsp-mode how is facing the same
> problem, which is answering the question:
> 
>   what, if any, is the language/file type for a given major mode?
> 
> I can't speak to those other cases unless someone bring them forth.

A generalization should be based on as many use cases as possible.

> > Also, some major modes don't have a "language" attribute, in
> > the usual sense of that word.
> 
> Then I guess "nil" would be a fine default for anything not inheriting from
> "prog-mode"?

That's not useful, since, for example, TS and non-TS mods for those
"no-language" modes will still want to be treated the same in some
situations, like .dir-locals.el.

> > IOW, this is IMO an even more leaky abstraction than what we get with
> > derived-mode-add-parents.
> 
> We don't seem to share the same concept of what a "leaky abstraction" is.
> In my world, it's an abstraction that exposes details of the thing
> it's supposed to abstract away.

That's the sense in which I'm using it.

> Unless we're trying to abstract away lisp symbols, I don't see how
> set/get-language-for-mode is leaky.

It attempts to abstract a trait that isn't abstract, by going in the
opposite direction of that used for abstractions.

> But if Stefan's patch is supposed to also abstract away the
> language-mode correspondence

It isn't, AFAIU.