Re: Tree-sitter and major mode inheritance

[Eli Zaretskii]

> From: Yuan Fu <casouri@gmail.com>
> Date: Sun, 20 Nov 2022 01:19:13 -0800
> Cc: Dmitry Gutov <dgutov@yandex.ru>,
>  emacs-devel@gnu.org,
>  monnier@iro.umontreal.ca,
>  theo@thornhill.no
> 
> 
> 
> > On Nov 19, 2022, at 11:11 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> > 
> >> Date: Sun, 20 Nov 2022 00:03:35 +0200
> >> Cc: Eli Zaretskii <eliz@gnu.org>, emacs-devel@gnu.org,
> >> monnier@iro.umontreal.ca, theo@thornhill.no
> >> From: Dmitry Gutov <dgutov@yandex.ru>
> >> 
> >> On 19.11.2022 23:49, Yuan Fu wrote:
> >>> Actually, that’s evidence supporting his preference: js-mode will remain 
> >>> to be the native implementation, so inheriting from it is exactly as 
> >>> before. Js-ts-mode will install tree-sitter stuff. And js-base-mode 
> >>> wouldn’t do much.
> >> 
> >> But js-base-mode will be used in auto-mode-alist?
> > 
> > NO!!!  auto-mode-alist should keep using js-mode, as it does today.
> > 
> > js-base-mode, if we need it, should just be a vehicle for easy sharing of
> > common stuff between several modes that pertain to the same or similar
> > languages.  It should NOT be visible to users, so should not appear in any
> > variables users are likely to customize.
> 
> Alright, changing js-mode to ja-native-mode is indeed a bad idea. So this is 
> what I did: for eg, js-mode, I created js-ts-mode and js-base-mode. Js-mode 
> and js-ts-mode inherits js-base-mode. Auto-mode-alist has javascript-mode 
> (that’s what’s in the list right now, I didn’t change it).
> 
> If a user wants to use tree-sitter for javascript, they can add 
> (javascript-mode . js-ts-mode) into major-mode-remap-alist.

Or manually turn on js-ts-mode.  Or customize auto-mode-alist to have
js-ts-mode be used in preference to js-mode.  Right?

> If someone wants js-mode and js-ts-mode to share the same configuration, he 
> needs to configure js-base-mode. So js-base-mode isn’t completely invisible. 

We should not advertise js-base-mode.  If people want to share
configurations between two modes, they should do that explicitly via their
own hook function, or via copying the configurations.  (And some of the
configurations cannot be shared anyway, because the two modes use different
features for font-lock and indentation.)