Re: Extending define-derived-mode

[Yuan Fu <casouri@gmail.com>]

> On May 31, 2023, at 11:39 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Stefan Monnier <monnier@iro.umontreal.ca>
>> Cc: Eli Zaretskii <eliz@gnu.org>,  emacs-devel@gnu.org,
>>  mickey@masteringemacs.org,  theo@thornhill.no,  dgutov@yandex.ru
>> Date: Thu, 01 Jun 2023 00:06:54 -0400
>> 
>>> Keep in mind that when people try out tree-sitter modes, they are unlikely
>>> to just throw away their config for the old mode; also since tree-sitter and
>>> grammars aren’t the easiest to install, people working on multiple machines
>>> probably want both tree-sitter and no-tree-sitter modes configured and ready
>>> to go. So I think we’ll see a lot of people having config for both modes (me
>>> included).
>> 
>> Good point.
> 
> It's a good point, indeed, but with some mode pairs is very hard
> (read: impossible) to achieve.  A notable example is c-mode and
> c-ts-mode: the former has a lot of mode-specific commands and features
> that cannot be used with the latter, because there's no equivalent
> infrastructure that supports the same interfaces, and sometimes
> because the feature makes no sense in a TS-based mode.  We try very
> hard to use the same key bindings and variable names where it does
> make sense, but the group of features where that is possible is very
> small.  For example, all the enormous set of features we have in CC
> mode around indentation and its customization cannot be "ported" to
> c-ts-mode and c++-ts-mode, because the latter is built on completely
> different analysis of the text.  Another example is the ad-hoc support
> for some frequently-use macro names that CC mode has.

I fully agree. Note thought that I wasn’t saying ts and non-ts modes should accept the same set of configs. I know all-too-well that’s impossible (for the majority of modes). I was saying that sometimes there are configs that can be shared (enabling electric-quote-local-mode, for example), and it would be nice to put them in a single hook rather than duplicating the code in two hooks. 

Yuan