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

[Dmitry Gutov]

On 06/01/2024 05:19, Yuan Fu wrote:

> The good thing about derived-mode-add-parents is that it doesn’t need major 
> mode author’s cooperation. Even a normal user can do it themselves.

True.

> Then there is the problem Eli pointed out, base-mode hooks runs before child 
> major mode body does. It’s probably fine for most of the things, but if you 
> want to change some buffer local variable that the major mode sets, base-mode 
> hook can’t help. (Arguable a niche use-case, but my point is base-mode hooks 
> have their limits.)

This is the same for all other case of mode inheritance (e.g. js2-mode 
inheriting from js-mode, or python-ts-mode inheriting from python-mode).

It would be odd if some inheriters would have this inconvenience, and 
others not.

> Obviously derived-mode-add-parents can’t help with hooks. But adding the config 
> to two hooks doesn’t seem to be too bad. Plus I haven’t come up with good 
> solution. So I’m not too eager to solve that inconvenience.

I was thinking some "proper" language registry is the way to go. Like a 
custom structure tracking the correspondence between file names and 
languages, and a separate association list for lang->major-mode.

But it would require more changes indeed.

> As for adding xxx-mode to xxx-ts-mode’s parent, I think it’s fine? Like others 
> in the thread, I couldn’t think of a scenarios where this will be problematic. 
> I thought about adding xxx-lang as the parent of both xxx-mode and xxx-ts-mode, 
> but that’s probably not very helpful, since the goal is to make things work for 
> ts-mode without needing to change the existing code, and using xxx-lang still 
> requires modifying existing code.

OTOH, the required changes could be made fairly minimal (aside those in 
the user's config): add a new keyword to define-derived-mode which would 
add (run-hooks 'xyz-lang-hook) at the end.