Re: Tree-sitter central configuration variable

[Yuan Fu]

> On Nov 28, 2024, at 11:12 PM, Eshel Yaron <me@eshelyaron.com> wrote:
> 
> Hi,
> 
> Yuan Fu <casouri@gmail.com> writes:
> 
>> Actually, I want to expand this to something that allows users to
>> configure tree-sitter modes and toggle on/off tree-sitter features.
>> 
> [...]
>> 
>> What do you guys think about something like this:
>> 
>> (setq treesit-global-configuration
>>      '((c-ts-mode
>>         ;; Set treesit-font-lock-level to 4
>>         (font-lock-level . 4)
> [...]
>>         )))
>> 
> 
> FWIW, I think tree-sitter should be treated as an implementation detail,
> not a user-facing concept.  Tree-sitter empowers major mode developers,
> but users shouldn't have to know or care about tree-sitter to benefit
> from it.  So a TS-specific configuration user option is not the best
> approach IMO.  (For the same reason, I'm not a big fan of the "powered
> by tree-sitter" that we have today in the docstring of various modes.)

I principle, I agree, and that’s what we’ve been doing: we expose tree-sitter 
as a mechanism for major modes to build on. However, the reality is, something 
like this just aren’t going to be transparent—users know it’s powered by 
tree-sitter, they’ll need to have tree-sitter knowledge for non-trivial 
customizations (eg, add a font-lock rule or indent rule), and the major mode is 
tied-in with tree-sitter, implementing the major mode with another parser 
library would require creating a new major mode.

Once you accept that these modes are tied with tree-sitter, a TS-specific 
configuration starts to seem pretty reasonable. Also, think of the advantage of 
using a single set of configuration: no need to read the manual and learn the 
variables etc for each individual major modes; as long as the mode uses 
tree-sitter features, you learn the configuration framework once and use it on 
every mode.

> Instead, when it comes to settings that apply across major modes, I
> think we should focus on knobs that make sense whether or not a mode is
> TS-based, and have the TS-based modes respect such universal settings.

Perhaps you mean something that configures things like font-lock, imenu, etc? 
(I can’t really think of a third example). That’s a bit ambitious, the return 
is unclear to me, and gods bless whoever wants to fight through emacs-devel for 
it :-) OTOH, a tree-sitter configuration variable is pretty concrete, I know 
people want it, and more or less noncontroversial (I hope).

Yuan