Re: tree-sitter user rules.

[Ergus]

Hi Yuan:

On January 28, 2025 2:51:00 AM GMT+01:00, Yuan Fu <casouri@gmail.com> wrote:
>
>
>> On Jan 17, 2025, at 10:52 AM, Ergus <spacibba@aol.com> wrote:
>> 
>> Hi:
>> 
>> I have been hacking a bit treesitter to add a few custom indentation
>> rules that behave "weird" in my system.
>> 
>> At the end I have this workaround, but I am wondering if we could add
>> something less hacky in order to allow the user insert some rules over
>> existing styles:
>> 
>> ```
>> (defun my/treesit-simple-indent (oldfun node parent bol)
>>    "Allow indent with custom rules without hacks in the predefined rules
>> 
>> It is possible to change the treesit-indent-function BUT the python mode
>> breaks because there is some hacky condition assigning the indentation
>> function in the tree-sitter library."
>>    (or (when-let* ((rules (alist-get (treesit-node-language parent)
>>      my/treesit-indent-rules))
>>    (treesit-simple-indent-rules my/treesit-indent-rules)
>>    (result (funcall oldfun node parent bol))
>>    ((or (car result)
>> (cdr result))))
>>  result)
>> (funcall oldfun node parent bol)))
>> 
>>  ;; Add an advise to check my indentations before the default ones.
>>  ;; I cannot use another function and set it to treesit-indent-function
>>  ;; because some code in tressitter.el apparently checks that
>>  ;; (eq treesit-indent-function '#treesit-simple-indent)
>>  (advice-add 'treesit-simple-indent :around #'my/treesit-simple-indent)
>> 
>>  ;; The for example for rust:
>>  (defun my/rust-ts-mode-hook ()
>>    "Hook to improve indentation in rust mode"
>>    (setq-local tab-width 4)
>> 
>>    (setq-local my/treesit-indent-rules
>> `((rust . (((and (parent-is "function_item")
>> (node-is "block")) parent-bol 0))))))
>>  (add-hook 'rust-ts-mode-hook #'my/rust-ts-mode-hook)
>> 
>> ```
>> 
>> I propose to add a variable equivalent to my/treesit-indent-rules and
>> make treesit-simple-indent try to get a match from there before, else
>> rely on treesit-simple-indent-rules
>> 
>> WDYT?
>
>Hey Ergus, have you considered this:
>
>(setq-local treesit-simple-indent-rules
>           `((rust . ,(append (your rules)
>                           (alist-get ‘rust treesit-simple-indent-rules)))))
>
>In the major mode hook? That’s the way of customization I had in mind when 
>writing the indentation facility.

Yes I actually use that until now. But it becomes cumbersome in some cases like 
when working with different projects and I need to add different rules in the 
dir_locals file for each of them.

>I do agree that we can have a function to simplify it. Similar to 
>treesit-add-font-lock-rules, we can add a treesit-add-simple-indent-rules, 
>that also hands adding rules before/after the existing rules, or a certain 
>rule.
>
>Yuan

A variable will be simpler to manage and keep clean the original rules. 
Separated for user custom ones.

Using functions for this is more complex compared with setting a custom 
variable. And won't take advantages of the defcustom facility. But that's just 
my opinion ;)

Best,
Ergus