Re: Questions about tree-sitter

["Augustin Chéneau (BTuin)" <btuin@mailo.com>]

Le 30/08/2023 à 09:03, Yuan Fu a écrit :
> 
> 
>> On Aug 29, 2023, at 2:26 PM, Augustin Chéneau (BTuin) <btuin@mailo.com> wrote:
>>
>> Hello,
>>
>> I have a few questions about tree-sitter.
>>
>> I'm currently developing a grammar for GNU Bison alongside a tree-sitter
>> major mode, it's a work in progress.  The grammar is here:
>> <https://gitlab.com/btuin2/tree-sitter-bison>, still incomplete but so
>> far able to parse simple files, and the major mode prototype is
>> attached to this message.
>>
>> So, the questions:
>>
>> 1. Is there a way to reload a grammar?
>>
>> Emacs is pretty nice as a playground for testing grammars, but once a
>> grammar is loaded, it won't be loaded again until Emacs restarts (as far
>> as I know).
>> Is it possible to reload a grammar after modifying it?
> 
> No, and it’s probably not easy to implement either, since unloading the grammar would require Emacs to purge/invalid all the node/query/parsers using that grammar.
> 
>> 2. How to mix multiple languages?
>>
>> It would be very useful for Bison since its mixed with C or other languages.
>> According to the documentation I need to use the function
>> `treesit-range-rules` to set the variable `treesit-range-settings`, but
>> it seems to have no effect.  The language in the selected nodes doesn't
>> change (as attested by `(treesit-language-at (point))`).
>>
>> I did it that way (extracted from the attachment):
>>
>> (setq-local treesit-range-settings
>>       (treesit-range-rules
>>        :embed 'c
>>        :host 'bison
>>        '((undelimited_code_block) @capture)))
>>
>> Am I missing something?
> 
> The ranges are set correctly, actually. But the C parse sees all those blocks stitched together as a whole, rather than individual blocks, and the code it sees is obviously not syntactically correct.
> 
> We should really work on supporting isolated ranges, there has been multiple requests for it. I’ll try to work on that.
> 
>> 3. Is it possible to trigger a hook when a node is modified?
>>
>> Since Bison supports multiple languages (C, C++, Java and D), I'd like
>> to watch the declaration "%language LANGUAGE" to change the embedded
>> language when needed.
>> Is there a way to do that?
> 
> treesit-parser-add-notifier might be what you want.
> 
> Yuan
> 

I see.  Thank you for your answers and for your great work on tree-sitter!