bug#75456: 31.0.50; Cannot find the definition of the predicate in `treesit-thing-settings'" sexp-list)

[Yuan Fu <casouri@gmail.com>]

> On Jan 9, 2025, at 2:42 PM, Vincenzo Pupillo <v.pupillo@gmail.com> wrote:
> 
> Ciao Juri,
> 
> In data giovedì 9 gennaio 2025 19:10:28 Ora standard dell’Europa centrale, 
> Juri Linkov ha scritto:
>>> Ciao,
>>> this problem occurs with js-ts-mode when jsdoc is enabled. Occurs when you
>>> place the cursor in a comment highlighted by jsdoc.
>>> This is the error message:
>>> 
>>> "treesit-show-paren-data--categorize: peculiar error: ("Cannot find the
>>> definition of the predicate in `treesit-thing-settings'" sexp-list)"
>> 
>> Recently I fixed bug#75198 and tested it on your mhtml-ts-mode
>> where it works nicely, and (treesit-language-at (point))
>> returns e.g. 'css' on embedded css.
>> 
>> However, now I discovered that (treesit-language-at (point))
>> returns 'javascript' on embedded jsdoc parts of a js file.
>> 
>> I wonder is this intended?
>> 
>> Since 'treesit-node-match-p' uses node's parser, I could use
>> (treesit-parser-language (treesit-node-parser (treesit-node-at (point))))
>> that returns 'jsdoc'.
>> 
>> But first I'd like to know why treesit-language-at doesn't return the same?
> 
> Local parsers, like jsdoc or phpdoc, are "ignored" by several functions used 
> by treesit. But I don't know in detail how treesit works.
> I tried to return local parser languages ​​in the past, but both indentation 
> and font-locking got messed up.
> I just tried and the result is the same (maybe I did something wrong), and 
> then treesit-parser-list also returns jsdoc as if it were a global parser.
> 
> @Yuan can be of more help.
> 
> Thanks.
> 
> Vincenzo

If local parsers somehow doesn’t work, it’s a bug. What are the functions that ignore local parsers? And how exactly does indentation and font-lock mess up?

For indentation, there’s a special condition: if the largest node at point is a root node for the local parser, we don’t use it for matching indent rules, because it’s impossible to figure out how to indent it; instead, Emacs uses the host parser’s node at that point. (The logic is in treesit--indent-largest-node-at).

What do you mean by  treesit-parser-list also returns jsdoc as if it were a global parser? Does it return the jsdoc parser even you pass nil to the TAG parameter? If so, I think it’s because some treesit function accidentally created it when looking for a parser for jsdoc. I’ll try fix that.

Yuan