Re: Status update of tree-sitter features

[Mickey Petersen <mickey@fyeah.org>]

Yuan Fu <casouri@gmail.com> writes:

> Hi,
>
> As the complete feature freeze approaching, this is probably the last set of features added to Emacs 29. I stuffed  them in just in time ;-)
>
> 1. There is a new predicate in the query language, #pred. It’s like #equal and #match. Basically it allows you to filter the captured node with an arbitrary function. Right now there are some queries in the font-lock settings that matches a little more than what we actually want. For example, for the property feature, we only want the “bb” in “aa.bb”, but not in “aa.bb(cc)”, because the latter is a method, not property. The query usually matches both. With this new predicate we can use a function to filter out the methods.
>
> If we can ensure that every query only captures the intended nodes, the font-lock queries can be reused for context extraction: using the query for the variable feature, I can find all the variables in a given region, etc.
>

Looks useful. But this, I think, goes back to the issue I raised with you in an email: that queries are recursive, as each query is (I pressume this is how it is done in tree-sitter) applied to each node in the tree. That makes it very hard to build a query that pattern matches against nested nodes only once. It is very hard, when you have recursive queries with self-similar matches, to filter out recursed matches. Particularly when you are writing generic code that merely acts on the output of arbitrary queries.

#pred is surely no different to applying `seq-filter' or similar to the query result, no?