Hacky support for treesit in Emacs core

[ymarco]

CC @casouri

I wanted to use tree-sitter-langs packaged grammars and queries with treesit in Emacs core.

I'm not expecting these bunch of hacks to be accepted, it's more of a talking
point on compatibility/collaboration between elisp-tree-sitter and treesit.

Points:

• elisp-tree-sitter maps capture name X to face tree-sitter-hl-face:X, while
  treesit expects X to be a face by itself. I tried to replace X with
  tree-sitter-hl-face:X, but seems like colons end identifier names in
  tree-sitter's query language. What I ended up doing is replacing X with the
  parent face of tree-sitter-hl-face:X
• .match? and .eq? predicates in elisp-tree-sitter are renamed to #match and #euqal
  in treesit, and #match has its arguments swapped in relation to .match?
• treesit expects grammars to be files in the format libtree-sitter-X, so it
  can't find tree-sitter-lang's grammars, so I symlinked each grammar file with
  itself prefixed with libtree-sitter-.

[jsmestad]

@ymarco question: does the treesit integration in core support multi-language documents?

[ymarco]

I haven't delved much into that, it would be doable with functions like treesit-set-ranges in the API. Yuan wrote a texinfo node about it in the feature/tree-sitter branch (see Parsing Text in Multiple Languages and treesit-parser-set-included-ranges), but I think it'd be better to ask him on emacs-devel what an actual mode using these would look like.

[ymarco]

@kiennq I just saw your fork on reddit, what does it do? I couldn't make sense of the commit history...

[kiennq]

@ymarco My fork is similar to your commit with additional to:

• doesn't take dependencies on emacs-tree-sitter, the only dependency is the builtin treesit. The recipe for it is (treesit-langs :repo "kiennq/tree-sitter-langs" :fetcher github :files ("tree-sitter-langs-build.el" "treesit-*.el" "queries"))
• Add some more parsers with their highlight queries (taken from the parser's repo or neovim's tree-sitter repo)