Yup, so this should say Textmate-like grammars, not “TextMate grammars”

MicroLighter uses the CSS Custom Highlight API and TextMate grammars

The grammars look like they are forks of upstream, eliminating all the Oniguruma constructs and so forth:

https://github.com/davatron5000/microlighter/tree/main/src/grammars

To be fair the README does address this, which I missed the first time. But the tagline is not accurate

MicroLighter reads TextMate grammars with the browser’s native RegExp … It does not use Oniguruma, WebAssembly, or generated token markup.

But it also munges regexes with regexes, which is pretty gross:

/**
 * Replace TextMate end-pattern backreferences with escaped begin captures.
  ...
 */
const expandEnd = (pattern, beginMatch) => pattern.replace(/\\(\d+)/g, (reference, index) => {
  return beginMatch[index] === undefined ? reference : escapeRegex(beginMatch[index]);
});

So yeah it seems poorly-specified – not something I’d want to build on. TextMate itself is a bit poorly specified, which is why everyone has to drag along Oniguruma

I would like something like this, but not confined to JavaScript regexes. I am thinking about a “lexing VM” for syntax highlighting and other tools like sloccount, that’s built on top of regular languages and constructs like “find constant string”, “capture delimiter”, etc. I’ve been thinking about that since using writing syntax highlighters in Vim and C++/re2c: https://github.com/oils-for-unix/oils.vim/blob/main/doc/algorithms.md

score 1 · canonical