How can i test changes to a grammar file with GitHub's highlighter?

[AmjadHD]

Recent changes to the Nim grammar broke syntax highlighting in GitHub although it works well in Sublime Text.
Following AI suggestions, I created this test repo hoping that linguist would pickup the override, but it didn't work.
What am I doing wrong?

[lildude]

In short, you can't test grammar changes directly against GitHub's syntax highlighter.

The syntax highlighter is an internal project independent of Linguist and it reads the grammar files from the linguist-grammars.tar.gz tarball that is attached to each release. This file is produced by the grammar compiler. If you extract it, you can see the JSON it produces for your grammar.

The best way to test your grammars is against TextMate which will get you very close. Also make sure you use PCRE-compatible regexes in your grammar.

If you fork this repo and then update the grammar by replacing it with itself, the grammar compiler will re-run and you can see the result in the linguist-grammars directory.

Other things you might find useful include #6756 and the discussion in #7255

[AmjadHD]

I suspect this regex to match identifiers including unicode is the culprit:

[A-Za-z\x80-\x{10FFFF}&&[^∙∘×★⊗⊘⊙⊛⊠⊡∩∧⊓±⊕⊖⊞⊟∪∨⊔]]

What's wrong with it?

[RedCMD]

Use \x{80} for Shiki

nim-lang/NimLime@e5014fd