Highlighting that seems ignored in CM6

Just had this, the resolution for me was that i had codemirror@6 and @codemirror/basic-setup@0.20.0 installed at the same time, removing @codemirror/basic-setup@0.20.0 fixed it

FWIW, I ran into this same issue and the fix for me was disabling dependency injection in my vite.config.js for the @lezer/highlight package.

optimizeDeps: {
    exclude: [