fix(directives): theme() breaks @apply

[Dunqing]

fix: #1021

[netlify]

✅ Deploy Preview for unocss canceled.

Built without sensitive environment variables

Name	Link
🔨 Latest commit	654e380
🔍 Latest deploy log	https://app.netlify.com/sites/unocss/deploys/62938ae56f6d0a0008651643

[Dunqing]

css-tree cannot parse Function in css variables, so theme() does not work.

Do we need to support it?

@antfu cc

[hannoeru]

@Dunqing you can get raw data then throw it back to css-tree parser to parse that part as Function.

[antfu]

We could just do a simple regex replace instead of relying on the parse result.

[ameinhardt]

also, there's parseCustomProperty

const ast = parse(originalCode || code.original, {
  parseAtrulePrelude: false,
  positions: true,
  parseCustomProperty: true,
  filename,
})

Wouldn't that work?