css/postcss.config.cjs

const autoprefixer = require('autoprefixer')
const sass = require('@csstools/postcss-sass')
const scss = require('postcss-scss')
const scssImport = require('postcss-import')
const { join } = require('path')
const path = require('path')
const fs = require('fs')

module.exports = {
  map: {
    sourcesContent: false,
    annotation: true
  },
  customSyntax: scss,
  parser: scss,
  plugins: [
    scssImport,
    sass({
      includePaths: [join(__dirname, 'node_modules')],
      outputStyle: process.env.CSS_MINIFY === '0' ? 'expanded' : 'compressed'
    }),
    autoprefixer,
    require('postcss-custom-properties-fallback')({
      importFrom: [
        () => {
          const primitiveFallbacks = [
            'color-fallbacks.json',
            'base/size/size.json',
            'base/typography/typography.json',
            'functional/size/border.json',
            'functional/size/breakpoints.json',
            'functional/size/size-coarse.json',
            'functional/size/size-fine.json',
            'functional/size/size.json',
            'functional/size/viewport.json',
            'functional/typography/typography.json',
          ]
          let customProperties = {}
          for (const filePath of primitiveFallbacks) {
            const fileData = fs.readFileSync(path.join(__dirname, './node_modules/@primer/primitives/tokens-next-private/fallbacks/', filePath), 'utf8')
            customProperties = {...customProperties, ...JSON.parse(fileData)}
          }

          return { customProperties: customProperties };
        }
      ]
    }),
  ]
}