Function compileCSS

packages/vite/src/node/plugins/css.ts:1429–1504

(
  environment: PartialEnvironment,
  id: string,
  code: string,
  workerController: PreprocessorWorkerController,
  urlResolver?: CssUrlResolver,
)

}

async function compileCSS(
  environment: PartialEnvironment,
  id: string,
  code: string,
  workerController: PreprocessorWorkerController,
  urlResolver?: CssUrlResolver,
): Promise<{
  code: string
  map?: SourceMapInput
  modules?: Record<string, string>
  deps?: Set<string>
}> {
  const { config } = environment
  const lang = CSS_LANGS_RE.exec(id)?.[1] as CssLang | undefined
  const deps = new Set<string>()

  // pre-processors: sass etc.
  let preprocessorMap: ExistingRawSourceMap | { mappings: '' } | undefined
  if (isPreProcessor(lang)) {
    const preprocessorResult = await compileCSSPreprocessors(
      environment,
      id,
      lang,
      code,
      workerController,
    )
    code = preprocessorResult.code
    preprocessorMap = preprocessorResult.map
    preprocessorResult.deps?.forEach((dep) => deps.add(dep))
  } else if (lang === 'sss' && config.css.transformer === 'lightningcss') {
    const sssResult = await transformSugarSS(environment, id, code)
    code = sssResult.code
    preprocessorMap = sssResult.map
  }

  const transformResult = await (config.css.transformer === 'lightningcss'
    ? compileLightningCSS(
        environment,
        id,
        code,
        deps,
        workerController,
        urlResolver,
      )
    : compilePostCSS(
        environment,
        id,
        code,
        deps,
        lang,
        workerController,
        urlResolver,
      ))

  if (!transformResult) {
    return {
      code,
      map: config.css.devSourcemap ? preprocessorMap : { mappings: '' },