提供静态资源服务的中间件（针对 publicDir 里面的文件）

    1. function servePublicMiddleware(dir: string): Connect.NextHandleFunction {
    2.   // 通过 sirv 创建 public 的静态资源服务中间件
    3.   const serve = sirv(dir, sirvOptions)
    5.   return (req, res, next) => {
    6.     // 如果是通过 import 获取资源，则直接跳过
    7.     if (isImportRequest(req.url!)) {
    8.       return next()
    9.     }
    10.     // 如果不是 import 则尝试在 publicDir 中获取静态资源，如果获取不到依旧会去下个中间件处理
    11.     serve(req, res, next)
    12.   }
    13. }
    15. // sirv 配置
    16. const sirvOptions: Options = {
    17.   dev: true,
    18.   etag: true,
    19.   extensions: [],
    20.   setHeaders(res, pathname) {
    21.     // Matches js, jsx, ts, tsx.
    22.     // The reason this is done, is that the .ts file extension is reserved
    23.     // for the MIME type video/mp2t. In almost all cases, we can expect
    24.     // these files to be TypeScript files, and for Vite to serve them with
    25.     // this Content-Type.
    26.     if (/\.[tj]sx?$/.test(pathname)) {
    27.       res.setHeader('Content-Type', 'application/javascript')
    28.     }
    29.   }
    30. }
    32. // import 的请求蒲培
    33. const importQueryRE = /(\?|&)import(?:&|$)/
    34. isImportRequest = (url: string): boolean => importQueryRE.test(url)