Function requestHandlerImpl

packages/next/src/server/lib/router-server.ts:226–722

(req, res)

    require('./render-server') as typeof import('./render-server')

  const requestHandlerImpl: WorkerRequestHandler = async (req, res) => {
    addRequestMeta(req, 'relativeProjectDir', relativeProjectDir)

    // internal headers should not be honored by the request handler
    if (!process.env.NEXT_PRIVATE_TEST_HEADERS) {
      filterInternalHeaders(req.headers)
    }

    if (
      !opts.minimalMode &&
      config.i18n &&
      config.i18n.localeDetection !== false
    ) {
      const urlParts = (req.url || '').split('?', 1)
      let urlNoQuery = urlParts[0] || ''

      if (config.basePath) {
        urlNoQuery = removePathPrefix(urlNoQuery, config.basePath)
      }

      const pathnameInfo = getNextPathnameInfo(urlNoQuery, {
        nextConfig: config,
      })

      const domainLocale = detectDomainLocale(
        config.i18n.domains,
        getHostname({ hostname: urlNoQuery }, req.headers)
      )

      const defaultLocale =
        domainLocale?.defaultLocale || config.i18n.defaultLocale

      const { getLocaleRedirect } =
        require('../../shared/lib/i18n/get-locale-redirect') as typeof import('../../shared/lib/i18n/get-locale-redirect')

      const parsedUrl = parseUrlUtil((req.url || '')?.replace(/^\/+/, '/'))

      const redirect = getLocaleRedirect({
        defaultLocale,
        domainLocale,
        headers: req.headers,
        nextConfig: config,
        pathLocale: pathnameInfo.locale,
        urlParsed: {
          ...parsedUrl,
          pathname: pathnameInfo.locale
            ? `/${pathnameInfo.locale}${urlNoQuery}`
            : urlNoQuery,
        },
      })

      if (redirect) {
        res.setHeader('Location', redirect)
        res.statusCode = RedirectStatusCode.TemporaryRedirect
        res.end(redirect)
        return
      }
    }