Function devRouter

packages/cli/src/util/dev/router.ts:50–293

(
  reqUrl: string = '/',
  reqMethod?: string,
  routes?: Route[],
  devServer?: DevServer,
  vercelConfig?: VercelConfig,
  previousHeaders?: HttpHeadersConfig,
  missRoutes?: Route[],
  phase?: HandleValue | null
)

}

export async function devRouter(
  reqUrl: string = '/',
  reqMethod?: string,
  routes?: Route[],
  devServer?: DevServer,
  vercelConfig?: VercelConfig,
  previousHeaders?: HttpHeadersConfig,
  missRoutes?: Route[],
  phase?: HandleValue | null
): Promise<RouteResult> {
  let result: RouteResult | undefined;
  let { pathname: reqPathname, search: reqSearch } = url.parse(reqUrl);
  reqPathname = reqPathname || '/';
  const reqQuery = parseQueryString(reqSearch);
  const combinedHeaders: HttpHeadersConfig = { ...previousHeaders };
  let status: number | undefined;
  let isContinue = false;

  const requestTransforms: Transform[] = [];
  let responseTransforms: Transform[] | undefined;

  // Try route match
  if (routes) {
    let idx = -1;
    for (const routeConfig of routes) {
      idx++;
      isContinue = false;

      if (isHandler(routeConfig)) {
        // We don't expect any Handle, only Source routes
        continue;
      }

      const { src, headers, methods } = routeConfig;

      if (Array.isArray(methods) && reqMethod && !methods.includes(reqMethod)) {
        continue;
      }

      const keys: string[] = [];
      const flags = devServer && devServer.isCaseSensitive() ? '' : 'i';
      const matcher = PCRE(`%${src}%${flags}`, keys);
      const match =
        matcher.exec(reqPathname) || matcher.exec(reqPathname.substring(1));

      if (match) {
        const routeTransforms = routeConfig.transforms
          ? resolveTransforms(routeConfig.transforms, {
              match,
              keys,
              env: devServer?.envConfigs.runEnv,
            })
          : [];

        // A `service` destination is a terminal marker-only handoff, no
        // transforms will be applied for this route
        const isServiceMarker =
          typeof routeConfig.destination === 'object' &&