fix: serve 4xx pages when using dev server (#225)

Author: anthonychu

src/msha/middlewares/request.middleware.ts

@@ -93,22 +93,25 @@ function serveStaticOrProxyReponse(req: http.IncomingMessage, res: http.ServerRe
   }
 
   const customUrl = isCustomUrl(req);
+  logger.silly(`customUrl: ${chalk.yellow(customUrl)}`);
   if (req.url?.includes("index.html") || customUrl) {
-    // serve index.htmn or custom pages from user's `outputLocation`
+    // serve index.html or custom pages from user's `outputLocation`
 
     logger.silly(`custom page or index.html detected`);
     // extract user custom page filename
     req.url = req.url?.replace(DEFAULT_CONFIG.customUrlScheme!, "");
     target = SWA_CLI_OUTPUT_LOCATION;
 
-    logger.silly(` - isCustomUrl: ${chalk.yellow(customUrl)}`);
     logger.silly(` - url: ${chalk.yellow(req.url)}`);
     logger.silly(` - statusCode: ${chalk.yellow(res.statusCode)}`);
     logger.silly(` - target: ${chalk.yellow(target)}`);
   }
 
+  const is4xx = res.statusCode >= 400 && res.statusCode < 500;
+  logger.silly(`is4xx: ${is4xx}`);
+
   // if the static app is served by a dev server, forward all requests to it.
-  if (IS_APP_DEV_SERVER()) {
+  if (IS_APP_DEV_SERVER() && (!is4xx || customUrl)) {
     logger.silly(`remote dev server detected. Proxying request`);
     logger.silly(` - url: ${chalk.yellow(req.url)}`);
     logger.silly(` - code: ${chalk.yellow(res.statusCode)}`);