feat: show warning on 431 response

packages/vite/src/node/http.ts

@@ -6,6 +6,7 @@ import type {
 } from 'node:http'
 import type { ServerOptions as HttpsServerOptions } from 'node:https'
 import type { Connect } from 'types/connect'
+import colors from 'picocolors'
 import { isObject } from './utils'
 import type { ProxyOptions } from './server/middlewares/proxy'
 import type { Logger } from './logger'
@@ -183,3 +184,27 @@ export async function httpServerStart(
     })
   })
 }
+
+export function setClientErrorHandler(
+  server: HttpServer,
+  logger: Logger
+): void {
+  server.on('clientError', (err, socket) => {
+    if ((err as any).code === 'HPE_HEADER_OVERFLOW') {
+      if (!socket.writableEnded) {
+        socket.end(
+          'HTTP/1.1 431 Request Header Fields Too Large\r\n\r\n' +
+            'Request Header was too large. Node.js limits request header size. ' +
+            'Use https://nodejs.org/api/cli.html#--max-http-header-sizesize to change max header size.'
+        )
+      }
+      logger.warn(
+        colors.yellow(
+          'Server / WS server responded with "431 Request Header Fields Too Large." ' +
+            'Node.js limits request header size and the request was dropped. ' +
+            'Use https://nodejs.org/api/cli.html#--max-http-header-sizesize to change max header size.'
+        )
+      )
+    }
+  })
+}

packages/vite/src/node/preview.ts

@@ -6,7 +6,12 @@ import type { Connect } from 'types/connect'
 import corsMiddleware from 'cors'
 import type { ResolvedServerOptions, ResolvedServerUrls } from './server'
 import type { CommonServerOptions } from './http'
-import { httpServerStart, resolveHttpServer, resolveHttpsConfig } from './http'
+import {
+  httpServerStart,
+  resolveHttpServer,
+  resolveHttpsConfig,
+  setClientErrorHandler
+} from './http'
 import { openBrowser } from './server/openBrowser'
 import compression from './server/middlewares/compression'
 import { proxyMiddleware } from './server/middlewares/proxy'
@@ -78,6 +83,7 @@ export async function preview(
     app,
     await resolveHttpsConfig(config.preview?.https, config.cacheDir)
   )
+  setClientErrorHandler(httpServer, config.logger)
 
   // apply server hooks from plugins
   const postHooks: ((() => void) | void)[] = []

packages/vite/src/node/server/index.ts

@@ -12,7 +12,12 @@ import type { Connect } from 'types/connect'
 import launchEditorMiddleware from 'launch-editor-middleware'
 import type { SourceMap } from 'rollup'
 import type { CommonServerOptions } from '../http'
-import { httpServerStart, resolveHttpServer, resolveHttpsConfig } from '../http'
+import {
+  httpServerStart,
+  resolveHttpServer,
+  resolveHttpsConfig,
+  setClientErrorHandler
+} from '../http'
 import type { InlineConfig, ResolvedConfig } from '../config'
 import { isDepsOptimizerEnabled, resolveConfig } from '../config'
 import {
@@ -301,6 +306,10 @@ export async function createServer(
     : await resolveHttpServer(serverConfig, middlewares, httpsOptions)
   const ws = createWebSocketServer(httpServer, config, httpsOptions)
 
+  if (httpServer) {
+    setClientErrorHandler(httpServer, config.logger)
+  }
+
   const { ignored = [], ...watchOptions } = serverConfig.watch || {}
   const watcher = chokidar.watch(path.resolve(root), {
     ignored: [