From d2f02a848bb2b4f8da0102f00988954d193de59d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=BF=A0=20/=20green?= <green@sapphi.red>
Date: Mon, 18 Jul 2022 03:45:27 +0900
Subject: [PATCH] fix: return 500 on proxy error only if possible (fixes #9172)
 (#9175)

---
 packages/vite/src/node/server/middlewares/proxy.ts | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/packages/vite/src/node/server/middlewares/proxy.ts b/packages/vite/src/node/server/middlewares/proxy.ts
index 78095080157b4e..0f83ecb723fa19 100644
--- a/packages/vite/src/node/server/middlewares/proxy.ts
+++ b/packages/vite/src/node/server/middlewares/proxy.ts
@@ -55,11 +55,13 @@ export function proxyMiddleware(
             error: err
           }
         )
-        res
-          .writeHead(500, {
-            'Content-Type': 'text/plain'
-          })
-          .end()
+        if (!res.writableEnded) {
+          res
+            .writeHead(500, {
+              'Content-Type': 'text/plain'
+            })
+            .end()
+        }
       } else {
         config.logger.error(`${colors.red(`ws proxy error:`)}\n${err.stack}`, {
           timestamp: true,