From 5afb04b62e0bbfa9fcb963c7dacb9e419d3b4f38 Mon Sep 17 00:00:00 2001
From: Adam Gastineau <adam@agg.im>
Date: Thu, 30 Jan 2025 09:20:43 -0800
Subject: [PATCH] fix(ui): add proper CORS header for loading traces in HMR
 mode (#34558)

---
 .../playwright-core/src/server/trace/viewer/traceViewer.ts    | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/packages/playwright-core/src/server/trace/viewer/traceViewer.ts b/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
index f852f6c996..55cbca1cad 100644
--- a/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
+++ b/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
@@ -67,6 +67,10 @@ export async function startTraceViewerServer(options?: TraceViewerServerOptions)
   server.routePrefix('/trace', (request, response) => {
     const url = new URL('http://localhost' + request.url!);
     const relativePath = url.pathname.slice('/trace'.length);
+    if (process.env.PW_HMR) {
+      // When running in Vite HMR mode, port is hardcoded in build.js
+      response.appendHeader('Access-Control-Allow-Origin', 'http://localhost:44223');
+    }
     if (relativePath.endsWith('/stall.js'))
       return true;
     if (relativePath.startsWith('/file')) {