From 836ddfae19bae765893275e631167b301587d194 Mon Sep 17 00:00:00 2001
From: Hiroshi Ogawa <hi.ogawa.zz@gmail.com>
Date: Tue, 6 Oct 2026 15:13:29 +0900
Subject: [PATCH] test(ui): fix playwright trace source locations (#11508)

Co-authored-by: Hiroshi Ogawa <4232207+hi-ogawa@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
---
 test/ui/test/helper.ts | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/test/ui/test/helper.ts b/test/ui/test/helper.ts
index 8f283b773..e09aa8ffb 100644
--- a/test/ui/test/helper.ts
+++ b/test/ui/test/helper.ts
@@ -9,10 +9,25 @@ import { expect } from '@playwright/test'
 import { preview } from 'vite'
 import { startVitest } from 'vitest/node'
 
+// Vitest's main-process module runner (globalSetup, reporters, etc.) replaces
+// Error.prepareStackTrace on startup, which breaks Playwright's source-mapped
+// locations of test steps in traces. Restoring it only loses source maps for
+// errors from those main-process modules, which these tests don't rely on.
+async function preserveStackTrace<T>(fn: () => Promise<T>): Promise<T> {
+  const prepareStackTrace = Error.prepareStackTrace
+  try {
+    return await fn()
+  } finally {
+    Error.prepareStackTrace = prepareStackTrace
+  }
+}
+
 export async function startVitestSimple(cliOptions: CliOptions): Promise<Vitest> {
   const stdout = new Writable({ write: (_, __, callback) => callback() })
   const stderr = new Writable({ write: (_, __, callback) => callback() })
-  const vitest = await startVitest(undefined, cliOptions, {}, { stdout, stderr })
+  const vitest = await preserveStackTrace(() =>
+    startVitest(undefined, cliOptions, {}, { stdout, stderr }),
+  )
   await vitest.close()
   return vitest
 }
@@ -24,7 +39,9 @@ export async function startVitestUi(
   // silence Vitest logs
   const stdout = new Writable({ write: (_, __, callback) => callback() })
   const stderr = new Writable({ write: (_, __, callback) => callback() })
-  const vitest = await startVitest(undefined, cliOptions, viteOverrides, { stdout, stderr })
+  const vitest = await preserveStackTrace(() =>
+    startVitest(undefined, cliOptions, viteOverrides, { stdout, stderr }),
+  )
 
   const address = vitest.vite.httpServer?.address()
   assert(address && typeof address === 'object', 'Invalid server address')
@@ -44,7 +61,7 @@ export async function startHtmlReportPreview(
 ): Promise<{ previewServer: PreviewServer; url: string }> {
   const stdout = new Writable({ write: (_, __, callback) => callback() })
   const stderr = new Writable({ write: (_, __, callback) => callback() })
-  await startVitest('test', undefined, cliOptions, {}, { stdout, stderr })
+  await preserveStackTrace(() => startVitest('test', undefined, cliOptions, {}, { stdout, stderr }))
 
   const previewServer = await preview(previewOptions)
   const address = previewServer.httpServer?.address()
-- 
2.51.2