From edc5b1193e7d5ef883f85b488e24cafe0f624551 Mon Sep 17 00:00:00 2001
From: Valeriia Radchenko <valeriia.radchenko.dev@gmail.com>
Date: Mon, 9 Nov 2026 12:56:10 -0700
Subject: [PATCH] test: wait for HMR fixture readiness after navigation

---
 playground/hmr/__tests__/hmr.spec.ts          | 42 ++++++++++++++++---
 .../hmr-no-partial-accept.spec.ts             |  7 ++--
 playground/hmr/vite.config.ts                 | 27 ++++++++++++
 playground/test-utils.ts                      | 11 -----
 4 files changed, 68 insertions(+), 19 deletions(-)

diff --git a/playground/hmr/__tests__/hmr.spec.ts b/playground/hmr/__tests__/hmr.spec.ts
index d4313e1d3e77ba..09e3f389bd0c3c 100644
--- a/playground/hmr/__tests__/hmr.spec.ts
+++ b/playground/hmr/__tests__/hmr.spec.ts
@@ -10,7 +10,6 @@ import {
   editFile,
   getBg,
   getColor,
-  gotoLatestBuild,
   hotUpdatedLog,
   isBuild,
   isBundledDev,
@@ -524,8 +523,10 @@ if (!isBuild) {
     const CONNECTED = /connected/
 
     const baseDir = 'accept-exports'
-    const openPage = (testDir: string) =>
-      gotoLatestBuild(`${viteTestUrl}/${testDir}/`)
+    const openPage = async (testDir: string) => {
+      await page.goto(`${viteTestUrl}/${testDir}/`, { waitUntil: 'commit' })
+      await page.waitForSelector('html[data-hmr-ready="true"]')
+    }
 
     describe('when all used exports are accepted', () => {
       const testDir = baseDir + '/main-accepted'
@@ -1144,7 +1145,10 @@ if (!isBuild) {
             "export { value as childValue } from './child'",
           ),
         )
-      }, 'file-delete-restore/child.js hot data after prune: undefined')
+      }, [
+        'file-delete-restore/child.js hot data after prune: undefined',
+        hotUpdatedLog(parentFile),
+      ])
       await expect
         .poll(() => page.textContent('.file-delete-restore'))
         .toMatch('parent:child')
@@ -1352,7 +1356,35 @@ if (!isBuild) {
   )
 
   test('import.meta.hot?.accept', async () => {
-    await gotoLatestBuild(viteTestUrl)
+    if (isBundledDev) {
+      // Navigation can finish before the new HMR client registers.
+      let delayRegistration = true
+      await page.routeWebSocket('**', (socket) => {
+        const server = socket.connectToServer()
+        const queuedMessages: (string | Buffer)[] = []
+        let queueMessages = false
+        socket.onMessage((message) => {
+          if (
+            delayRegistration &&
+            String(message).includes('vite:client-connected')
+          ) {
+            delayRegistration = false
+            queueMessages = true
+            setTimeout(() => {
+              for (const queued of queuedMessages) server.send(queued)
+              queueMessages = false
+            }, 500)
+          }
+          if (queueMessages) {
+            queuedMessages.push(message)
+          } else {
+            server.send(message)
+          }
+        })
+      })
+    }
+    await page.goto(viteTestUrl)
+    await page.waitForSelector('html[data-hmr-ready="true"]')
 
     const el = page.locator('.optional-chaining')
     await untilBrowserLogAfter(
diff --git a/playground/hmr/__tests__/no-partial-accept/hmr-no-partial-accept.spec.ts b/playground/hmr/__tests__/no-partial-accept/hmr-no-partial-accept.spec.ts
index 5f242bff704e03..7aeb3c09d276e0 100644
--- a/playground/hmr/__tests__/no-partial-accept/hmr-no-partial-accept.spec.ts
+++ b/playground/hmr/__tests__/no-partial-accept/hmr-no-partial-accept.spec.ts
@@ -1,7 +1,6 @@
 import { beforeAll, describe, expect, it } from 'vitest'
 import {
   editFile,
-  gotoLatestBuild,
   hotUpdatedLog,
   isBuild,
   page,
@@ -11,8 +10,10 @@ import {
 
 describe.runIf(!isBuild)('acceptExports with hmrPartialAccept off', () => {
   const CONNECTED = /connected/
-  const openPage = (testDir: string) =>
-    gotoLatestBuild(`${viteTestUrl}/${testDir}/`)
+  const openPage = async (testDir: string) => {
+    await page.goto(`${viteTestUrl}/${testDir}/`, { waitUntil: 'commit' })
+    await page.waitForSelector('html[data-hmr-ready="true"]')
+  }
 
   describe('importer that uses only accepted exports', () => {
     const testDir = 'accept-exports/main-accepted'
diff --git a/playground/hmr/vite.config.ts b/playground/hmr/vite.config.ts
index ccf615f0b10b51..131f7fc2be4619 100644
--- a/playground/hmr/vite.config.ts
+++ b/playground/hmr/vite.config.ts
@@ -61,6 +61,33 @@ export default defineConfig(({ command }) => ({
     },
   },
   plugins: [
+    // A round trip settles fallback reloads and client registration before edits.
+    {
+      name: 'test-hmr-ready',
+      apply: 'serve',
+      configureServer(server) {
+        server.environments.client.hot.on('test:ready', (_data, client) => {
+          client.send('test:ready')
+        })
+      },
+      transformIndexHtml: {
+        order: 'pre',
+        handler() {
+          return [
+            {
+              tag: 'script',
+              attrs: { type: 'module' },
+              children: `
+              import.meta.hot.on('test:ready', () => {
+                document.documentElement.dataset.hmrReady = 'true'
+              })
+              import.meta.hot.send('test:ready')
+            `,
+            },
+          ]
+        },
+      },
+    },
     {
       name: 'mock-custom',
       async hotUpdate({ file, read }) {
diff --git a/playground/test-utils.ts b/playground/test-utils.ts
index 038a5a8a34bedd..a6c07f0ee885c5 100644
--- a/playground/test-utils.ts
+++ b/playground/test-utils.ts
@@ -25,7 +25,6 @@ import {
   page,
   sourcemapSnapshot,
   testDir,
-  viteServer,
   watchBuilds,
 } from './vitestSetupUtils'
 
@@ -282,16 +281,6 @@ export function readDepOptimizationMetadata(
   )
 }
 
-export async function gotoLatestBuild(url: string): Promise<void> {
-  if (isBundledDev) {
-    // Earlier HMR edits leave the bundled-dev output stale. Opening a page then
-    // serves the fallback page first, which reloads into the real page later.
-    const bundledDev = viteServer.environments.client.bundledDev as any
-    await bundledDev.devEngine.ensureLatestBuildOutput()
-  }
-  await page.goto(url)
-}
-
 /**
  * Wait for every output containing the edited module to finish rebuilding.
  * Workaround for Rolldown emitting END per output before all outputs finish: