From b1e0628b6a5dd541e15166ca6666e05f9b478ab8 Mon Sep 17 00:00:00 2001
From: sapphi-red <49056869+sapphi-red@users.noreply.github.com>
Date: Fri, 10 Apr 2026 12:44:03 +0900
Subject: [PATCH 1/3] fix(build): emptyOutDir should happen for watch rebuilds

---
 .../vite/src/node/plugins/prepareOutDir.ts    |  2 +-
 playground/assets/__tests__/assets.spec.ts    | 21 +++++++++++++++++++
 playground/assets/asset/update.js             |  4 ++++
 playground/assets/index.html                  |  2 ++
 playground/vitestSetup.ts                     |  2 --
 5 files changed, 28 insertions(+), 3 deletions(-)
 create mode 100644 playground/assets/asset/update.js

diff --git a/packages/vite/src/node/plugins/prepareOutDir.ts b/packages/vite/src/node/plugins/prepareOutDir.ts
index 9ee4b3c4b9419c..4117e63bb5e17f 100644
--- a/packages/vite/src/node/plugins/prepareOutDir.ts
+++ b/packages/vite/src/node/plugins/prepareOutDir.ts
@@ -11,7 +11,7 @@ export function prepareOutDirPlugin(): Plugin {
   const rendered = new Set<Environment>()
   return {
     name: 'vite:prepare-out-dir',
-    options() {
+    buildStart() {
       rendered.delete(this.environment)
     },
     renderStart: {
diff --git a/playground/assets/__tests__/assets.spec.ts b/playground/assets/__tests__/assets.spec.ts
index 8c8cd4ffe74f3d..89cfe2a78f4344 100644
--- a/playground/assets/__tests__/assets.spec.ts
+++ b/playground/assets/__tests__/assets.spec.ts
@@ -705,6 +705,27 @@ describe.runIf(isBuild)('css and assets in css in build watch', () => {
     expect(cssFile).not.toMatch(/undefined/)
   })
 
+  test('old file is removed when the content changes', async () => {
+    await expect.poll(() => page.textContent('.update-content')).toBe('hello')
+
+    const oldMainJsFiles = listAssets('foo').filter((f) =>
+      /index-[-\w]+\.js$/.test(f),
+    )
+    expect(oldMainJsFiles.length).toBe(1)
+    const oldMainJsFile = oldMainJsFiles[0]
+
+    editFile('asset/update.js', (code) => code.replace('hello', 'world'))
+    await notifyRebuildComplete(watcher)
+    await page.reload()
+    await expect.poll(() => page.textContent('.update-content')).toBe('world')
+
+    const newMainJsFiles = listAssets('foo').filter((f) =>
+      /index-[-\w]+\.js$/.test(f),
+    )
+    expect(newMainJsFiles).not.toContain(oldMainJsFile)
+    expect(newMainJsFiles.length).toBe(1)
+  })
+
   test('import module.css', async () => {
     expect(await getColor('#foo')).toBe('red')
     editFile('css/foo.module.css', (code) => code.replace('red', 'blue'))
diff --git a/playground/assets/asset/update.js b/playground/assets/asset/update.js
new file mode 100644
index 00000000000000..79b790f512ef45
--- /dev/null
+++ b/playground/assets/asset/update.js
@@ -0,0 +1,4 @@
+function text(el, text) {
+  document.querySelector(el).textContent = text
+}
+text('.update-content', 'hello')
diff --git a/playground/assets/index.html b/playground/assets/index.html
index 6b6eac7f2df73b..77f7ea4add1a44 100644
--- a/playground/assets/index.html
+++ b/playground/assets/index.html
@@ -482,7 +482,9 @@ <h3>assets in template</h3>
 <link rel="stylesheet" href="asset/style.css" />
 <div class="relative-css">link style</div>
 <div class="relative-js"></div>
+<div class="update-content"></div>
 <script src="asset/main.js" type="module"></script>
+<script src="asset/update.js" type="module"></script>
 <style>
   @import '/foo.css';
 </style>
diff --git a/playground/vitestSetup.ts b/playground/vitestSetup.ts
index 17bbc40755f4ac..6bfe32282a92bd 100644
--- a/playground/vitestSetup.ts
+++ b/playground/vitestSetup.ts
@@ -265,8 +265,6 @@ async function loadConfig(configEnv: ConfigEnv) {
       // esbuild do not minify ES lib output since that would remove pure annotations and break tree-shaking
       // skip transpilation during tests to make it faster
       target: 'esnext',
-      // tests are flaky when `emptyOutDir` is `true`
-      emptyOutDir: false,
     },
     customLogger: createInMemoryLogger(serverLogs),
     plugins: [throwHtmlParseError()],

From 413c537ce9e3ebc20ba25bd6a76b60e1d4705bc1 Mon Sep 17 00:00:00 2001
From: sapphi-red <49056869+sapphi-red@users.noreply.github.com>
Date: Fri, 10 Apr 2026 13:06:20 +0900
Subject: [PATCH 2/3] test: fix legacy playground

---
 playground/legacy/vite.config.js | 1 +
 1 file changed, 1 insertion(+)

diff --git a/playground/legacy/vite.config.js b/playground/legacy/vite.config.js
index c822b5d60b066b..8b5884f7943cad 100644
--- a/playground/legacy/vite.config.js
+++ b/playground/legacy/vite.config.js
@@ -17,6 +17,7 @@ export default defineConfig({
     manifest: true,
     sourcemap: true,
     assetsInlineLimit: 100, // keep SVG as assets URL
+    emptyOutDir: false, // the dist directory is shared with other configs
     rollupOptions: {
       input: {
         index: path.resolve(import.meta.dirname, 'index.html'),

From e61d8ce83376309e031960f3821855c2bd57c239 Mon Sep 17 00:00:00 2001
From: sapphi-red <49056869+sapphi-red@users.noreply.github.com>
Date: Fri, 10 Apr 2026 13:51:11 +0900
Subject: [PATCH 3/3] fix: buildStart is called for each output

---
 packages/vite/src/node/plugins/prepareOutDir.ts | 2 +-
 playground/css/vite.config.js                   | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/vite/src/node/plugins/prepareOutDir.ts b/packages/vite/src/node/plugins/prepareOutDir.ts
index 4117e63bb5e17f..eb8fd6554c6d21 100644
--- a/packages/vite/src/node/plugins/prepareOutDir.ts
+++ b/packages/vite/src/node/plugins/prepareOutDir.ts
@@ -11,7 +11,7 @@ export function prepareOutDirPlugin(): Plugin {
   const rendered = new Set<Environment>()
   return {
     name: 'vite:prepare-out-dir',
-    buildStart() {
+    watchChange() {
       rendered.delete(this.environment)
     },
     renderStart: {
diff --git a/playground/css/vite.config.js b/playground/css/vite.config.js
index 76dc4395aeac39..937a2dd4e54dfc 100644
--- a/playground/css/vite.config.js
+++ b/playground/css/vite.config.js
@@ -55,6 +55,7 @@ export default defineConfig({
         },
       },
     },
+    emptyOutDir: false, // the dist directory is shared with other configs
   },
   esbuild: {
     logOverride: {