fix: legacy no emit worker (#9500)

packages/vite/src/node/plugins/worker.ts

@@ -351,14 +351,19 @@ export function webWorkerPlugin(config: ResolvedConfig): Plugin {
           )
         }
       }
-      if (!isWorker) {
-        const workerMap = workerCache.get(config)!
-        workerMap.assets.forEach((asset) => {
-          this.emitFile(asset)
-          workerMap.assets.delete(asset.fileName!)
-        })
-      }
       return result()
+    },
+
+    generateBundle(opts) {
+      // @ts-ignore asset emits are skipped in legacy bundle
+      if (opts.__vite_skip_asset_emit__ || isWorker) {
+        return
+      }
+      const workerMap = workerCache.get(config)!
+      workerMap.assets.forEach((asset) => {
+        this.emitFile(asset)
+        workerMap.assets.delete(asset.fileName!)
+      })
     }
   }
 }

playground/legacy/__tests__/legacy.spec.ts

@@ -8,22 +8,32 @@ import {
   untilUpdated
 } from '~utils'
 
+test('should load the worker', async () => {
+  await untilUpdated(() => page.textContent('.worker-message'), 'module', true)
+})
+
 test('should work', async () => {
-  expect(await page.textContent('#app')).toMatch('Hello')
+  await untilUpdated(() => page.textContent('#app'), 'Hello', true)
 })
 
 test('import.meta.env.LEGACY', async () => {
-  expect(await page.textContent('#env')).toMatch(isBuild ? 'true' : 'false')
+  await untilUpdated(
+    () => page.textContent('#env'),
+    isBuild ? 'true' : 'false',
+    true
+  )
 })
 
 // https://github.com/vitejs/vite/issues/3400
 test('transpiles down iterators correctly', async () => {
-  expect(await page.textContent('#iterators')).toMatch('hello')
+  await untilUpdated(() => page.textContent('#iterators'), 'hello', true)
 })
 
 test('wraps with iife', async () => {
-  expect(await page.textContent('#babel-helpers')).toMatch(
-    'exposed babel helpers: false'
+  await untilUpdated(
+    () => page.textContent('#babel-helpers'),
+    'exposed babel helpers: false',
+    true
   )
 })
 

playground/legacy/index.html

@@ -6,5 +6,7 @@
 <div id="assets"></div>
 <button id="dynamic-css-button">dynamic css</button>
 <div id="dynamic-css"></div>
+<p>## worker message:</p>
+<div class="worker-message"></div>
 <div id="asset-path"></div>
 <script type="module" src="./main.js"></script>

playground/legacy/main.js

@@ -1,5 +1,6 @@
 import './style.css'
 import viteSvgPath from './vite.svg'
+import MyWorker from './worker?worker'
 
 async function run() {
   const { fn } = await import('./async.js')
@@ -56,3 +57,9 @@ text('#asset-path', viteSvgPath)
 function text(el, text) {
   document.querySelector(el).textContent = text
 }
+
+const worker = new MyWorker()
+worker.postMessage('ping')
+worker.addEventListener('message', (ev) => {
+  text('.worker-message', JSON.stringify(ev.data))
+})

playground/legacy/module.js

@@ -0,0 +1 @@
+export const module = 'module'

playground/legacy/worker.js

@@ -0,0 +1,5 @@
+import { module } from './module'
+
+self.onmessage = () => {
+  self.postMessage(module)
+}