fix(css): empty CSS entry points should generate CSS files, not JS files

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

@@ -824,7 +824,7 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
         }
       }
 
-      if (chunkCSS) {
+      if (chunkCSS || (isPureCssChunk && chunk.isEntry)) {
         if (isPureCssChunk && (opts.format === 'es' || opts.format === 'cjs')) {
           // this is a shared CSS-only chunk that is empty.
           pureCssChunks.add(chunk)

playground/css/__tests__/empty-css/empty-css.spec.ts

@@ -0,0 +1,22 @@
+import { readFileSync } from 'node:fs'
+import { join } from 'node:path'
+import { describe, expect, test } from 'vitest'
+import { isBuild, readManifest } from '~utils'
+
+describe.runIf(isBuild)('empty CSS entries', () => {
+  test('empty CSS files should generate .css assets, not .js assets', () => {
+    const manifest = readManifest()
+
+    // Test that empty.css generates a CSS file
+    expect(manifest['empty.css']).toBeDefined()
+    expect(manifest['empty.css'].file).toMatch(/\.css$/)
+    expect(manifest['empty.css'].file).not.toMatch(/\.js$/)
+    expect(manifest['empty.css'].isEntry).toBe(true)
+
+    // Test that empty2.css generates a CSS file
+    expect(manifest['empty2.css']).toBeDefined()
+    expect(manifest['empty2.css'].file).toMatch(/\.css$/)
+    expect(manifest['empty2.css'].file).not.toMatch(/\.js$/)
+    expect(manifest['empty2.css'].isEntry).toBe(true)
+  })
+})

playground/css/empty.css

@@ -0,0 +1 @@
+/* This is an empty CSS file for testing empty CSS entries */

playground/css/vite.config.js

@@ -39,13 +39,16 @@ export default defineConfig({
   ],
   build: {
     cssTarget: 'chrome61',
+    manifest: true,
     rollupOptions: {
       input: {
         index: path.resolve(__dirname, './index.html'),
         treeshakeScoped: path.resolve(
           __dirname,
           './treeshake-scoped/index.html',
         ),
+        empty: path.resolve(__dirname, './empty.css'),
+        empty2: path.resolve(__dirname, './empty2.css'),
       },
       output: {
         manualChunks(id) {