fix(css): dont remove JS chunk for pure CSS chunk when the export is used (#18307)

Author: sapphi-red

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

@@ -568,7 +568,7 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
       let chunkCSS = ''
       // the chunk is empty if it's a dynamic entry chunk that only contains a CSS import
       const isJsChunkEmpty = code === '' && !chunk.isEntry
-      let isPureCssChunk = true
+      let isPureCssChunk = chunk.exports.length === 0
       const ids = Object.keys(chunk.modules)
       for (const id of ids) {
         if (styles.has(id)) {

playground/glob-import/vite.config.ts

@@ -24,5 +24,14 @@ export default defineConfig({
   },
   build: {
     sourcemap: true,
+    rollupOptions: {
+      output: {
+        manualChunks(id) {
+          if (id.includes('foo.css')) {
+            return 'foo_css'
+          }
+        },
+      },
+    },
   },
 })