fix(css)!: remove default import in ssr dev (#17922)

Co-authored-by: patak <583075+patak-dev@users.noreply.github.com>

Author: bluwy

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

@@ -539,13 +539,12 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
         if (isDirectCSSRequest(id)) {
           return null
         }
-        // server only
-        if (this.environment.config.consumer !== 'client') {
-          return modulesCode || `export default ${JSON.stringify(css)}`
-        }
         if (inlined) {
           return `export default ${JSON.stringify(css)}`
         }
+        if (this.environment.config.consumer === 'server') {
+          return modulesCode || 'export {}'
+        }
 
         const cssContent = await getContentWithSourcemap(css)
         const code = [

packages/vite/src/node/ssr/runtime/__tests__/server-runtime.spec.ts

@@ -32,12 +32,7 @@ describe('module runner initialization', async () => {
 
   it('css is loaded correctly', async ({ runner }) => {
     const css = await runner.import('/fixtures/test.css')
-    expect(css.default).toMatchInlineSnapshot(`
-      ".test {
-        color: red;
-      }
-      "
-    `)
+    expect(css.default).toBe(undefined)
     const module = await runner.import('/fixtures/test.module.css')
     expect(module).toMatchObject({
       default: {