fix(ssr): properly transform export default with expressions

packages/vite/src/node/ssr/__tests__/ssrTransform.spec.ts

@@ -657,3 +657,26 @@ export function fn1() {
             "
   `)
 })
+
+// https://github.com/vitest-dev/vitest/issues/1141
+test('export default expression', async () => {
+  // esbuild transform result of following TS code
+  // export default <MyFn> function getRandom() {
+  //   return Math.random()
+  // }
+  const code = `
+export default (function getRandom() {
+  return Math.random();
+});
+`.trim()
+
+  expect((await ssrTransform(code, null, null)).code).toMatchInlineSnapshot(`
+    "__vite_ssr_exports__.default = (function getRandom() {
+      return Math.random();
+    });"
+  `)
+
+  expect(
+    (await ssrTransform(`export default (class A {});`, null, null)).code
+  ).toMatchInlineSnapshot(`"__vite_ssr_exports__.default = (class A {});"`)
+})

packages/vite/src/node/ssr/ssrTransform.ts

@@ -143,7 +143,12 @@ export async function ssrTransform(
 
     // default export
     if (node.type === 'ExportDefaultDeclaration') {
-      if ('id' in node.declaration && node.declaration.id) {
+      const expressionTypes = ['FunctionExpression', 'ClassExpression']
+      if (
+        'id' in node.declaration &&
+        node.declaration.id &&
+        !expressionTypes.includes(node.declaration.type)
+      ) {
         // named hoistable/class exports
         // export default function foo() {}
         // export default class A {}