fix(types): narrow down the return type of defineConfig

packages/vite/src/node/__tests__/config.spec.ts

@@ -7,7 +7,7 @@ import { mergeConfig } from '../publicUtils'
 
 describe('mergeConfig', () => {
   test('handles configs with different alias schemas', () => {
-    const baseConfig: UserConfigExport = {
+    const baseConfig = defineConfig({
       resolve: {
         alias: [
           {
@@ -16,16 +16,16 @@ describe('mergeConfig', () => {
           },
         ],
       },
-    }
+    })
 
-    const newConfig: UserConfigExport = {
+    const newConfig = defineConfig({
       resolve: {
         alias: {
           bar: 'bar-value',
           baz: 'baz-value',
         },
       },
-    }
+    })
 
     const mergedConfig: UserConfigExport = {
       resolve: {

packages/vite/src/node/config.ts

@@ -100,15 +100,26 @@ export interface ConfigEnv {
  */
 export type AppType = 'spa' | 'mpa' | 'custom'
 
+export type UserConfigFnObject = (env: ConfigEnv) => UserConfig
+export type UserConfigFnPromise = (env: ConfigEnv) => Promise<UserConfig>
 export type UserConfigFn = (env: ConfigEnv) => UserConfig | Promise<UserConfig>
-export type UserConfigExport = UserConfig | Promise<UserConfig> | UserConfigFn
+
+export type UserConfigExport =
+  | UserConfig
+  | Promise<UserConfig>
+  | UserConfigFnObject
+  | UserConfigFnPromise
+  | UserConfigFn
 
 /**
  * Type helper to make it easier to use vite.config.ts
  * accepts a direct {@link UserConfig} object, or a function that returns it.
  * The function receives a {@link ConfigEnv} object that exposes two properties:
  * `command` (either `'build'` or `'serve'`), and `mode`.
  */
+export function defineConfig(config: UserConfig): UserConfig
+export function defineConfig(config: Promise<UserConfig>): Promise<UserConfig>
+export function defineConfig(config: UserConfigExport): UserConfigExport
 export function defineConfig(config: UserConfigExport): UserConfigExport {
   return config
 }

playground/assets/vite.config.js

@@ -1,8 +1,6 @@
 import path from 'node:path'
 import { defineConfig } from 'vite'
 
-/** @type {import('vite').UserConfig} */
-// @ts-expect-error typecast
 export default defineConfig({
   base: '/foo',
   publicDir: 'static',

playground/css/vite.config.js

@@ -9,8 +9,6 @@ globalThis.window = {}
 // @ts-expect-error refer to https://github.com/vitejs/vite/pull/11079
 globalThis.location = new URL('http://localhost/')
 
-/** @type {import('vite').UserConfig} */
-// @ts-expect-error typecast
 export default defineConfig({
   build: {
     cssTarget: 'chrome61',

playground/define/vite.config.js

@@ -1,7 +1,5 @@
 import { defineConfig } from 'vite'
 
-/** @type {import('vite').UserConfig} */
-// @ts-expect-error typecast
 export default defineConfig({
   define: {
     __EXP__: 'false',

playground/lib/vite.config.js

@@ -2,8 +2,6 @@ import fs from 'node:fs'
 import path from 'node:path'
 import { defineConfig } from 'vite'
 
-/** @type {import('vite').UserConfig} */
-// @ts-expect-error typecast
 export default defineConfig({
   esbuild: {
     supported: {