Cannot edit the config after calling defineConfig anymore

[ST-DDT]

Describe the bug

After the update from 1.0.0-beta.1 to 1.0.0-beta.2 I get a type error when trying to alter the config:

Reproduction

const config = defineConfig({ ... });

if (versionBannerInfix) {
  config.head?.push([
    'script',
    { id: 'restore-banner-preference' },
    `someScript()`,
  ]);
}

export default config;

Working reproduction: https://github.com/faker-js/faker/blob/a6f5a39fff65d8923aab6db8a05a3ab79d097896/docs/.vitepress/config.ts#L257-L272

Expected behavior

I expect it to still work.

System Info

System:
    OS: Windows 10 10.0.22621
    CPU: (16) x64 Intel(R) Core(TM) i7-7820X CPU @ 3.60GHz
    Memory: 52.73 GB / 63.69 GB
  Binaries:
    Node: 18.16.0 - C:\Program Files\nodejs\node.EXE
    npm: 8.16.0 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Spartan (44.22621.1848.0), Chromium (114.0.1823.51)
    Internet Explorer: 11.0.22621.1
  npmPackages:
    vitepress: 1.0.0-beta.2 => 1.0.0-beta.2

Additional context

Found here: faker-js/faker#2216

// Vitepress Types
type UserConfigExport<ThemeConfig> = UserConfig<ThemeConfig> | Promise<UserConfig<ThemeConfig>> | UserConfigFn<ThemeConfig>;

declare function defineConfig(config: UserConfigExport<DefaultTheme.Config>): UserConfigExport<DefaultTheme.Config>;

The first UserConfigExport variant is a somewhat special case as it is the only that makes sense to change afterwards.

Fix:

Export two signatures:

declare function defineConfig(config: UserConfig<DefaultTheme.Config>): UserConfig<DefaultTheme.Config>;
declare function defineConfig(config: UserConfigExport<DefaultTheme.Config>): UserConfigExport<DefaultTheme.Config>;

Validations

• Check if you're on the latest VitePress version.
• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.

[brc-dd]

Ah yeah. We are aware of this. I'll push the changes with overloads tomorrow. It broke typings in some other plugins too. If it's blocking, you can use ts-ignore for now. (Only the types were broken, the functionality is same as earlier.)

[ST-DDT]

If it's blocking

It doesn't really block us, only the dependency update.

[brc-dd]

Okay, so what you suggested, and what I had initially in mind won't work. It breaks typings for patterns like these:

defineConfig(() => ({ // <-- can be async, doesn't work unless you add empty parameter (_) or ({})
  // complex stuff here (like our own docs config)
}))

There was an attempt at narrowing types in Vite too: vitejs/vite#12021, vitejs/vite#12077 -- that broke typings and intellisense too 👀

TS is getting kind of confused between promises and functions.

At the moment I'd recommend you to directly import UserConfig and DefaultTheme:

import type { UserConfig, DefaultTheme } from 'vitepress'

const config: UserConfig<DefaultTheme.Config>  = { ... }