Unused locales are included in the bundle

[ExEr7um]

Environment

• Operating System: Darwin
• Node Version: v24.8.0
• Nuxt Version: 4.1.2
• CLI Version: 3.28.0
• Nitro Version: 2.12.6
• Package Manager: pnpm@10.16.1
• Builder: -
• User Config: modules, devtools, css, routeRules, compatibilityDate, eslint
• Runtime Modules: @nuxt/eslint@1.9.0, @nuxt/ui@4.0.0-alpha.2
• Build Modules: -

Is this bug related to Nuxt or Vue?

Nuxt

Package

v4.0.0-alpha.x

Version

v4.0.0-alpha.2

Reproduction

https://github.com/ExEr7um/nuxt-ui-rolldown-locales-treeshake

Description

Unused locales are included in the bundle when using Rolldown. If I disable it, then only imported locales are present. Related to #3602.

Reproduction

Locales are imported in app.vue file like this:

import { en as nuxtUiEn, ru as nuxtUiRu } from '@nuxt/ui/locale'

Steps

1. Run pnpm dlx nuxi analyze.
2. Check client bundle, all locales are included.
3. Remove rolldown-vite override in package.json and run pnpm i.
4. Run pnpm dlx nuxi analyze again.
5. Check client bundle, only imported locales are present.

Additional context

No response

Logs

[benjamincanac]

@danielroe Do you know if the /* @__PURE__ */ and /* @__NO_SIDE_EFFECTS__ */ work the same with rolldown-vite? 🤔

[danielroe]

not sure! cc: @TheAlexLichter

[TheAlexLichter]

Cross chunk /* @__NO_SIDE_EFFECTS__ */ Just got added and released! rolldown/rolldown#3234

[ExEr7um]

@benjamincanac @TheAlexLichter I have updated rolldown and rolldown-vite in the reproduction repo, but the issue is still present. All locales are still in the output.

[TheAlexLichter]

@ExEr7um Let me have a look. Will open an issue in https://github.com/vitejs/rolldown-vite (as it needs to be fixed there, not in nuxt/ui 👍🏻)