[v5.2.2 regression] Scoped CSS completely missing from named exports in Options API components

[kjeksfjes]

Related plugins

• plugin-vue

• plugin-vue-jsx

Describe the bug

Summary

@vitejs/plugin-vue v5.2.2+ drops scoped CSS from Options API components using named exports. CSS is completely missing from the bundle with no build errors or warnings.

Regression: v5.2.2 (last working: v5.2.1)
Status: Still broken in v6.0.2

Minimal Reproduction

<!-- TestComponent.vue -->
<script>
import { defineComponent } from 'vue'

// Named export - triggers the bug
export const TestComponent = defineComponent({
  name: 'TestComponent',
  data() {
    return { message: 'Hello' }
  }
})
</script>

<template>
  <div class="TestComponent">{{ message }}</div>
</template>

<style scoped>
.TestComponent { background: blue; }
</style>

<!-- App.vue -->
<script setup>
import { TestComponent } from './TestComponent.vue'
</script>
<template>
  <TestComponent />
</template>

Config: Default Vite config, no special plugins needed.

The Issue

Broken (v5.2.2+):

export const MyComponent = defineComponent({...})  // CSS missing

Works:

export default defineComponent({...})  // CSS present

Expected vs Actual

Expected: CSS in bundle with scoped selectors like .TestComponent[data-v-abc123]{background:blue}

Actual: No CSS anywhere in dist/ output. Component renders but completely unstyled.

Steps to Reproduce

1. Create component with export const X = defineComponent({...}) + <style scoped>
2. Import via import { X } from './Component.vue'
3. Run vite build with plugin-vue v5.2.2+
4. CSS is missing from output

Environment

• @vitejs/plugin-vue: v6.0.2 (broken), v5.2.1 (works)
• vite: 7.2.4
• vue: 3.5.22

Tested versions:

• ✅ v5.2.1 and earlier - Works
• ❌ v5.2.2 through v6.0.2 - Broken

Analysis

Starting in v5.2.2, tree-shaking doesn't properly track scoped CSS dependencies for named exports. The v5.2.2 CHANGELOG mentions "use transformWithOxc if rolldown-vite is detected" - possibly related.

Workaround

Downgrade to v5.2.1:

npm install -D @vitejs/plugin-vue@5.2.1

Or use default exports (not feasible for patterns requiring named exports like JSONForms).

Impact

• Silent failure affecting production builds
• Common in component libraries and JSONForms renderers
• Forces migration away from named export patterns

Reproduction

https://github.com/kjeksfjes/vite-plugin-vue-named-export-bug

Steps to reproduce

Reproduction Steps

1. Clone the reproduction repo and install dependencies:

   git clone https://github.com/kjeksfjes/vite-plugin-vue-named-export-bug.git
   cd vite-plugin-vue-named-export-bug
   npm install
   

2. Build the project (bug occurs during production build):
   npm run build

3. Check if CSS is present in the output:
   grep "TestComponent.\*background" dist/assets/\*.css

4. Expected: CSS found with scoped selectors
   Actual: No results - CSS is completely missing

5. (Optional) Test that v5.2.1 works correctly:
   npm install -D @vitejs/plugin-vue@5.2.1
npm run build
grep "TestComponent.*background" dist/assets/*.css
   ✅ CSS is present in v5.2.1

Note: The bug affects production builds only. Dev mode (npm run dev) works correctly - the issue only manifests when running npm run build.

System Info

System:
    OS: macOS 26.1
    CPU: (10) arm64 Apple M1 Max
    Memory: 68.38 MB / 64.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.17.0 - /Users/joakim/.nvm/versions/node/v22.17.0/bin/node
    Yarn: 1.22.22 - /Users/joakim/.nvm/versions/node/v22.17.0/bin/yarn
    npm: 10.9.2 - /Users/joakim/.nvm/versions/node/v22.17.0/bin/npm
    pnpm: 10.12.4 - /Users/joakim/.nvm/versions/node/v22.17.0/bin/pnpm
  Browsers:
    Brave Browser: 134.1.76.74
    Chrome: 142.0.7444.176
    Edge: 142.0.3595.94
    Firefox: 140.0
    Safari: 26.1
  npmPackages:
    @vitejs/plugin-vue: ^6.0.2 => 6.0.2 
    vite: 7.2.4 => 7.2.4

Used Package Manager

npm

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• The provided reproduction is a minimal reproducible example of the bug.