--merge-reports option not generate coverage as expected

[liam61]

Describe the bug

Hi, I just create a project from latest vite and vitest, and test the --shared and --merge-reports option.
But not collect the right coverage percentage, the coverage-final.json file is empty!

Reproduction

1. yarn vite create
2. add vitest dependence
3. add simple tests
4. use --shared and --merge-reports option

System Info

System:
    OS: macOS 13.4
    CPU: (12) x64 Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz
    Memory: 116.41 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 18.20.3 - ~/.nvm/versions/node/v18.20.3/bin/node
    Yarn: 1.22.22 - ~/.nvm/versions/node/v18.20.3/bin/yarn
    npm: 10.7.0 - ~/.nvm/versions/node/v18.20.3/bin/npm
  Browsers:
    Chrome: 129.0.6668.101
    Safari: 16.5
  npmPackages:
    @vitejs/plugin-react: ^4.3.3 => 4.3.3 
    @vitejs/plugin-react-swc: ^3.5.0 => 3.7.1 
    @vitest/browser: ^2.1.3 => 2.1.3 
    @vitest/coverage-v8: ^2.1.3 => 2.1.3 
    @vitest/ui: ^2.1.3 => 2.1.3 
    vite: ^5.4.8 => 5.4.9 
    vitest: ^2.1.3 => 2.1.3

Used Package Manager

yarn

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

[github-actions]

Hello @liam61. Please provide a minimal reproduction using a GitHub repository or StackBlitz (you can also use examples). Issues marked with needs reproduction will be closed if they have no activity within 3 days.