Regression in 8.2: Vitest `setupFiles` fails with "Cannot find module" across Windows drive symlinks

[ELowry]

Describe the bug

I am running a Vitest test suite on Windows where my project directory is accessed via a symlink across different drive letters (e.g., executing in C:\D-Data\... which is symlinked to D:\.Data\...).

When updating Vite from 8.1.5 to 8.2.0/1, running Vitest fails immediately with Error: Cannot find module '/vitest.setup.js'.
I believe that the path resolution for setupFiles gets stripped down to the absolute root of the C: drive when resolving across the symlinked drives.

Rolling Vite back to 8.1.5 completely resolves the issue without any configuration changes.

I strongly suspect this regression was introduced in v8.2.0-beta.0 by PR #22832 (resolve root to real path), which may be incorrectly forcing the root to the real path (D:) and failing to respect the execution context or preserveSymlinks: true when Vitest attempts to load the virtual module.

Reproduction

https://github.com/ELowry/Vite-Symlink-Issue-Test-Repo

Steps to reproduce

1. Clone this repository on a Windows machine to a secondary drive (e.g., D:\.Data\vite-symlink-windows-bug).
2. Open an Administrator command prompt and create a directory junction/symlink on the primary drive pointing to it:
   mklink /J C:\D-Data\vite-symlink-windows-bug D:\.Data\vite-symlink-windows-bug
3. Open your terminal and navigate to the project via the symlinked path:
   cd C:\D-Data\vite-symlink-windows-bug
4. Run npm install
5. Run npm run test
6. Get the error: Error: Cannot find module '/vitest.setup.js'.
7. (optional) Downgrade Vite to 8.1.5 and test again, it should work without any errors.

System Info

System:
    OS: Windows 11 10.0.26200
    CPU: (16) x64 AMD Ryzen 7 5800X 8-Core Processor
    Memory: 10.49 GB / 31.93 GB
  Binaries:
    Node: 24.16.0 - C:\nvm4w\nodejs\node.EXE
    npm: 12.0.1 - C:\nvm4w\nodejs\npm.CMD
  Browsers:
    Chrome: 150.0.7871.187
    Edge: Chromium (151.0.4129.59)
    Firefox: 153.0.1 - C:\Program Files\Mozilla Firefox\firefox.exe
    Internet Explorer: 11.0.26100.8115
  npmPackages:
    vite: ^8.2.1 => 8.2.1

Used Package Manager

npm

Logs

Click to expand!

C:\D-Data\vite-symlink-repo [main ≡ +0 ~1 -0 !]> npm run test
npm notice run vite-symlink-repro@1.0.0 test
npm notice run vitest run

 RUN  v4.1.10 D:/.Data/vite-symlink-repo

 ❯ dummy.test.js (0 test)

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Failed Suites 1 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

 FAIL  dummy.test.js [ dummy.test.js ]
Error: Cannot find module '/vitest.setup.js'
⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[1/1]⎯


 Test Files  1 failed (1)
      Tests  no tests
   Start at  21:40:57
   Duration  983ms (transform 0ms, setup 0ms, import 0ms, tests 0ms, environment 810ms) 

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