Describe the bug

When a virtual module contains comments, directives, and unused variables, those are removed from the code that is available in the hook generateBundle.

This is a regression compared to v7, and undocumented breaking change from the migration guide.

At Astro, we rely on a top-level comment to use our head propagation strategy, however this breaks in v8 because the comment is stripped.

Previous issue #21814

Reproduction

https://github.com/ematipico/test-errors/tree/bug/stripping-correct

Steps to reproduce

• Checkout the repro
• Checkout branch bug/stripping-correct
• Run node build.mjs for single execution or run node build.mjs compare to compare v7 and v8

The output should show enough information

System Info

System:
    OS: macOS 26.4
    CPU: (12) arm64 Apple M4 Pro
    Memory: 3.67 GB / 48.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.12.0 - 
    npm: 11.6.2 - 
    pnpm: 10.28.0 - 
  Browsers:
    Firefox: 149.0
    Safari: 26.4
  npmPackages:
    vite: ^8.0.3 => 8.0.3

Used Package Manager

pnpm

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.