[v8] CJS interop factory shadowed when re-bundling rolldown-emitted CJS output

[williamlark]

Describe the bug

vite build silently generates broken code when bundling a CJS package whose files were themselves previously emitted by rolldown using "unbundle" mode.

The root cause is a naming collision: rolldown uses require_<filestem> as the variable name for its __commonJS factory wrappers. When a source file already contains a local variable with the same name (because it was previously emitted by rolldown), rolldown skips creating the outer factory, yet still replaces require("./file.cjs") with require_<X>() inside the wrapper body. The result is self-referencing code that crashes at runtime:

var require_greet = require_greet();  // require_greet is never defined — TypeError

Reproduction

https://github.com/williamlark/vite-rolldown-cjs-interop-collision

Steps to reproduce

Load the reproduction repo and pnpm install && pnpm build && pnpm preview

System Info

System:
    OS: macOS 26.3.1
    CPU: (12) arm64 Apple M3 Pro
    Memory: 88.06 MB / 18.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.22.2 - /[redacted]/.nvm/versions/node/v22.22.2/bin/node
    npm: 10.9.7 - /[redacted]/.nvm/versions/node/v22.22.2/bin/npm
    pnpm: 10.13.1 - /[redacted]/pnpm/pnpm
  Browsers:
    Chrome: 146.0.7680.178
    Edge: 146.0.3856.97
    Firefox: 149.0
    Safari: 26.3.1
  npmPackages:
    vite: ^8.0.5 => 8.0.5

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.

[vorobiovkirill]

Any ETA to fix ?

[eliottreich]

Rolldown-related issues are getting a lot of traction. There's a $35 bounty for this on Code.TaskBounty.

The idea is multiple developers compete on a fix — you get to compare solutions before picking one. This kind of CJS interop edge case is exactly the type of thing that benefits from competing approaches.

Bounty is open to anyone: https://code.task-bounty.com/task/vite-bundler-feature-rolldown

[redwing509]

/attempt #22176

Implementation plan:

1. Analyze the existing codebase and understand the requirements
2. Implement the requested changes with clean, tested code
3. Add comprehensive tests covering the acceptance criteria
4. Submit PR with documentation updates if needed

Estimated delivery: within 24 hours.