fix(loader): clone preset object

[huang-julien]

🔗 Linked issue

nuxt/test-utils#537
nuxt/test-utils#1043 ?

❓ Type of change

Hi 👋

This PR fix an issue with presets and will allow multiple Nuxt to be ran within the same process (like for vitest workspaces or its vscode extension)

Linked issues above are trying to run multiple nuxt at the same time. It means we need also to be able to start multiple nitro.

Here's the race condition.

Presets are objects and

nitro/src/core/config/loader.ts

Line 141 in e8d6099

config: preset,

returns directly the reference of the preset.

If we load 2 nitro at the same time, C12 can delete _layers on the preset object
https://github.com/unjs/c12/blob/67cf916ca727e584390196ce3d3bfb76aa102ec1/src/loader.ts#L267
and the other other may need _layer at that time (calling .push() for example) which will fail and throw an error.

(will this pr be merge in nitro 2 or does it need another pr ? )

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[pi0]

We should rebase it to v2

[pi0]

@huang-julien can you please rebase your PR against v2 branch?

[pi0]

@huang-julien Thanks for PR. as this change adds runtime cost (and there is no easy way to reproduce/confirm with nitro only) can you please try on nightly channel if it actually solved linked issues?

[huang-julien]

Thanks for merging this so fast ❤️

https://github.com/nuxt/nuxt/tree/repro/nitro-preset-shared-object here's the branch for reproduction in Nuxt. You need to run npx jiti ./loadNuxt.ts in test/fixtures/multiple-nuxt

It doesn't solve linked issues but allows to create the PR that will solve them in Nuxt.

[pi0]

That's a Nuxt reproduction. it was generally good safety fix thanks ❤️

[huang-julien]

ahhh so sorry about that

https://stackblitz.com/edit/unjs-nitro-starter-qxgcfv55?file=createNitro.ts&title=Nitro%20Starter
https://stackblitz.com/edit/unjs-nitro-starter-y8dt79gv?file=createNitro.ts,patches%2Fnitropack.patch,package.json,nitro.config.ts&title=Nitro%20Starter

you can run npx jiti createNitro.ts in both stackblitz