nuxt.options._layers is not iterable in v3.0.0

Environment

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• Operating System: Linux
• Node Version: v20.8.1
• Nuxt Version: 2.17.2
• CLI Version: 3.10.0
• Nitro Version: 2.8.1
• Package Manager: pnpm@8.14.1
• Builder: webpack
• User Config: -
• Runtime Modules: -
• Build Modules: -

---

Reproduction

The error only occurs in production after running :

yarn build
yarn start

Describe the bug

I am in the process of updating a module in our company from v3.0.0-rc.4 to v3.0.0

We're not using nitro and vite yet, as we still have some work to do.

Our module installs other modules using installModule function from @nuxt/kit.

The following error occurs when launching the server after a production build :

yarn run v1.22.19
$ nuxt2 start

 ERROR  nuxt.options._layers is not iterable                        7:37:51 PM

  at installModule (node_modules/@nuxt/kit/dist/index.mjs:2409:32)

I traced the error back to its source

If I understand correctly,

• Version v3.0.0-rc.4 uses version v3.8.2 of @nuxt/kit
• Version v3.0.0 uses version v3.9.1 of @nuxt/kit.
• The installModule function in v3.9.1 depends on the contents of the nuxt.options._layers property. L19
• The nuxt.options._layers property is mocked by @nuxt/bridge but only in dev environment or during the build process. L61
• This is the reason why the nuxt.options._layers property is undefined when the server is started.

Proposed solution:

• We need to mock _layers for nitro and auto-imports outside the buildModules function.
• This solves the issue locally

Additional context

No response

Logs

No response

Start with packages/bridge/module.cjs at the linked _layers mock and packages/kit/src/module/install.ts at installModule. Reproduce the production path with yarn build followed by yarn start, then verify that the server starts without the nuxt.options._layers error.