previewTemplate serializes internal `info` collection's `source: undefined` as `source: []`

[humanbird]

Environment

• OS: macOS 15.4 (Darwin 25.4.0 arm64)
• Node: v24.13.0
• Nuxt: 4.4.2
• @nuxt/content: 3.12.0
• nuxt-studio: 1.6.0

Version

3.12.0

Reproduction

The bug is in the compiled source at dist/module.mjs and can be verified by inspecting the /__preview.json endpoint output. Steps:

1. Create a Nuxt 4 project with @nuxt/content v3 and nuxt-studio
2. Define any content collections in content.config.ts
3. Deploy with SSR and navigate to /__preview.json
4. Observe that the info collection has "source": [] instead of being excluded or having source omitted

Description

The internal info collection created by resolveCollections() has source: void 0 (line 2405 of dist/module.mjs):

collections.info = {
  type: "data",
  source: void 0,
  schema: infoStandardSchema,
  // ...
};

The previewTemplate() function (line 1701) serializes this into source: []:

source: collection.source?.filter((source) => source.repository ? void 0 : collection.source) || [],

Since undefined?.filter(...) evaluates to undefined, the || [] fallback kicks in, producing source: [] in the serialized output.

This causes downstream crashes in nuxt-studio, which iterates all collections and accesses source[0].include / source[0].prefix without guarding against empty arrays — resulting in TypeError: Cannot read properties of undefined (reading 'include').

See also: nuxt-content/nuxt-studio#425

Suggested fix

Either exclude collections without source from the preview payload:

// In previewTemplate, skip the info collection
if (!collection.source) return acc;

Or use ?? instead of || to preserve the distinction:

source: collection.source?.filter((source) => source.repository ? void 0 : collection.source) ?? undefined,

(With ?? undefined, JSON.stringify will omit the key entirely.)

I'm happy to submit a PR if you'd prefer one approach over the other.

Additional context

The nuxt-studio side also lacks null guards (tracked in nuxt-content/nuxt-studio#425), but the root cause is the serialization here — source: void 0 should not become source: [] in the preview payload.

Logs

TypeError: Cannot read properties of undefined (reading 'include')
    at parseSourceBase (source.js)
    at Array.map
    at async Object.list
    at async Object.load (main-CUjoLU7k.js)