feat(nuxt): server-only pages

[huang-julien]

🔗 Linked issue

❓ Type of change

#19772

• 📖 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

Hi 👋 this PR allows users to define pages as server page with definePageMeta() and the .server.vue suffix in the filename.

in definePageMeta this PR took #25037 as reference for the field name : mode. For now it only accept undefined or 'server'. For the client only implementation, see #25037

📝 Checklist

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

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[danielroe]

I think this will make it much harder to cache server islands as the hash we create will vary by path.

Could we instead pass this as part of the context via createIslandPage instead (and maybe use route.path to skip query/hash)?

[huang-julien]

I think we should not skip query 🤔, userss tend to relly on it within pages composables. Maybe can we pass an object like

{
  path: string,
query?: Record<string, string>
}

?

[danielroe]

The issue is (for example) that we will make a separate request for every query variation, which wouldn't be compatible with static sites and allow cache-busting by passing arbitrary query params or hashes ... (We should definitely not pass hash.) We could document this as a limitation of server pages... Or at a minimum, skip passing the full route if the route matches prerender routeRule?

[huang-julien]

I see, let's start by passing only the path in the context then 🤔. and iterate on it, i'm not sure what kind of side effect we can have if using fullPath with ssg

[danielroe]

this looks great to me.

I do think we probably could respect the route query as long as it's not a prerendered page. (We can use isPrerendered to tell us.).

And I think we should drop the support for defining server-only pages within definePageMeta, which means that it's impossible to tree-shake this code out of the bundle, if even one page has any metadata at all.

[brc-dd]

There seems to be an issue with this if you try to directly access the server-only page in dev:

[nitro] [unhandledRejection] FetchError: [GET] "/_nuxt/builds/meta/dev.json": 404 Page not found: /_nuxt/builds/meta/dev.json
    at async $fetch2 (file:///Users/brc-dd/nuxt-app/node_modules/.pnpm/ofetch@1.3.3/node_modules/ofetch/dist/shared/ofetch.00501375.mjs:261:15)
[Vue warn]: Component foo is missing template or render function.

It works fine if you open home first and then go to server-only page via link 👀