refactor(nuxt)!: move head option support into defineNuxtComponent

[danielroe]

🔗 Linked issue

https://github.com/nuxt/framework/discussions/8874

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 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)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This PR moves support for head option into defineNuxtComponent to allow proper tree-shaking of used composables and avoid registering a global mixin that runs on every single component.

This PR also removes legacy support for useMeta which has been deprecated for some time. useHead is a drop-in replacement.

👉 Migration

Anywhere you are using the Options API head hook, you can instead wrap the component with defineNuxtComponent. (Or alternatively you may decide to use a component like <Meta>, <Link>, etc.)

Anywhere you are using useMeta, you should replace useHead.

📝 Checklist

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

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[harlan-zw]

Oh nice, this is a good idea.

I'll make the mixin from #8908 opt-in

[pi0]

Any updates on this? 🙏🏼 What is a blocker?

[harlan-zw]

lgtm

[danielroe]

The issue at the moment is that this PR produces a separate, tiny _nuxt/composables.js chunk.

[danielroe]

I've looked into this a bit further and it seems inevitable from a rollup point of view, even if we were to move useHead into #app directly. The issue is that the error components (dynamically imported) are importing only useHead from app and rollup therefore produces a tiny shared chunk. We may be able to refine behaviour with manualChunks in future but I think it should be okay for now, and not replicable if a user is using their own error.vue.