feat!: universal head injection, drop activeHead

[harlan-zw]

🔗 Linked issue

❓ Type of change

• 📖 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

This change drops the use of the implicit shared context provided by the activeHead export. Now we explicitly have the user opt-in to a shared head instance or they need to provide their own function to resolve the context.

⚠️ Breaking Changes

• Removes the import getActiveHead(), instead you should use injectHead().
• Does not automatically set a global head instance for servers, you will need to apply the context manually.

If you're not processing requests in parallel (such as a testing environment) then doing something like this is safe

const head = createSharedHead()

// just works - will leak in a server environment across parallel requests
useHead({ title: 'hello world' })

Otherwise, you will need to attach the head to a context and use that. For example, in Nuxt we do the below. The useNuxtApp() context is provided with unctx.

setHeadInjectionHandler(() => useNuxtApp().vueApp._context.provides.usehead)

Note: It's important not to pass in a reference to a context within this function unless you're share it will be unique accross requests.

// bad
const nuxtApp = useNuxtApp() // context will leak across requests
setHeadInjectionHandler(() => nuxtApp.vueApp._context.provides.usehead)

📝 Checklist

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

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Name	Status	Preview	Comments	Updated (UTC)
unjs-unhead	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 14, 2023 5:10pm