feat(nuxt): custom cache support for data fetching composables

[darioferderber]

🔗 Linked issue

#20476
resolves #15445

❓ 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

Resolves #20476

This adds support for custom caching within useAsyncData and useFetch. It works by providing a getCachedData function via the options which receives a key and can return cached data if it exists. For example, to make all requests cached by default, the following options could be used:

const nuxtApp = useNuxtApp()
const { data } = await useAsyncData(() => { /* fetcher */ }, {
  // this will not refetch if the key exists in the payload
  getCachedData: key => nuxtApp.payload.static[key] || nuxtApp.payload.data[key]
})

📝 Checklist

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

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[danielroe]

I'm reluctant to merge this PR as it's really a feature to work around a bug.

What about instead supporting a cache/store option that defaults to nuxt.isHydrating ? nuxt.payload.data : nuxt.static.data? Then this could be set to a custom location, or forced to nuxt.payload.data, which would have the same effect as forcing payload extraction.

It could be part of #15445.

Thoughts @pi0?

[pi0]

More generic cache option with better defaults sound reasonably better alternative approach.

[danielroe]

Would it be possible to update this instead to take the cache/store option? 🙏

Thoughts welcome on best API.