feat(nuxt): config options for default keepalive, page & layout transitions

[danielroe]

🔗 Linked issue

resolvesnuxt/nuxt#14265

❓ 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 allows support for configuring page & layout transition default values, as well as keepalive. (Otherwise there is the tedious task of doing so for every individual file.)

In order to do this, we now inject #build/app.config.mjs to automatically expose all values within the app key in Nuxt config, rather than creating ever-more virtual files for particular use-cases. (We would, for example, have had to do this for layouts and page transitions separately otherwise.) This means we were able to drop meta.config.mjs and in general is a useful pattern for future app configuration.

📝 Checklist

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

[netlify]

✅ Deploy Preview for nuxt3-docs canceled.

Name	Link
🔨 Latest commit	a414fcd
🔍 Latest deploy log	https://app.netlify.com/sites/nuxt3-docs/deploys/6304c375fa5ce1000818a2af

[pi0]

Thanks for rebasing. Shall we type appConfig.nuxt from schema now?

[atinux]

Beautiful work @danielroe ❤️

Shall we document more to use app.config.ts for such configurations from now on?

[pi0]

Shall we document more to use app.config.ts for such configurations from now on?

Currently, usage of useAppConfig().nuxt is kinda internal. For some, we might have built-time optimization opportunities (like not bundling transition bytes) while if we make users able to set via app.config, we cannot do this anymore as such config can be changed on runtime. I suggest not adding nuxt types from AppConfigInput as well for this PR (keep marking it as never for input but typing for AppConfig)

[pi0]

(fixture seems broken)

[atinux]

Could we take this opportunity to also give the possibility to set those values to false to disable keepalive, page & layout transitions?

[danielroe]

Indeed, that is one of the key use-cases of this PR. As implemented here, it is possible to set them to false and it will disable keepalive, page & layout transitions.

[pi0]

For this, we could have a bundler flag (like NUXT_PAGE_TRANSITION) that replaces value to false on build time otherwise setting app config to false won't be able to tree-shake... (but can be later. pointing to make clear about false handling with this PR)

[danielroe]

Yes. This PR does not enable tree-shaking out; it just sets default behaviour. We can't tree shake this way as user may wish to enable transitions/keepalive on a per-page basis.

[danielroe]

I would love to be able to tree-shake out the Transition/Keepalive components but will it would need a different approach than this PR.

[pi0]

That's true. We use appConfig currently only to specify default but could be also used to specify feature flags. (swapping condition order when value is false to always disable transitions which I think would make more sense for false handling)

[danielroe]

Maybe support an additional option, e.g. keepalive: 'disabled' as the user may simply wish to disable them by default but not for all routes?

[pi0]

Thinking more about approaches, i think for specific nuxt bundled config, using an internal template with named exports (#build/nuxt.config.mjs ?) could be safer since we probably don't need nor could support HMR for these configs originating from nuxt.config and it makes it consistent with feature plans being able to treeshake at build time (appConfig is totally runtime-dynamic. we cannot depend on it for this unless passing another build flag)

[danielroe]

Okay - so just to confirm, we'll refactor back to original approach of this PR, but using nuxt.config.mjs filename?

[pi0]

LGTM.