feat(nuxt): add <NuxtLoadingIndicator> component

[antfu]

🔗 Linked issue

resolves https://github.com/nuxt/framework/discussions/2100

Based on @atinux's implementation.

❓ 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)

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[pi0]

Thanks for the PR @antfu. As we discussed in discord earlier, it might worth to pend this addition to base component based on a stable API for progress handling (Old discussions why needed: nuxt-community/axios-module#247, nuxt/http#105)

Also we would probably rename component to something more generic such as <NuxtLoadingIndicator> so that user's can override indicator behavior with something that is not essentially represented as a bar.

[atinux]

So what are the next steps?

I believe this is still a good improvements in term of UX and is completely optional.

I think we can also see progressively about the usage and feedback from users for improving it step by step without breaking it.

[antfu]

We could use provide / inject and a wrapper utility useLoadingIndicator() to expose the API for the module to control it. But that would rather be an advanced usage to me, and probably not blocking this have this for now.

[atinux]

I agree. I prefer the useLoadingBar() naming instead of indicator, or it should be named useProgressIndicator().

Would love also your feedback on naming @danielroe

[pi0]

In order to progress on this PR, we have to finalize naming at least.

Introducing core API for loading state can be in a follow-up PR but we should consider it changes the usage scope of the component as the current component depends on pages: hooks and works with pages/ directory only. And once we introduce core-api, it will be a universal component also with different behavior which triggers on data-fetching calls in addition to page navigations.

Regarding naming, while progress and bar represent built-in default behavior, the bar isn't essentially a representation of a customized indicator such as a rotating circle and Nuxt should be open to that or even provide customizable built-ins of different indicators! Using bar in the name prevents progress on this. API could be open to that and we had this chance only during v2 to v3 migration for improvement.

As summary:

• This PR: Keep minimal but decide on a future-proof naming for the component to land ASAP
• Followup PRs:
  • Introduce core API for loading indicator and refactor component to depend on it
  • Bind data-fetching composables to communicate with core API
  • Investigate different methods of overriding default indicator

[atinux]

I agree in the long term vision for sure!

For naming, I would vote for <NuxtProgressIndicator /> component, see https://en.wikipedia.org/wiki/Progress_indicator

[atinux]

I believe also that we need to change the place of page:start hook to be called before the middleware execution.

Some apps may use middleware for some data fetching.

[pi0]

I love the <NuxtProgressIndicator> naming 💯 Only it is not always percentage which was initially suggesting "Loading" as <NuxtLoadingIndicator> is which a broader definition of pending tasks (we currently even don't use a percentage but timers). What do you think would be finally the best?

Regarding ordering, for sure. We can either do the improvement here or later PR. I'm fine with both :) Anyway, the whole hooking system of the component needs to be changed once we migrate to the core API.

[atinux]

NuxtLoadingIndicator seems perfect, you are right since we cannot know about the percentage

[antfu]

To have the ability to do full customization, maybe we could use slot? Something like:

<NuxtLoadingIndicatorv-slot="{ percent, show, color }"><div>Custom rendering</div></NuxtLoadingIndicator>

So users could have the freedom to now present as a bar, without the need to handle the timers themselves.

[shiva-prasad-reddy]

In order to progress on this PR, we have to finalize naming at least.

Introducing core API for loading state can be in a follow-up PR but we should consider it changes the usage scope of the component as the current component depends on pages: hooks and works with pages/ directory only. And once we introduce core-api, it will be a universal component also with different behavior which triggers on data-fetching calls in addition to page navigations.

Regarding naming, while progress and bar represent built-in default behavior, the bar isn't essentially a representation of a customized indicator such as a rotating circle and Nuxt should be open to that or even provide customizable built-ins of different indicators! Using bar in the name prevents progress on this. API could be open to that and we had this chance only during v2 to v3 migration for improvement.

As summary:

• This PR: Keep minimal but decide on a future-proof naming for the component to land ASAP

• Followup PRs:

  • Introduce core API for loading indicator and refactor component to depend on it
  • Bind data-fetching composables to communicate with core API
  • Investigate different methods of overriding default indicator

In SPA, i have auth-middleware which does a onetime auth on a page reload, so i have added a loading indicator using page:start and page:finish hooks, i found that the page hooks are being called after the middleware is run so facing a white-screen delay.
Is there anyway that i could add some html or loading component to body in middleware and remove it at the end of middleware.

[atinux]

I believe we should also update to make sure the page:start is called before the middleware, what do you think @danielroe ?

[danielroe]

It does make sense to start this before middleware but I don't think we can move that hook. What about adding another one before middleware, and then finish loading on page: finish as before?

[atinux]

Makes sense, can we expose middleware:start and middleware:finish hooks in this PR? If so, where shall they be added @danielroe ?

[danielroe]

They will need to be added in:

• packages/nuxt/src/app/plugins/router.ts
• packages/nuxt/src/pages/runtime/router.ts

[atinux]

@antfu can you add them? 😊

[antfu]

I talked with @pi0 once, we were discuss about using something like progress:start, progress:end to be more specific to the loading indicator. Should we introduce both general ones and specific ones?

One other thing is that I am a bit concerned about more runtime hooks added to the bundle will cause the payload size to increase for every app?

[atinux]

What do you mean by the payload size to increase for every app? It will be the JS bundle growing, not the payload size (window.__NUXT__).

I rather see the <NuxtLoadingIndicator> acts based on our own hooks (middleware:start and page:finish) rather that some progress hooks at the moment.

Also, the devtools will be able to get some time mesurements between thoses hooks to help users speed up their apps.

[pi0]

I think Anthony refers to the bundle size for adding more bundle code (and also there is a slight runtime overhead of calling them)

Having middleware: hooks, in general, is a nice addition (and we can introduce it in a separate PR)

As of for controlling progress it might be trickier to depend state on multiple hooks (pages:, middleware: and later on data: for showing progress for pending asyncData fetchers). What would be the start and end of progress based on? middleware or pages or wait for both to end? In general, this is why I was insisting to introduce the loading API first to avoid having such concerns directly tied to the component implementation. Progress support was always tricky in Nuxt 2 when it comes to multiple sources of progress.

[atinux]

Well so far in both Nuxt 3 we have between two routes: Middleware -> Suspense(Pages + Components)

By using page:start and page:finish we are missing the Middleware, but this mean that is a middleware is aborting the navigation, we may not have the page:finish hook to stop the progress 😅

What you suggest is then to have the component listening to both loading:start and loading:finish and we call them directly in Nuxt code (but also giving freedom to end user to call them)?

[pi0]

What you suggest is then to have the component listening to both loading:start and loading:finish and we call them directly in Nuxt code (but also giving freedom to end-user to call them)?

[for the future] Yes. We render components based on loading: hooks (also loading:progress(percent)). Users don't have to call the hooks directly but use the API such as useNuxtProgress() to announce their tasks and progress on them individually. Nuxt will have to aggregate them. Both middleware system and pages announce their task to the same API as well.

Well so far in both Nuxt 3 we have two routes: Middleware -> Suspense(Pages + Components)

Makes sense. I think for this PR to move forward, if you like to also include progress for middleware, we can start with middleware:start and end with pages:finish. I would prefer to have a separate PR to introduce middleware: hooks for changelog clarity but that shouldn't be a blocker.

[atinux]

What we can do is to move forward by merging this PR, few people use middleware to fetch data at the moment anyway.

Then introducing the middleware PR and add support for it for our loadingIndicator component.

[pi0]

Nothing is blocking if middleware is not concern :) Already plan to locally test and merge for RC.5.