initialData has no effect if query is in flight

[tannerlinsley]

Prepping for a workshop and wanted to use this paradigm, but it feels broken and we should talk about it:

• https://codesandbox.io/s/agitated-colden-0v0mp?file=/src/index.js
• Hover over item (it will start prefetching, which artificially takes 3 seconds)
• Click on item before prefetching completes
• Post view is shown in the "hard" isLoading state.

Expected:

• Click on item before prefetching completes
• Post view is shown using the initialData (imagine a preview/partial version of the data)
• Full post is loaded as the original fetch from the prefetch call completes

Thoughts?

PS. This is also the behavior in 2.x

[tannerlinsley]

I think this is obviously working exactly how it's designed where if a query is already in flight, it is considered in a loading state from the beginning, which means it won't try and use initialData. I'm wondering how we could model this enhancement though. Maybe something like:

if (isLoading && initialData) {
  // do initial data stuff
}

[boschni]

What if you move the initialData into the prefetch?

[tannerlinsley]

Yeah that’s the current workaround that works. Just a weird location. It would be awesome to be able to just configure the initial data in a single place in my app. Tanner Linsley

…

On Oct 11, 2020, 2:00 AM -0600, Niek Bosch ***@***.***>, wrote: What if you move the initialData into the prefetch? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or unsubscribe.

[tannerlinsley]

This is where i wonder about just using destructured default data instead of initial data. But then it kinda messes with the whole status rendering concept. I would then have to also check if data exists, even though it's in a hard loading state.... Hmmmm

[tannerlinsley]

WHAT IF.... initialData didn't set the cache, but it just overrides the observer state/data.

So in pseudo code:

// observer
if (isLoading && initialData) {
  isSuccess = true
  data = initialData()
}

[tannerlinsley]

I remember there were still reasons to allow initialData to set the data in the cache, so maybe this could even be a new option like placeholderData. 🤷

[sergiodxa]

In SWR, the initial data is local and not saved in the cache, this causes a lot of issues when hydrating from SSR, but with the hydrate feature of RQ this should not be a problem.

[boschni]

Placeholder data has been added