Bug: Suspense Data undefined Race Condition

[jcarroll2007]

I'm not sure if this is a bug, or if this behavior is intended, but I was running into an issue with the line of code below.

So, I'm using useSWR(/api/users/${id}, fetch, {suspense: true}) where the key is dynamic based on the id of the object I want to get (in this contrived example the user's id).

My code looks something like this exampled:

function useUser(id) {
  const user = useSWR(`/api/users/${id}`, fetch, {suspense: true})
  console.log(user)
  return user
}

When this hook is called multiple times with different IDs, the logs would look like this:

// render 1 with user id 1
{ id:1 }
// render 2 with user id 2
undefined
// render 3
{ id: 2 }

The reason behind this is the two LOC referenced below.

So, my question is, in render 2 on L342 typeof data = Object, not undefined because the data is reset on line 358 (afterwards). Should there be a line before line 342 that checks to see if the keyRef.current and the new key are then different and reset data there so that the revalidate can happen immediately?

I quickly implemented this locally and this fixed my issue and prevented render 2 happening where the data was undefined.

Thanks! Loving this library so far.

https://github.com/zeit/swr/blob/9b51b7d066335d7249d114e2b9a2cb5d633795b6/src/use-swr.ts#L342
https://github.com/zeit/swr/blob/9b51b7d066335d7249d114e2b9a2cb5d633795b6/src/use-swr.ts#L358

[shuding]

This is indeed a good optimization. Thank you @jcarroll2007 so much!

[jcarroll2007]

Awesome! Thanks for responding so quickly! Really excited about this hook.