Suspense mode with useTransition mutate not work expectly

[xiaoxiyao]

Bug report

Description / Observed Behavior

Pending state flashed briefly, expected to persist for 1 second.

Repro Steps / Code Example

https://codesandbox.io/p/sandbox/swr-suspense-wrzxgn

Additional Context

SWR version: 2.3.3

[angeeeeelh]

Hello @xiaoxiyao,
I do not see a bug with SWR. The way this code is using SWR and React hooks is behaving as I expect.

1. The code is using React version 18.x.x, which means the "useTransition" hook requires synchronous updates
2. I also don't recommend mutate being used with useTransition for what I think you want. SWR will not allow you to mock a delayed fetching of data easily because it's supposed to fetch (cached or new) data fast.

Here's code I wrote of what I think you're looking for.

[xiaoxiyao]

Thanks @angeeeeelh , initially I wanted to wrap mutate with useTransition to avoid triggering suspense repeatedly. Later, I realized that mutate does not trigger suspense, and I can directly use isValidating to determine whether data is being re-fetched.

I wonder if this means that SWR's suspense mode only triggers suspense during the initial data fetch, and subsequent mutate or revalidation is always a "transition". Therefore, SWR neither needs nor can work with useTransition.