Add option forceRevalidateOnReconnect to hard-revalidate when regaining a network connection

[notuxic]

TLDR

Adds an option forceRevalidateOnReconnect, which when set to true, triggers a revalidation after reconnecting even when dedupingInterval hasn't passed yet. To compensate spotty network connections, an option reconnectThrottleInterval allows to throttle further revalidations for this event.

Background

I'm currently working on an app using SWR with a high dedupingInterval (30 seconds). Depending on network availability, the fetcher fetches data either from network or a local cache.

Now if users navigate to a screen while offline, and then turn on the network (for example because they see the "no-network" placeholder when there's no cached data), the data won't be revalidated since the 30 seconds of the dedupingInterval haven't passed yet.

forceRevalidateOnReconnect

With the new option forceRevalidateOnReconnect set to true (defaulting to false), SWR will call revalidate() instead of softRevalidate() to bypass dedupingInterval, similar to mutate-events.

reconnectThrottleInterval

On spotty network connections, the above new option may trigger a lot of unwanted/unneeded revalidations. For this reason a second option reconnectThrottleInterval allows to throttle revalidations on reconnect-events, similar to the existing focusThrottleInterval for focus-events.

reconnectThrottleInterval defaults to 5000 for consistency with focusThrottleInterval.

Open questions

Default value for reconnectThrottleInterval

Currently reconnectThrottleInterval uses the same default value as focusThrottleInterval for consistency.

A default value of 0 would preserve backwards-compatible behaviour on reconnect-events, but may not be as good of a default for the feature.

Maybe the default value should be even higher, since 5 seconds is quite short in the case of spotty network connections.

[codesandbox-ci[bot]]

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Latest deployment of this branch, based on commit a38d67f47195775cd1fe672488bf984c73df688c:

Sandbox	Source
SWR-Basic	Configuration
SWR-States	Configuration
SWR-Infinite	Configuration
SWR-SSR	Configuration

[notuxic]

ping @shuding @huozhi, requesting review, since it's been a month since opening the PR.