[docs] conditional fetching and dedupingInterval

[Izhaki]

We are surveying using swr as our data-fetching technology (so far it looks amazing).

Even after reading the documentation, we still had some questions.

We know the answers for the questions below (it is easy to run a quick experiment to get the answers), but possibly the documentation can be updated to prevent us having to run experiments.

Conditional Fetching

The docs give this example:

// conditionally fetch
const { data } = useSWR(shouldFetch ? '/api/data' : null, fetcher)

Our case:

const shouldFetch = !doNotDisturb; // User can toggle this at will (this is fictional condition, but demonstrate something that can change dynamically).
const { data } = useSWR(shouldFetch ? '/api/data' : null, fetcher, { refreshInterval: MINUTE });

Question is: If shouldFetch toggles from true to false, polling will stop right (and then restart when it toggles back to true)?

dedupingInterval

Our use case is this:

• We want to poll every minute.
• Other than polling we always want to dedup (there could be multiple requests by the user that will have the same swr key - we want them all served from cache).

We are not sure how these two interact.

Say our configuration is like so:

{
  refreshInterval: 5 * MINUTES,
  dedupingInterval: 6 * MINUTES,
}

Question are:

• Will it poll after 5 minutes (or will the dedupe serve from cache)?
• If there is a poll after 5 minutes, and the user trigger a request after 7 minutes that is already cached, will dedupe kick in (or does it reset with polling).

---

On a separate note, we found the term dedupingInterval a bit confusing. Dedupe typically means removing duplicate items from a list. Maybe from an implementation point of view this is what's happening. But for users, why not just call it cacheInterval?

There's farther confusion between the caching and deep-compare - if either the cache is served or the returned value is the same, data will not be mutated. Which does dedupingInterval control?