Types for date fields differ in input and output.

[jckw]

The input type is different to the output type for a date field, however the types in functions etc do not reflect this.

E.g.

type Profile = {
  createdAt: Date
}

const { add, data } = useCollection<Profile>('profiles')


add({
  // works and correctly stored as a timestamp in Firestore
  createdAt: new Date()
})

console.log(data[0].createdAt instance Date) // false
// actually an instance of FirestoreTimestamp

Since the type used is the one passed as a the generic Profile, the type of createdAt in data is wrong.

There is also one exception to this rule: if the cache is being used after add. In that case, there will be two potential types being used... since the cached items that are created via add use the Date types, whereas the cached items from firebase have the FirestoreTimestamp type.

This type mismatch also means that sorting does not work correctly.

[nandorojo]

This is due to how firestore handles dates. Use the parseDates field

[nandorojo]

Also, I believe instead of new Date() you should use a Firestore server time stamp, but maybe someone else can confirm that

[jckw]

Aha! I missed parseDates, thank you!

There still the problem of how the cache is organised. It seems unrelated to this issue though, since inserting at the end of the cache is hard-coded into:

swr-firestore/src/hooks/use-swr-collection.ts

Line 520 in 6884464

return [...state, ...docsToAdd]

Perhaps best to move to another issue to discuss how cache updating options can be customised?