Add a placeholder data option

[minht11]

Loading spinners are bad, it less disruptive to show users previous data until new data is ready. Suspense is somewhat based on that idea.

Have code like this:

const { data } = useQuery({
    key: () => ['item', props.selectedItemId],
    query: () => getItemById(props.selectedItemId),
})

when props.selectedItemId changes current behavior of useQuery forces me to show blank screen because data does not exist, I wish data would not be reset while isFetching is true.

[posva]

It’s normal it’s not kept by default. But maybe a placeholder option could add this

Notes:

• It should allow a function placeholderData: (previousData) => Data
• Must be sync
• Must be compatible in type with the regular data
• Should set the status to success
• Need a way to transfer this piece of info during SSR to avoid using a placeholder data as initial data
• should not be used in the cache as data, only be a fallback