[RTKQ] When using selectFromResult, return the usual properties by default as well

[awdyson]

selectFromResult is a really convenient utility, but it can grow a bit out of hand space-wise.

const { nestedData, isLoading } = useSomething(
  { id: 123 },
  {
    selectFromResult: ({ data, ...rest }) => ({
      nestedData: data.some.annoyingly.deep.data,
      ...rest, // I end up including this in almost every call
    })
  },
);

Assuming it wouldn't cause a significant performance impact, it'd be nice to just include the usual return properties, minus data. So the above could be rewritten like this (showing an ideal space-saving example):

// isLoading still available
const { nestedData, isLoading } = useSomething(
  { id: 123 },
  { selectFromResult: ({ data }) => ({ nestedData: data.some.annoyingly.deep.data }) },
);

[Shrugsy]

Realistically it will have a performance impact. Using selectFromResult has two main benefits:

• Adding/deriving/transforming properties returned by the hook (like getting deep nested data in your example)
• Optimising the hook to only cause a re-render when the 'selected' properties change

For your case, to optimise renders, you should not spread the rest of the properties, but only pass through isLoading from that if it is the only thing you are using. By passing through the rest, you are allowing it to re-render when any of the other properties change which you aren't using (e.g. isFetching, or other parts of the returned data that you aren't reading)

const { nestedData, isLoading } = useSomething(
  { id: 123 },
  {
    selectFromResult: ({ data, ...rest }) => ({
      nestedData: data.some.annoyingly.deep.data,
      isLoading: rest.isLoading
    })
  },
);

If we change it to always return all data by default, then we would also need a way to opt back out of the behaviour to allow for the second dot point above. I imagine that most users would not want to be returning all data and would only want to return the pieces they are using, so I don't see this as being feasible.

[awdyson]

Ah nice, selectFromResult's benefit is grander in scope that I realized.
Appreciate the detailed breakdown.