Hello,

I found a minor issue in the useMemoSelector implementation in Zustand v5.0.0-alpha.1. Here's the code:

const useMemoSelector = <TState, StateSlice>(
  getState: () => TState,
  selector: (state: TState) => StateSlice,
) =>
  useMemo(() => {
    let lastSlice: StateSlice
    let lastState: TState
    return () => {
      const state = getState()
      if (!Object.is(lastState, state)) {
        lastSlice = selector(state)
        lastState = state
      }
      return lastSlice
    }
  }, [getState, selector])

Do you notice the subtle issue? It's that when the state is initially undefined, the selector function isn't called, although it should be. This situation is rare because most use cases use object states. It's not well-known that Zustand supports primitive values. Even with primitive values, it's very unlikely they are undefined. Nonetheless, as a library, it should behave correctly. Library development is a little different from app development from this perspective.

Happy Hacking.

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