Don't re-run the selector after update (#1701)

Author: timdorr

src/hooks/useSelector.js

@@ -64,13 +64,15 @@ function useSelectorWithStoreAndSubscription(
   useIsomorphicLayoutEffect(() => {
     function checkForUpdates() {
       try {
-        const newSelectedState = latestSelector.current(store.getState())
+        const newStoreState = store.getState()
+        const newSelectedState = latestSelector.current(newStoreState)
 
         if (equalityFn(newSelectedState, latestSelectedState.current)) {
           return
         }
 
         latestSelectedState.current = newSelectedState
+        latestStoreState.current = newStoreState
       } catch (err) {
         // we ignore all errors here, since when the component
         // is re-rendered, the selectors are called again, and

test/hooks/useSelector.spec.js

@@ -38,17 +38,21 @@ describe('React', () => {
         })
 
         it('selects the state and renders the component when the store updates', () => {
-          const { result } = renderHook(() => useSelector((s) => s.count), {
+          const selector = jest.fn((s) => s.count)
+
+          const { result } = renderHook(() => useSelector(selector), {
             wrapper: (props) => <ProviderMock {...props} store={store} />,
           })
 
           expect(result.current).toEqual(0)
+          expect(selector).toHaveBeenCalledTimes(2)
 
           act(() => {
             store.dispatch({ type: '' })
           })
 
           expect(result.current).toEqual(1)
+          expect(selector).toHaveBeenCalledTimes(3)
         })
       })