fix(vanilla): bail out notifying with same values (v2 API)

src/vanilla/store.ts

@@ -528,7 +528,21 @@ export const createStore = () => {
             mountDependencies(atom, atomState, prevAtomState?.d)
           }
           const mounted = mountedMap.get(atom)
-          mounted?.l.forEach((listener) => listener())
+          if (
+            mounted &&
+            !(
+              // TODO This seems pretty hacky. Hope to fix it.
+              // Maybe we could `mountDependencies` in `setAtomState`?
+              (
+                prevAtomState &&
+                !hasPromiseAtomValue(prevAtomState) &&
+                (isEqualAtomValue(prevAtomState, atomState) ||
+                  isEqualAtomError(prevAtomState, atomState))
+              )
+            )
+          ) {
+            mounted.l.forEach((listener) => listener())
+          }
         } else if (__DEV__) {
           console.warn('[Bug] no atom state to flush')
         }

tests/vanilla/store.test.tsx

@@ -0,0 +1,22 @@
+import { atom, createStore } from 'jotai/vanilla'
+
+it('should not fire subscription if primitive atom value is the same', async () => {
+  const store = createStore()
+  const countAtom = atom(0)
+  const callback = jest.fn()
+  store.sub(countAtom, callback)
+  const calledTimes = callback.mock.calls.length
+  store.set(countAtom, 0)
+  expect(callback).toBeCalledTimes(calledTimes)
+})
+
+it('should not fire subscription if derived atom value is the same', async () => {
+  const store = createStore()
+  const countAtom = atom(0)
+  const derivedAtom = atom((get) => get(countAtom) * 0)
+  const callback = jest.fn()
+  store.sub(derivedAtom, callback)
+  const calledTimes = callback.mock.calls.length
+  store.set(countAtom, 1)
+  expect(callback).toBeCalledTimes(calledTimes)
+})