add failing test: when changing the atom value with onMount setSelf, subscribers are not called

Author: dmaskasky

tests/vanilla/store.test.tsx

@@ -579,3 +579,28 @@ it('should update derived atom even if dependances changed (#2697)', () => {
   store.set(primitiveAtom, 1)
   expect(onChangeDerived).toHaveBeenCalledTimes(1)
 })
+
+it('should call subscribers after setSelf updates atom value', () => {
+  const store = createStore()
+  const a = atom(0)
+  let unmount
+  a.onMount = vi.fn((setSelf) => {
+    setSelf(1)
+    unmount = vi.fn(() => {
+      console.log('onUnmount')
+      setSelf(2)
+    })
+    return unmount
+  })
+  const listener = vi.fn(() => {
+  })
+  const unsub = store.sub(a, listener)
+  expect(store.get(a)).toBe(1)
+  expect(a.onMount).toHaveBeenCalledTimes(1)
+  expect(listener).toHaveBeenCalledTimes(1)
+  listener.mockClear()
+  unsub()
+  expect(store.get(a)).toBe(2)
+  expect(unmount).toHaveBeenCalledTimes(1)
+  expect(listener).toHaveBeenCalledTimes(1)
+})