Match-id-78aab772cb8e654ef883d9b69084d2c4da273119

libs/horizon/src/renderer/diff/nodeDiffComparator.ts

@@ -294,8 +294,9 @@ function diffArrayNodesHandler(
       if (rightOldIndex < 0 || rightOldNode === null) {
         break;
       }
-
+      // 新旧节点的index应该相同才能复用，null会影响位置
-      canBeReuse = checkCanReuseNode(rightOldNode, newChildren[rightIdx - 1]);
+      const samePosition = rightOldNode.eIndex === rightIdx - 1;
+      canBeReuse = checkCanReuseNode(rightOldNode, newChildren[rightIdx - 1]) && samePosition;
       // 不能复用，break
       if (!canBeReuse) {
         break;

scripts/__tests__/ComponentTest/DiffAlgorithm.test.js

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) Huawei Technologies Co., Ltd. 2022-2022. All rights reserved.
+ */
+
+import * as Horizon from '@cloudsop/horizon/index.ts';
+
+describe('Diff Algorithm', () => {
+  it('null should diff correctly', () => {
+    const fn = jest.fn();
+
+    class C extends Horizon.Component {
+      constructor() {
+        super();
+        fn();
+      }
+
+      render() {
+        return 1;
+      }
+    }
+
+    let update;
+
+    function App() {
+      const [current, setCurrent] = Horizon.useState(1);
+      update = setCurrent;
+      return (
+        <>
+          {current === 1 ? <C /> : null}
+          {current === 2 ? <C /> : null}
+          {current === 3 ? <C /> : null}
+        </>
+      );
+    }
+
+    Horizon.render(<App text="app" />, container);
+    expect(fn).toHaveBeenCalledTimes(1);
+
+    update(2);
+    expect(fn).toHaveBeenCalledTimes(2);
+
+    update(3);
+    expect(fn).toHaveBeenCalledTimes(3);
+
+    update(1);
+    expect(fn).toHaveBeenCalledTimes(4);
+  });
+});

scripts/__tests__/ComponentTest/HookTest/UseEffect.test.js

@@ -81,7 +81,7 @@ describe('useEffect Hook Test', () => {
     expect(LogUtils.getAndClear()).toEqual([]);
     // 在执行新的render前，会执行完上一次render的useEffect，所以LogUtils会加入'NewApp effect'。
     Horizon.render([na], container);
-    expect(LogUtils.getAndClear()).toEqual(['NewApp effect']);
+    expect(LogUtils.getAndClear()).toEqual(['NewApp effect', 'NewApp']);
     expect(container.textContent).toBe('NewApp');
     expect(LogUtils.getAndClear()).toEqual([]);
   });