adjust sameVnode check (fix #3176)

Author: yyx990803

src/core/vdom/patch.js

@@ -23,7 +23,11 @@ function isDef (s) {
 }
 
 function sameVnode (vnode1, vnode2) {
-  return vnode1.key === vnode2.key && vnode1.tag === vnode2.tag
+  return (
+    vnode1.key === vnode2.key &&
+    vnode1.tag === vnode2.tag &&
+    !vnode1.data === !vnode2.data
+  )
 }
 
 function createKeyToOldIdx (children, beginIdx, endIdx) {
@@ -269,12 +273,8 @@ export function createPatchFunction (backend) {
     if (oldVnode === vnode) return
     let i, hook
     const hasData = isDef(i = vnode.data)
-    if (hasData) {
-      // ensure the oldVnode also has data during patch
-      oldVnode.data = oldVnode.data || emptyData
-      if (isDef(hook = i.hook) && isDef(i = hook.prepatch)) {
-        i(oldVnode, vnode)
-      }
+    if (hasData && isDef(hook = i.hook) && isDef(i = hook.prepatch)) {
+      i(oldVnode, vnode)
     }
     const elm = vnode.elm = oldVnode.elm
     const oldCh = oldVnode.children

test/unit/modules/vdom/patch/children.spec.js

@@ -450,4 +450,20 @@ describe('children', () => {
     expect(map(tag, elm.children)).toEqual(['DIV', 'SPAN', 'SPAN', 'DIV'])
     expect(map(inner, elm.children)).toEqual(['four', 'three', 'two', 'one'])
   })
+
+  it('should handle children with the same tag, same key, but one with data and one without data', () => {
+    const vnode1 = new VNode('div', {}, [
+      new VNode('div', { class: 'hi' }, undefined, 'one')
+    ])
+    const vnode2 = new VNode('div', {}, [
+      new VNode('div', undefined, undefined, 'four')
+    ])
+    let elm = patch(vnode0, vnode1)
+    const child1 = elm.children[0]
+    expect(child1.className).toBe('hi')
+    elm = patch(vnode1, vnode2)
+    const child2 = elm.children[0]
+    expect(child1).not.toBe(child2)
+    expect(child2.className).toBe('')
+  })
 })

test/unit/modules/vdom/patch/hooks.spec.js

@@ -242,7 +242,7 @@ describe('hooks', () => {
         new VNode('span', {}, undefined, 'child 2')
       ])
     ])
-    const vnode2 = new VNode('div')
+    const vnode2 = new VNode('div', {})
     patch1(vnode0, vnode1)
     expect(destroyed).toBe(1) // should invoke for replaced root nodes too
     patch1(vnode1, vnode2)
@@ -265,7 +265,7 @@ describe('hooks', () => {
       createTextVNode(''),
       new VNode('span', {}, undefined, 'third child')
     ])
-    const vnode2 = new VNode('div')
+    const vnode2 = new VNode('div', {})
     patch1(vnode0, vnode1)
     patch1(vnode1, vnode2)
     expect(created).toBe(3)
@@ -292,7 +292,7 @@ describe('hooks', () => {
         ])
       ])
     ])
-    const vnode2 = new VNode('div')
+    const vnode2 = new VNode('div', {})
     patch1(vnode0, vnode1)
     expect(destroyed).toBe(1) // should invoke for replaced root nodes too
     patch1(vnode1, vnode2)