Be able to delete array item in Vue.delete (#4747)

* Support to delete array item in Vue.delete

* add test case for Vue.delete array

* add blank line between test cases

Author: Hanks10100

Diff for: src/core/observer/index.js

@@ -218,7 +218,11 @@ export function set (obj: Array<any> | Object, key: any, val: any) {
 /**
  * Delete a property and trigger change if necessary.
  */
-export function del (obj: Object, key: string) {
+export function del (obj: Array<any> | Object, key: any) {
+  if (Array.isArray(obj)) {
+    obj.splice(key, 1)
+    return
+  }
   const ob = obj.__ob__
   if (obj._isVue || (ob && ob.vmCount)) {
     process.env.NODE_ENV !== 'production' && warn(

Diff for: test/unit/features/global-api/set-delete.spec.js

@@ -72,5 +72,29 @@ describe('Global API: set/delete', () => {
         expect(vm.$el.innerHTML).toBe('')
       }).then(done)
     })
+
+    it('be able to delete an item in array', done => {
+      const vm = new Vue({
+        template: '<div><p v-for="obj in lists">{{obj.name}}</p></div>',
+        data: {
+          lists: [
+            { name: 'A' },
+            { name: 'B' },
+            { name: 'C' }
+          ]
+        }
+      }).$mount()
+      expect(vm.$el.innerHTML).toBe('<p>A</p><p>B</p><p>C</p>')
+      Vue.delete(vm.lists, 1)
+      waitForUpdate(() => {
+        expect(vm.$el.innerHTML).toBe('<p>A</p><p>C</p>')
+        Vue.delete(vm.lists, 1)
+      }).then(() => {
+        expect(vm.$el.innerHTML).toBe('<p>A</p>')
+        Vue.delete(vm.lists, 0)
+      }).then(() => {
+        expect(vm.$el.innerHTML).toBe('')
+      }).then(done)
+    })
   })
 })