Add a global Vue.depTarget api support

flow/global-api.js

@@ -8,6 +8,7 @@ declare interface GlobalAPI {
   set: <T>(target: Object | Array<T>, key: string | number, value: T) => T;
   delete: <T>(target: Object| Array<T>, key: string | number) => void;
   nextTick: (fn: Function, context?: Object) => void | Promise<*>;
+  depTarget: (target: {storage: ?Watcher}) => {storage: ?Watcher} | void;
   use: (plugin: Function | Object) => void;
   mixin: (mixin: Object) => void;
   compile: (template: string) => { render: Function, staticRenderFns: Array<Function> };

src/core/global-api/index.js

@@ -6,6 +6,7 @@ import { initMixin } from './mixin'
 import { initExtend } from './extend'
 import { initAssetRegisters } from './assets'
 import { set, del } from '../observer/index'
+import { depTarget } from '../observer/dep'
 import { ASSET_TYPES } from 'shared/constants'
 import builtInComponents from '../components/index'
 
@@ -43,6 +44,7 @@ export function initGlobalAPI (Vue: GlobalAPI) {
   Vue.set = set
   Vue.delete = del
   Vue.nextTick = nextTick
+  Vue.depTarget = depTarget
 
   Vue.options = Object.create(null)
   ASSET_TYPES.forEach(type => {

src/core/observer/dep.js

@@ -10,7 +10,7 @@ let uid = 0
  * directives subscribing to it.
  */
 export default class Dep {
-  static target: ?Watcher;
+  static target: {storage: ?Watcher};
   id: number;
   subs: Array<Watcher>;
 
@@ -28,8 +28,8 @@ export default class Dep {
   }
 
   depend () {
-    if (Dep.target) {
-      Dep.target.addDep(this)
+    if (Dep.target.storage) {
+      Dep.target.storage.addDep(this)
     }
   }
 
@@ -45,14 +45,24 @@ export default class Dep {
 // the current target watcher being evaluated.
 // this is globally unique because there could be only one
 // watcher being evaluated at any time.
-Dep.target = null
+Dep.target = {
+  storage: null
+}
 const targetStack = []
 
 export function pushTarget (_target: ?Watcher) {
-  if (Dep.target) targetStack.push(Dep.target)
-  Dep.target = _target
+  if (Dep.target.storage) targetStack.push(Dep.target.storage)
+  Dep.target.storage = _target
 }
 
 export function popTarget () {
-  Dep.target = targetStack.pop()
+  Dep.target.storage = targetStack.pop()
+}
+
+export function depTarget (target: {storage: ?Watcher}): {storage: ?Watcher} | void {
+  if (target) {
+    Dep.target = target
+  } else {
+    return Dep.target
+  }
 }

src/core/observer/index.js

@@ -158,7 +158,7 @@ export function defineReactive (
     configurable: true,
     get: function reactiveGetter () {
       const value = getter ? getter.call(obj) : val
-      if (Dep.target) {
+      if (Dep.target.storage) {
         dep.depend()
         if (childOb) {
           childOb.dep.depend()

src/core/observer/watcher.js

@@ -243,7 +243,7 @@ export default class Watcher {
    * Depend on this watcher. Only for computed property watchers.
    */
   depend () {
-    if (this.dep && Dep.target) {
+    if (this.dep && Dep.target.storage) {
       this.dep.depend()
     }
   }

test/unit/modules/observer/dep.spec.js

@@ -34,22 +34,22 @@ describe('Dep', () => {
     let _target
 
     beforeAll(() => {
-      _target = Dep.target
+      _target = Dep.target.storage
     })
 
     afterAll(() => {
-      Dep.target = _target
+      Dep.target.storage = _target
     })
 
     it('should do nothing if no target', () => {
-      Dep.target = null
+      Dep.target.storage = null
       dep.depend()
     })
 
     it('should add itself to target', () => {
-      Dep.target = jasmine.createSpyObj('TARGET', ['addDep'])
+      Dep.target.storage = jasmine.createSpyObj('TARGET', ['addDep'])
       dep.depend()
-      expect(Dep.target.addDep).toHaveBeenCalledWith(dep)
+      expect(Dep.target.storage.addDep).toHaveBeenCalledWith(dep)
     })
   })
 

test/unit/modules/observer/observer.spec.js

@@ -189,9 +189,9 @@ describe('Observer', () => {
       update: jasmine.createSpy()
     }
     // collect dep
-    Dep.target = watcher
+    Dep.target.storage = watcher
     obj.a.b
-    Dep.target = null
+    Dep.target.storage = null
     expect(watcher.deps.length).toBe(3) // obj.a + a + a.b
     obj.a.b = 3
     expect(watcher.update.calls.count()).toBe(1)
@@ -200,10 +200,10 @@ describe('Observer', () => {
     expect(watcher.update.calls.count()).toBe(2)
     watcher.deps = []
 
-    Dep.target = watcher
+    Dep.target.storage = watcher
     obj.a.b
     obj.c
-    Dep.target = null
+    Dep.target.storage = null
     expect(watcher.deps.length).toBe(4)
     // set on the swapped object
     obj.a.b = 5
@@ -236,9 +236,9 @@ describe('Observer', () => {
       update: jasmine.createSpy()
     }
     // collect dep
-    Dep.target = watcher
+    Dep.target.storage = watcher
     expect(obj.a).toBe(2) // Make sure 'this' is preserved
-    Dep.target = null
+    Dep.target.storage = null
     obj.a = 3
     expect(obj.val).toBe(3) // make sure 'setter' was called
     obj.val = 5