respect default data value for absent Boolean prop (fix vuejs#1020)

Author: yyx990803

src/compiler/compile-props.js

@@ -92,11 +92,14 @@ module.exports = function compileProps (el, propOptions) {
 
 function makePropsLinkFn (props) {
   return function propsLinkFn (vm, el) {
+    // store resolved props info
+    vm._props = {}
     var i = props.length
     var prop, path, options, value
     while (i--) {
       prop = props[i]
       path = prop.path
+      vm._props[path] = prop
       options = prop.options
       if (prop.raw === null) {
         // initialize absent prop

src/instance/compile.js

@@ -182,11 +182,11 @@ exports._cleanup = function () {
   // observing the same object, but that seems to be a
   // reasonable responsibility for the user rather than
   // always throwing an error on them.
-  this._watchers =
   this.$el =
   this.$parent =
   this.$root =
   this.$children =
+  this._watchers =
   this._directives = null
   // call the last hook...
   this._isDestroyed = true

src/instance/scope.js

@@ -53,10 +53,7 @@ exports._initData = function () {
   if (optionsData) {
     this._data = optionsData
     for (var prop in propsData) {
-      if (
-        !optionsData.hasOwnProperty(prop) ||
-        propsData[prop] !== undefined
-      ) {
+      if (this._props[prop].raw !== null) {
         optionsData.$set(prop, propsData[prop])
       }
     }

test/unit/specs/directives/prop_spec.js

@@ -403,5 +403,27 @@ if (_.inBrowser) {
       expect(vm.msg).toBe('hi!')
       expect(el.textContent).toBe('ho!')
     })
+
+    it('should not overwrite default value for an absent Boolean prop', function () {
+      var vm = new Vue({
+        el: el,
+        template: '<test></test>',
+        components: {
+          test: {
+            props: {
+              prop: Boolean
+            },
+            data: function () {
+              return {
+                prop: true
+              }
+            },
+            template: '{{prop}}'
+          }
+        }
+      })
+      expect(vm.$children[0].prop).toBe(true)
+      expect(vm.$el.textContent).toBe('true')
+    })
   })
 }