refactor: tweak data merge strategy (vuejs#6833)

HcySunYang · 孙广彪 · commit c33955f70a8d · 2017-12-15T16:09:58.000+08:00
* tweak: The value of this is always undefined

* parentVal and childVal must have a presence, otherwise the strats.data policy function will not be executed
diff --git a/src/core/util/options.js b/src/core/util/options.js
@@ -100,7 +100,7 @@ export function mergeDataOrFn (
         typeof parentVal === 'function' ? parentVal.call(this) : parentVal
       )
     }
-  } else if (parentVal || childVal) {
+  } else {
     return function mergedInstanceDataFn () {
       // instance merge
       const instanceData = typeof childVal === 'function'
@@ -134,7 +134,7 @@ strats.data = function (
 
       return parentVal
     }
-    return mergeDataOrFn.call(this, parentVal, childVal)
+    return mergeDataOrFn(parentVal, childVal)
   }
 
   return mergeDataOrFn(parentVal, childVal, vm)

Original file line number	Diff line number	Diff line change
`@@ -100,7 +100,7 @@ export function mergeDataOrFn (`
`100`	`100`	`typeof parentVal === 'function' ? parentVal.call(this) : parentVal`
`101`	`101`	`)`
`102`	`102`	`}`
`103`		`- } else if (parentVal \|\| childVal) {`
	`103`	`+ } else {`
`104`	`104`	`return function mergedInstanceDataFn () {`
`105`	`105`	`// instance merge`
`106`	`106`	`const instanceData = typeof childVal === 'function'`
`@@ -134,7 +134,7 @@ strats.data = function (`
`134`	`134`
`135`	`135`	`return parentVal`
`136`	`136`	`}`
`137`		`- return mergeDataOrFn.call(this, parentVal, childVal)`
	`137`	`+ return mergeDataOrFn(parentVal, childVal)`
`138`	`138`	`}`
`139`	`139`
`140`	`140`	`return mergeDataOrFn(parentVal, childVal, vm)`