fix(data): skip recursive call if values are identical (vuejs#8967)

KaelWD · hefeng · commit 941b9ac1d49c · 2019-01-25T17:44:21.000+08:00
diff --git a/src/core/util/options.js b/src/core/util/options.js
@@ -55,7 +55,11 @@ function mergeData (to: Object, from: ?Object): Object {
     fromVal = from[key]
     if (!hasOwn(to, key)) {
       set(to, key, fromVal)
-    } else if (isPlainObject(toVal) && isPlainObject(fromVal)) {
+    } else if (
+      toVal !== fromVal &&
+      isPlainObject(toVal) &&
+      isPlainObject(fromVal)
+    ) {
       mergeData(toVal, fromVal)
     }
   }

Original file line number	Diff line number	Diff line change
`@@ -55,7 +55,11 @@ function mergeData (to: Object, from: ?Object): Object {`
`55`	`55`	`fromVal = from[key]`
`56`	`56`	`if (!hasOwn(to, key)) {`
`57`	`57`	`set(to, key, fromVal)`
`58`		`- } else if (isPlainObject(toVal) && isPlainObject(fromVal)) {`
	`58`	`+ } else if (`
	`59`	`+ toVal !== fromVal &&`
	`60`	`+ isPlainObject(toVal) &&`
	`61`	`+ isPlainObject(fromVal)`
	`62`	`+ ) {`
`59`	`63`	`mergeData(toVal, fromVal)`
`60`	`64`	`}`
`61`	`65`	`}`