fix: override instance watchers with mounting options watchers

Author: lmiller1990

packages/create-instance/create-instance.js

@@ -73,6 +73,24 @@ export default function createInstance(
 
   // make sure all extends are based on this instance
 
+  if (instanceOptions.watch) {
+    console.log(instanceOptions.watch)
+  }
+
+  // watchers provided in mounting options should override preexisting ones
+  if (componentOptions.watch && instanceOptions.watch) {
+    const componentWatchers = Object.keys(componentOptions.watch)
+    const instanceWatchers = Object.keys(instanceOptions.watch)
+
+    for (let i = 0; i < instanceWatchers.length; i++) {
+      const k = instanceWatchers[i]
+      // override the componentOptions with the one provided in mounting options
+      if (componentWatchers.includes(k)) {
+        componentOptions.watch[k] = instanceOptions.watch[k]
+      }
+    }
+  }
+
   const Constructor = _Vue.extend(componentOptions).extend(instanceOptions)
   componentOptions._Ctor = {}
   Constructor.options._base = _Vue

test/specs/mounting-options/watch.spec.js

@@ -1,21 +1,22 @@
-import {
-  describeWithShallowAndMount,
-  isRunningPhantomJS,
-  vueVersion
-} from '~resources/utils'
+import { describeWithShallowAndMount } from '~resources/utils'
 import { itSkipIf, itDoNotRunIf } from 'conditional-specs'
 
 describeWithShallowAndMount('options.watch', mountingMethod => {
   it('overrides a default watch handler', async () => {
     const TestComponent = {
-      props: ['someProp'],
+      props: ['someProp', 'anotherProp'],
       template: '<div>{{ foo }}</div>',
       data() {
         return {
           foo: 'bar'
         }
       },
       watch: {
+        anotherProp: {
+          handler() {
+            // placeholder
+          }
+        },
         someProp: {
           handler() {
             this.foo = 'updated-bar'