fix: Vue.config.errorHandler should capture rejected promised in watchers(vuejs#10009)

Author: underfin

src/core/observer/watcher.js

@@ -7,6 +7,7 @@ import {
   parsePath,
   _Set as Set,
   handleError,
+  invokeWithErrorHandling,
   noop
 } from '../util/index'
 
@@ -191,11 +192,7 @@ export default class Watcher {
         const oldValue = this.value
         this.value = value
         if (this.user) {
-          try {
-            this.cb.call(this.vm, value, oldValue)
-          } catch (e) {
-            handleError(e, this.vm, `callback for watcher "${this.expression}"`)
-          }
+          invokeWithErrorHandling(this.cb, this.vm, [value, oldValue], this.vm, ("callback for watcher \"" + (this.expression) + "\""))
         } else {
           this.cb.call(this.vm, value, oldValue)
         }

test/unit/features/error-handling.spec.js

@@ -138,6 +138,16 @@ describe('Error handling', () => {
     }).then(done)
   })
 
+  it('should recover from errors in user watcher from promise error', done => {
+    const vm = createTestInstance(components.userWatcherPromise)
+    vm.n++
+    setTimeout(() => {
+      expect(`Error in callback for watcher "n" (Promise/async)`).toHaveBeenWarned()
+      expect(`Error: userWatcherPromise error`).toHaveBeenWarned()
+      assertBothInstancesActive(vm).then(done)
+    })
+  })
+
   it('should recover from errors in user immediate watcher callback', done => {
     const vm = createTestInstance(components.userImmediateWatcherCallback)
     waitForUpdate(() => {
@@ -344,6 +354,18 @@ function createErrorTestComponents () {
     }
   }
 
+  components.userWatcherPromise = {
+    props: ['n'],
+    watch: {
+      n () {
+        return new Promise((resolve, reject) => reject(new Error('userWatcherPromise error')))
+      }
+    },
+    render (h) {
+      return h('div', this.n)
+    }
+  }
+
   components.userImmediateWatcherCallback = {
     props: ['n'],
     watch: {