fix(runtime-core): should not track deps in pre flush watcher callbacks

fix #2728

packages/runtime-core/__tests__/apiWatch.spec.ts

@@ -877,4 +877,42 @@ describe('api: watch', () => {
  expect(instance).toBeDefined()
  expect(source).toHaveBeenCalledWith(instance)
  })
+
+ // #2728
+ test('pre watcher callbacks should not track dependencies', async () => {
+ const a = ref(0)
+ const b = ref(0)
+ const updated = jest.fn()
+
+ const Child = defineComponent({
+ props: ['a'],
+ updated,
+ watch: {
+ a() {
+ b.value
+ }
+ },
+ render() {
+ return h('div', this.a)
+ }
+ })
+
+ const Parent = defineComponent({
+ render() {
+ return h(Child, { a: a.value })
+ }
+ })
+
+ const root = nodeOps.createElement('div')
+ createApp(Parent).mount(root)
+
+ a.value++
+ await nextTick()
+ expect(updated).toHaveBeenCalledTimes(1)
+
+ b.value++
+ await nextTick()
+ // should not track b as dependency of Child
+ expect(updated).toHaveBeenCalledTimes(1)
+ })
 })

packages/runtime-core/src/renderer.ts

@@ -48,7 +48,14 @@ import {
  flushPreFlushCbs,
  SchedulerCb
 } from './scheduler'
-import { effect, stop, ReactiveEffectOptions, isRef } from '@vue/reactivity'
+import {
+ effect,
+ stop,
+ ReactiveEffectOptions,
+ isRef,
+ pauseTracking,
+ resetTracking
+} from '@vue/reactivity'
 import { updateProps } from './componentProps'
 import { updateSlots } from './componentSlots'
 import { pushWarningContext, popWarningContext, warn } from './warning'
@@ -1567,9 +1574,11 @@ function baseCreateRenderer(
  updateProps(instance, nextVNode.props, prevProps, optimized)
  updateSlots(instance, nextVNode.children)
 
+ pauseTracking()
  // props update may have triggered pre-flush watchers.
  // flush them before the render update.
  flushPreFlushCbs(undefined, instance.update)
+ resetTracking()
  }
 
  const patchChildren: PatchChildrenFn = (