fix(watch): flush:pre watchers should not fire if state change causes

owner component to unmount

fix #2291

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

@@ -509,7 +509,8 @@ describe('api: watch', () => {
     expect(cb).not.toHaveBeenCalled()
   })
 
-  it('should fire on component unmount w/ flush: pre', async () => {
+  // #2291
+  it('should not fire on component unmount w/ flush: pre', async () => {
     const toggle = ref(true)
     const cb = jest.fn()
     const Comp = {
@@ -527,7 +528,7 @@ describe('api: watch', () => {
     expect(cb).not.toHaveBeenCalled()
     toggle.value = false
     await nextTick()
-    expect(cb).toHaveBeenCalledTimes(1)
+    expect(cb).not.toHaveBeenCalled()
   })
 
   // #1763

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

@@ -3,9 +3,8 @@ import {
   nextTick,
   queuePostFlushCb,
   invalidateJob,
-  queuePreFlushCb,
-  flushPreFlushCbs,
-  flushPostFlushCbs
+  flushPostFlushCbs,
+  flushPreFlushCbs
 } from '../src/scheduler'
 
 describe('scheduler', () => {
@@ -114,65 +113,7 @@ describe('scheduler', () => {
     })
   })
 
-  describe('queuePreFlushCb', () => {
-    it('basic usage', async () => {
-      const calls: string[] = []
-      const cb1 = () => {
-        calls.push('cb1')
-      }
-      const cb2 = () => {
-        calls.push('cb2')
-      }
-
-      queuePreFlushCb(cb1)
-      queuePreFlushCb(cb2)
-
-      expect(calls).toEqual([])
-      await nextTick()
-      expect(calls).toEqual(['cb1', 'cb2'])
-    })
-
-    it('should dedupe queued preFlushCb', async () => {
-      const calls: string[] = []
-      const cb1 = () => {
-        calls.push('cb1')
-      }
-      const cb2 = () => {
-        calls.push('cb2')
-      }
-      const cb3 = () => {
-        calls.push('cb3')
-      }
-
-      queuePreFlushCb(cb1)
-      queuePreFlushCb(cb2)
-      queuePreFlushCb(cb1)
-      queuePreFlushCb(cb2)
-      queuePreFlushCb(cb3)
-
-      expect(calls).toEqual([])
-      await nextTick()
-      expect(calls).toEqual(['cb1', 'cb2', 'cb3'])
-    })
-
-    it('chained queuePreFlushCb', async () => {
-      const calls: string[] = []
-      const cb1 = () => {
-        calls.push('cb1')
-        // cb2 will be executed after cb1 at the same tick
-        queuePreFlushCb(cb2)
-      }
-      const cb2 = () => {
-        calls.push('cb2')
-      }
-      queuePreFlushCb(cb1)
-
-      await nextTick()
-      expect(calls).toEqual(['cb1', 'cb2'])
-    })
-  })
-
-  describe('queueJob w/ queuePreFlushCb', () => {
+  describe('pre flush jobs', () => {
     it('queueJob inside preFlushCb', async () => {
       const calls: string[] = []
       const job1 = () => {
@@ -183,8 +124,9 @@ describe('scheduler', () => {
         calls.push('cb1')
         queueJob(job1)
       }
+      cb1.pre = true
 
-      queuePreFlushCb(cb1)
+      queueJob(cb1)
       await nextTick()
       expect(calls).toEqual(['cb1', 'job1'])
     })
@@ -194,17 +136,23 @@ describe('scheduler', () => {
       const job1 = () => {
         calls.push('job1')
       }
+      job1.id = 1
+
       const cb1 = () => {
         calls.push('cb1')
         queueJob(job1)
         // cb2 should execute before the job
-        queuePreFlushCb(cb2)
+        queueJob(cb2)
       }
+      cb1.pre = true
+
       const cb2 = () => {
         calls.push('cb2')
       }
+      cb2.pre = true
+      cb2.id = 1
 
-      queuePreFlushCb(cb1)
+      queueJob(cb1)
       await nextTick()
       expect(calls).toEqual(['cb1', 'cb2', 'job1'])
     })
@@ -216,19 +164,21 @@ describe('scheduler', () => {
         // when updating the props of a child component. This is handled
         // directly inside `updateComponentPreRender` to avoid non atomic
         // cb triggers (#1763)
-        queuePreFlushCb(cb1)
-        queuePreFlushCb(cb2)
-        flushPreFlushCbs(undefined, job1)
+        queueJob(cb1)
+        queueJob(cb2)
+        flushPreFlushCbs()
         calls.push('job1')
       }
       const cb1 = () => {
         calls.push('cb1')
         // a cb triggers its parent job, which should be skipped
         queueJob(job1)
       }
+      cb1.pre = true
       const cb2 = () => {
         calls.push('cb2')
       }
+      cb2.pre = true
 
       queueJob(job1)
       await nextTick()
@@ -237,12 +187,14 @@ describe('scheduler', () => {
 
     // #3806
     it('queue preFlushCb inside postFlushCb', async () => {
-      const cb = jest.fn()
+      const spy = jest.fn()
+      const cb = () => spy()
+      cb.pre = true
       queuePostFlushCb(() => {
-        queuePreFlushCb(cb)
+        queueJob(cb)
       })
       await nextTick()
-      expect(cb).toHaveBeenCalled()
+      expect(spy).toHaveBeenCalled()
     })
   })
 

packages/runtime-core/src/apiWatch.ts

@@ -9,7 +9,7 @@ import {
   EffectScheduler,
   DebuggerOptions
 } from '@vue/reactivity'
-import { SchedulerJob, queuePreFlushCb } from './scheduler'
+import { SchedulerJob, queueJob } from './scheduler'
 import {
   EMPTY_OBJ,
   isObject,
@@ -345,7 +345,9 @@ function doWatch(
     scheduler = () => queuePostRenderEffect(job, instance && instance.suspense)
   } else {
     // default: 'pre'
-    scheduler = () => queuePreFlushCb(job)
+    job.pre = true
+    if (instance) job.id = instance.uid
+    scheduler = () => queueJob(job)
   }
 
   const effect = new ReactiveEffect(getter, scheduler)

packages/runtime-core/src/renderer.ts

@@ -1590,7 +1590,7 @@ function baseCreateRenderer(
     pauseTracking()
     // props update may have triggered pre-flush watchers.
     // flush them before the render update.
-    flushPreFlushCbs(undefined, instance.update)
+    flushPreFlushCbs()
     resetTracking()
   }
 
@@ -2331,6 +2331,7 @@ function baseCreateRenderer(
     } else {
       patch(container._vnode || null, vnode, container, null, null, null, isSVG)
     }
+    flushPreFlushCbs()
     flushPostFlushCbs()
     container._vnode = vnode
   }

packages/runtime-core/src/scheduler.ts

@@ -5,6 +5,7 @@ import { warn } from './warning'
 
 export interface SchedulerJob extends Function {
   id?: number
+  pre?: boolean
   active?: boolean
   computed?: boolean
   /**
@@ -39,19 +40,13 @@ let isFlushPending = false
 const queue: SchedulerJob[] = []
 let flushIndex = 0
 
-const pendingPreFlushCbs: SchedulerJob[] = []
-let activePreFlushCbs: SchedulerJob[] | null = null
-let preFlushIndex = 0
-
 const pendingPostFlushCbs: SchedulerJob[] = []
 let activePostFlushCbs: SchedulerJob[] | null = null
 let postFlushIndex = 0
 
 const resolvedPromise = /*#__PURE__*/ Promise.resolve() as Promise<any>
 let currentFlushPromise: Promise<void> | null = null
 
-let currentPreFlushParentJob: SchedulerJob | null = null
-
 const RECURSION_LIMIT = 100
 type CountMap = Map<SchedulerJob, number>
 
@@ -89,12 +84,11 @@ export function queueJob(job: SchedulerJob) {
   // allow it recursively trigger itself - it is the user's responsibility to
   // ensure it doesn't end up in an infinite loop.
   if (
-    (!queue.length ||
-      !queue.includes(
-        job,
-        isFlushing && job.allowRecurse ? flushIndex + 1 : flushIndex
-      )) &&
-    job !== currentPreFlushParentJob
+    !queue.length ||
+    !queue.includes(
+      job,
+      isFlushing && job.allowRecurse ? flushIndex + 1 : flushIndex
+    )
   ) {
     if (job.id == null) {
       queue.push(job)
@@ -119,71 +113,44 @@ export function invalidateJob(job: SchedulerJob) {
   }
 }
 
-function queueCb(
-  cb: SchedulerJobs,
-  activeQueue: SchedulerJob[] | null,
-  pendingQueue: SchedulerJob[],
-  index: number
-) {
+export function queuePostFlushCb(cb: SchedulerJobs) {
   if (!isArray(cb)) {
     if (
-      !activeQueue ||
-      !activeQueue.includes(cb, cb.allowRecurse ? index + 1 : index)
+      !activePostFlushCbs ||
+      !activePostFlushCbs.includes(
+        cb,
+        cb.allowRecurse ? postFlushIndex + 1 : postFlushIndex
+      )
     ) {
-      pendingQueue.push(cb)
+      pendingPostFlushCbs.push(cb)
     }
   } else {
     // if cb is an array, it is a component lifecycle hook which can only be
     // triggered by a job, which is already deduped in the main queue, so
     // we can skip duplicate check here to improve perf
-    pendingQueue.push(...cb)
+    pendingPostFlushCbs.push(...cb)
   }
   queueFlush()
 }
 
-export function queuePreFlushCb(cb: SchedulerJob) {
-  queueCb(cb, activePreFlushCbs, pendingPreFlushCbs, preFlushIndex)
-}
-
-export function queuePostFlushCb(cb: SchedulerJobs) {
-  queueCb(cb, activePostFlushCbs, pendingPostFlushCbs, postFlushIndex)
-}
-
-export function flushPreFlushCbs(
-  seen?: CountMap,
-  parentJob: SchedulerJob | null = null
-) {
-  if (pendingPreFlushCbs.length) {
-    currentPreFlushParentJob = parentJob
-    activePreFlushCbs = [...new Set(pendingPreFlushCbs)]
-    pendingPreFlushCbs.length = 0
-    if (__DEV__) {
-      seen = seen || new Map()
-    }
-    for (
-      preFlushIndex = 0;
-      preFlushIndex < activePreFlushCbs.length;
-      preFlushIndex++
-    ) {
-      if (
-        __DEV__ &&
-        checkRecursiveUpdates(seen!, activePreFlushCbs[preFlushIndex])
-      ) {
+export function flushPreFlushCbs(seen?: CountMap, i = flushIndex) {
+  if (__DEV__) {
+    seen = seen || new Map()
+  }
+  for (; i < queue.length; i++) {
+    const cb = queue[i]
+    if (cb && cb.pre) {
+      if (__DEV__ && checkRecursiveUpdates(seen!, cb)) {
         continue
       }
-      activePreFlushCbs[preFlushIndex]()
+      queue.splice(i, 1)
+      i--
+      cb()
     }
-    activePreFlushCbs = null
-    preFlushIndex = 0
-    currentPreFlushParentJob = null
-    // recursively flush until it drains
-    flushPreFlushCbs(seen, parentJob)
   }
 }
 
 export function flushPostFlushCbs(seen?: CountMap) {
-  // flush any pre cbs queued during the flush (e.g. pre watchers)
-  flushPreFlushCbs()
   if (pendingPostFlushCbs.length) {
     const deduped = [...new Set(pendingPostFlushCbs)]
     pendingPostFlushCbs.length = 0
@@ -222,23 +189,30 @@ export function flushPostFlushCbs(seen?: CountMap) {
 const getId = (job: SchedulerJob): number =>
   job.id == null ? Infinity : job.id
 
+const comparator = (a: SchedulerJob, b: SchedulerJob): number => {
+  const diff = getId(a) - getId(b)
+  if (diff === 0) {
+    if (a.pre && !b.pre) return -1
+    if (b.pre && !a.pre) return 1
+  }
+  return diff
+}
+
 function flushJobs(seen?: CountMap) {
   isFlushPending = false
   isFlushing = true
   if (__DEV__) {
     seen = seen || new Map()
   }
 
-  flushPreFlushCbs(seen)
-
   // Sort queue before flush.
   // This ensures that:
   // 1. Components are updated from parent to child. (because parent is always
   //    created before the child so its render effect will have smaller
   //    priority number)
   // 2. If a component is unmounted during a parent component's update,
   //    its update can be skipped.
-  queue.sort((a, b) => getId(a) - getId(b))
+  queue.sort(comparator)
 
   // conditional usage of checkRecursiveUpdate must be determined out of
   // try ... catch block since Rollup by default de-optimizes treeshaking
@@ -270,11 +244,7 @@ function flushJobs(seen?: CountMap) {
     currentFlushPromise = null
     // some postFlushCb queued jobs!
     // keep flushing until it drains.
-    if (
-      queue.length ||
-      pendingPreFlushCbs.length ||
-      pendingPostFlushCbs.length
-    ) {
+    if (queue.length || pendingPostFlushCbs.length) {
       flushJobs(seen)
     }
   }