fix: fix scheduler dupe invokes

packages/scheduler/__tests__/scheduler.spec.ts

@@ -22,8 +22,6 @@ describe('scheduler', () => {
       calls.push('job1')
       // job1 queues job2
       queueJob(job2)
-      // should be called sync
-      expect(calls).toEqual(['job1', 'job2'])
     }
     const job2 = () => {
       calls.push('job2')
@@ -60,8 +58,6 @@ describe('scheduler', () => {
       calls.push('job1')
       // job1 queues job2
       queueJob(job2, cb2)
-      // should be called sync
-      expect(calls).toEqual(['job1', 'job2'])
     }
     const job2 = () => {
       calls.push('job2')

packages/scheduler/src/index.ts

@@ -2,7 +2,7 @@ const queue: Array<() => void> = []
 const postFlushCbs: Array<() => void> = []
 const p = Promise.resolve()
 
-let flushing = false
+let hasPendingFlush = false
 
 export function nextTick(fn?: () => void): Promise<void> {
   return p.then(fn)
@@ -10,22 +10,18 @@ export function nextTick(fn?: () => void): Promise<void> {
 
 export function queueJob(job: () => void, postFlushCb?: () => void) {
   if (queue.indexOf(job) === -1) {
-    if (flushing) {
-      job()
-    } else {
-      queue.push(job)
+    queue.push(job)
+    if (!hasPendingFlush) {
+      hasPendingFlush = true
+      nextTick(flushJobs)
     }
   }
-  if (postFlushCb) {
+  if (postFlushCb && postFlushCbs.indexOf(postFlushCb) === -1) {
     postFlushCbs.push(postFlushCb)
   }
-  if (!flushing) {
-    nextTick(flushJobs)
-  }
 }
 
 function flushJobs() {
-  flushing = true
   let job
   while ((job = queue.shift())) {
     job()
@@ -33,5 +29,5 @@ function flushJobs() {
   while ((job = postFlushCbs.shift())) {
     job()
   }
-  flushing = false
+  hasPendingFlush = false
 }