fix(scheduler): handle queueJob inside postFlushCbs

packages/scheduler/__tests__/scheduler.spec.ts

@@ -90,4 +90,27 @@ describe('scheduler', () => {
     await nextTick()
     expect(calls).toEqual(['job1', 'job2'])
   })
+
+  it('queueJob inside postFlushCb', async () => {
+    const calls: any = []
+    const job1 = () => {
+      calls.push('job1')
+    }
+    const cb1 = () => {
+      // queue another job in postFlushCb
+      calls.push('cb1')
+      queueJob(job2, cb2)
+    }
+    const job2 = () => {
+      calls.push('job2')
+    }
+    const cb2 = () => {
+      calls.push('cb2')
+    }
+
+    queueJob(job1, cb1)
+    queueJob(job2, cb2)
+    await nextTick()
+    expect(calls).toEqual(['job1', 'job2', 'cb1', 'cb2', 'job2', 'cb2'])
+  })
 })