feat(scheduler): supports nextick execution on queuejob first.

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

@@ -644,4 +644,27 @@ describe('scheduler', () => {
     await nextTick()
     expect(calls).toEqual(['cb2', 'cb1'])
   })
+
+  test('nextick callback should be executed after the queuejob', async () => {
+    let val = 1
+    queueJob(() => {
+      val = 3
+    })
+    await nextTick(() => {
+      val = 2
+    })
+    expect(val).toBe(2)
+
+    const p = new Promise<void>(r => {
+      nextTick(() => {
+        val = 2
+        r()
+      })
+      queueJob(() => {
+        val = 3
+      })
+    })
+    await p
+    expect(val).toBe(2)
+  })
 })

packages/runtime-core/src/scheduler.ts

@@ -61,7 +61,17 @@ export function nextTick<T = void, R = void>(
   fn?: (this: T) => R,
 ): Promise<Awaited<R>> {
   const p = currentFlushPromise || resolvedPromise
-  return fn ? p.then(this ? fn.bind(this) : fn) : p
+  let wrapperFn: ((this: T) => R | Promise<R> | undefined) | undefined = fn
+  if (!currentFlushPromise) {
+    wrapperFn = function () {
+      if (!fn) return
+      if (currentFlushPromise) {
+        return currentFlushPromise.then(fn.bind(this))
+      }
+      return fn.call(this)
+    }
+  }
+  return wrapperFn ? p.then(this ? wrapperFn.bind(this) : wrapperFn) : p
 }
 
 // Use binary-search to find a suitable position in the queue. The queue needs