RxJS观察:为什么回调会触发两次?

从一个角度为6的组件考虑这个代码:

class AppComponent  {
  subject = new Subject<any>();
  one = this.subject.pipe(share(), tap(e => log('one emits')));
  two = this.one.pipe(tap(e => log('two emits')));
  three = this.one.pipe(delay(500), tap(e => log('three emits')));

  ngOnInit() {
    this.two.subscribe(e => log('two received'));
    this.three.subscribe(e => log('three received'));    
    this.subject.next();
  }  
}

ngOnInit 执行,这是记录的内容:

一发

收到两个

一发

收到三个

one share 管道制造商中的操作员 two 和 three

Source on Stackblitz