JiaLiPassion 4a8d5ae970 fix(core): markDirty() should only mark flags when really scheduling tick. (#39316)
Close #39296

Fix an issue that `markDirty()` will not trigger change detection.

The case is for example we have the following component.

```
export class AppComponent implements OnInit {
  constructor(private router: Router) {}

  ngOnInit() {
    this.router.events
      .pipe(filter((e) => e instanceof NavigationEnd))
      .subscribe(() => ɵmarkDirty(this));
  }
}

export class CounterComponent implements OnInit, OnDestroy {
  ngOnInit() {
    this.countSubject.pipe(takeUntil(this.destroy)).subscribe((count) => {
      this.count = count;
      ɵmarkDirty(this);
    });
  }
```

Then the app navigate from `AppComponent` to `CounterComponent`,
so there are 2 `markDirty()` call at in a row.

The `1st` call is from `AppComponent` when router changed, the
`2nd` call is from `CounterComponent.ngOnInit()`.

And the `markDirty()->scheduleTick()` code look like this

```
function scheduleTick(rootContext, flags) {
    const nothingScheduled = rootContext.flags === 0 /* Empty */;
    rootContext.flags |= flags;
    if (nothingScheduled && rootContext.clean == _CLEAN_PROMISE) {
      rootContext.schedule(() => {
	...
        if (rootContext.flags & RootContextFlags.DetectChanges)
          rootContext.flags &= ~RootContextFlags.DetectChanges;
          tickContext();

        rootContext.clean = _CLEAN_PROMISE;
        ...
      });
```

So in this case, the `1st` markDirty() will
1. set rootContext.flags = 1
2. before `tickContext()`, reset rootContext.flags = 0
3. inside `tickContext()`, it will call `CounterComponent.ngOnint()`,
   so the `2nd` markDirty() is called.
4. and the `2nd` scheduleTick is called, `nothingScheduled` is true,
   but rootContext.clean is not `_CLEAN_PROMISE` yet, since the `1st` markDirty tick
   is still running.
5. So nowhere will reset the `rootContext.flags`.
6. then in the future, any other `markDirty()` call will not trigger the tick, since
   `nothingScheduled` is always false.

So `nothingScheduled` means no tick is scheduled, `rootContext.clean === _CLEAN_PROMISE`
means no tick is running.
So we should set the flags to `rootContext` only when `no tick is scheudled or running`.

PR Close #39316
2020-10-29 16:07:10 -07:00
2020-10-20 13:22:37 -07:00
2020-01-27 09:31:22 -08:00
2020-01-13 07:21:43 -08:00
2020-10-15 14:08:17 -07:00
2020-10-21 11:59:40 -07:00

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