fix(ivy): maintain coalesced listeners order (#32484)

Prior to this commit, listeners order was not preserved in case we coalesce them to avoid triggering unnecessary change detection cycles. For performance reasons we were attaching listeners to existing events at head (always using first listener as an anchor), to avoid going through the list, thus breaking the order in which listeners are registered. In some scenarios this order might be important (for example with `ngModelChange` and `input` listeners), so this commit updates the logic to put new listeners at the end of the list. In order to avoid performance implications, we keep a pointer to the last listener in the list, so adding a new listener takes constant amount of time.

PR Close #32484
This commit is contained in:
Andrew Kushnir
2019-09-04 16:55:57 -07:00
committed by Matias Niemelä
parent a9ff48e67f
commit 098feec4a0
2 changed files with 40 additions and 3 deletions

View File

@ -238,5 +238,38 @@ describe('event listeners', () => {
expect(componentInstance.count).toEqual(1);
expect(componentInstance.someValue).toEqual(42);
});
it('should maintain the order in which listeners are registered', () => {
const log: string[] = [];
@Component({
selector: 'my-comp',
template: '<button dirA dirB (click)="count()">Click me!</button>',
})
class MyComp {
counter = 0;
count() { log.push('component.click'); }
}
@Directive({selector: '[dirA]'})
class DirA {
@HostListener('click')
count() { log.push('dirA.click'); }
}
@Directive({selector: '[dirB]'})
class DirB {
@HostListener('click')
count() { log.push('dirB.click'); }
}
TestBed.configureTestingModule({declarations: [MyComp, DirA, DirB]});
const fixture = TestBed.createComponent(MyComp);
fixture.detectChanges();
const button = fixture.nativeElement.firstChild;
button.click();
expect(log).toEqual(['dirA.click', 'dirB.click', 'component.click']);
});
});
});