@angular/core

What are @angular/core's main functionalities?

"@Component({ selector: 'app-root', templateUrl: './app.component.html', styleUrls: ['./app.component.css'] }) export class AppComponent { title = 'My Angular App'; }"

"constructor(private myService: MyService) {}"

"@Directive({ selector: '[appHighlight]' }) export class HighlightDirective { constructor(el: ElementRef) { el.nativeElement.style.backgroundColor = 'yellow'; } }"

18.0.0-next.0 (2024-03-14)

Breaking Changes

core

• OnPush views at the root of the application need to be marked dirty for their host bindings to refresh. Previously, the host bindings were refreshed for all root views without respecting the OnPush change detection strategy.
• The ComponentFixture autoDetect feature will no longer refresh the component's host view when the component is OnPush and not marked dirty. This exposes existing issues in components which claim to be OnPush but do not correctly call markForCheck when they need to be refreshed. If this change causes test failures, the easiest fix is to change the component to ChangeDetectionStrategy.Default.
• When Angular runs change detection, it will continue to refresh any views attached to ApplicationRef that are still marked for check after one round completes. In rare cases, this can result in infinite loops when certain patterns continue to mark views for check using ChangeDetectorRef.detectChanges. This will be surfaced as a runtime error with the NG0103 code.
• The ComponentFixture.autoDetect feature now executes change detection for the fixture within ApplicationRef.tick. This more closely matches the behavior of how a component would refresh in production. The order of component refresh in tests may be slightly affected as a result, especially when dealing with additional components attached to the application, such as dialogs. Tests sensitive to this type of change (such as screenshot tests) may need to be updated. Concretely, this change means that the component will refresh before additional views attached to ApplicationRef (i.e. dialog components). Prior to this change, the fixture component would refresh after other views attached to the application.
• The exact timing of change detection execution when using event or run coalescing with NgZone is now the first of either setTimeout or requestAnimationFrame. Code which relies on this timing (usually by accident) will need to be adjusted. If a callback needs to execute after change detection, we recommend afterNextRender instead of something like setTimeout.
• Newly created and views marked for check and reattached during change detection are now guaranteed to be refreshed in that same change detection cycle. Previously, if they were attached at a location in the view tree that was already checked, they would either throw ExpressionChangedAfterItHasBeenCheckedError or not be refreshed until some future round of change detection. In rare circumstances, this correction can cause issues. We identified one instance that relied on the previous behavior by reading a value on initialization which was queued to be updated in a microtask instead of being available in the current change detection round. The component only read this value during initialization and did not read it again after the microtask updated it.

router

• Guards can now return RedirectCommand for redirects in addition to UrlTree. Code which expects only boolean or UrlTree values in Route types will need to be adjusted.

compiler-cli

| Commit | Type | Description | | -- | -- | -- | | 9b424d7224 | fix | preserve original reference to non-deferrable dependency (#54759) |

core

| Commit | Type | Description | | -- | -- | -- | | 64f870c12b | fix | ApplicationRef.tick should respect OnPush for host bindings (#53718) (#53718) | | 8cad4e8cbe | fix | ComponentFixture autoDetect respects OnPush flag of host view (#54824) | | ba8e465974 | fix | Change Detection will continue to refresh views while marked for check (#54734) | | 24bc0ed4f2 | fix | ComponentFixture autodetect should detect changes within ApplicationRef.tick (#54733) | | 10c5cdb49c | fix | ensure change detection runs in a reasonable timeframe with zone coalescing (#54578) | | ad045efd4b | fix | Ensure views marked for check are refreshed during change detection (#54735) | | 700c0520bb | fix | Update ApplicationRef.tick loop to only throw in dev mode (#54848) |

router

| Commit | Type | Description | | -- | -- | -- | | 8735af08b9 | feat | Add ability to return UrlTree with NavigationBehaviorOptions from guards (#45023) |

<a name="17.3.0"></a>