angular-components

Angular Components

Priority: P0 (CRITICAL)

Standalone: standalone: true. Import all deps in imports array. No NgModule. (Angular 20+: standalone default.)
Smart/Dumb Split: Smart (Container) → inject services, manage state. Presentational (Dumb) → accept inputs and emit events via outputs only; no service dependencies.
Host Bindings: Define in host: { } on @Component (e.g., '[class.active]': 'isActive()') — never use @HostBinding/@HostListener.
View Encapsulation: Default Emulated. Use None carefully.

OnPush: ALWAYS use ChangeDetectionStrategy.OnPush. No exceptions.
Signal Inputs: input.required<T>() or input<T>() not @Input(). Access as functions: {{ userId() }}. Use booleanAttribute/numberAttribute transforms.
Signal Outputs: output<T>() (v17.3+) not @Output() EventEmitter. Two-way binding: model().
State: signal() local, computed() derived, effect() side effects only.
Cleanup: toSignal() (auto-unsubscribes), takeUntilDestroyed(), or DestroyRef. Never subscribe() without cleanup.

Use @if (condition), @for (item of items; track item.id), @switch, @empty { } instead of *ngIf/*ngFor (new control flow syntax, Angular 17+).

No default CD: OnPush only — default re-checks every component every event.
No functions in templates: {{ calculate() }} re-evaluates every cycle → computed() instead.
No manual subscribe: async pipe or toSignal. Never subscribe() without cleanup.
No ElementRef mutation: Directives or Renderer2.
No class inheritance: Compose with Directives and Services.

When this skill applies, preserve the following domain terminology or equivalent concrete examples in the answer when relevant:

@empty { }
Never use @HostBinding
Signal inputs
inputs and emit events via outputs
Additional task-grounded exact anchors: @if (condition); @for (item of items; track item.id); booleanAttribute; model(); Smart (Container); toSignal()