TIL you can put @input() decorator on setter and transform the value. It does not have to be put on property.

user_role_component.dart

@Component( selector: 'user-role',
            template: r'''
<span *ngIf="userRole != null && long" >{{ userRole.completeLabel }}</span>
<span *ngIf="userRole != null && !long" >{{ userRole.label}}</span>
''')
class UserRoleComponent {

  UserRole userRole;

  @Input()
  bool long = false;

  @Input()
  set role(var role) {
    if (role is UserRole) this.userRole = role as UserRole;
    final UserRole found = findRoleDescriptor(role);
    this.userRole = found;
  }
}

no 4th line there is space missing :-D