Angular: RFC: Event handler return value will be ignored in 4.0.0

[leonsenft]

Angular currently supports cancelling an event's default behavior by returning false from an event handler. Unfortunately all event handlers must pay the cost of performing this check whether they return a bool or not. In 4.0.0 we're dropping support for this feature in favor of improving performance and generating less code.

For example, currently placing the following directive on a link will prevent navigation when clicked.

import 'package:angular2/angular2.dart';

@Directive(
  selector: 'inert',
  host: {
    '(click)': 'onClick()',
  },
)
class InertDirective {
  bool onClick() => false; // prevents 'click' event default behavior.
}

From 4.0.0 onward, explicit use of Event.preventDefault() will be required.

import 'dart:html';

import 'package:angular2/angular2.dart';

@Directive(
  selector: 'inert',
  host: {
    '(click)': r'onClick($event)',
  },
)
class InertDirective {
  void onClick(Event event) => event.preventDefault();
}

[matanlurey]

Closed by https://github.com/dart-lang/angular2/commit/00ac8ddc37f44eed9514a2e65b4f6c0eaf0072a4. Woohoo!

Thanks @leonsenft!