tests/lib_2/html/native_gc_test.dart

// @dart = 2.9
library NativeGCTest;

import 'dart:async';
import 'dart:html';

import 'package:expect/minitest.dart';

var testEvent = new EventStreamProvider<Event>('test');

void testEventListener() {
  final int N = 1000000;
  final int M = 1000;

  var div;
  for (int i = 0; i < M; ++i) {
    // This memory should be freed when the listener below is
    // collected.
    List l = new List(N);

    // Record the iteration number.
    l[N - 1] = i;

    div = new Element.tag('div');
    testEvent.forTarget(div).listen((_) {
      // Only the final iteration's listener should be invoked.
      // Note: the reference to l keeps the entire list alive.
      expect(l[N - 1], M - 1);
    });
  }

  final event = new Event('test');
  div.dispatchEvent(event);
}

Future<Null> testWindowEventListener() {
  String message = 'WindowEventListenerTestPingMessage';

  Element testDiv = new DivElement();
  testDiv.id = '#TestDiv';
  document.body.append(testDiv);
  window.onMessage.listen((e) {
    if (e.data == message) testDiv.click();
  });

  for (int i = 0; i < 100; ++i) {
    triggerMajorGC();
  }

  final done = new Completer<Null>();
  testDiv.onClick.listen(((_) {
    done.complete();
  }));
  window.postMessage(message, '*');
  return done.future;
}

main() async {
  testEventListener();
  await testWindowEventListener();
}

void triggerMajorGC() {
  List list = new List(1000000);
  Element div = new DivElement();
  div.onClick.listen((e) => print(list[0]));
}