finalization-registry-microtasks.html

<!DOCTYPE html>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<script type="module">

// Keep FinalizationRegistry global to avoid it being reclaimed by garbage
// collections that may happen until the registry is processed in microtasks.
let fr1;
let fr2;

async_test(t => {
  let last_task_that_ran = "";
  let num_microtasks_that_ran = 0;

  const callback = () => {
    last_task_that_ran = 'finalizer';
    Promise.resolve().then(t.step_func(function() {
      assert_equals(last_task_that_ran, 'finalizer');
      last_task_that_ran = 'microtask';
      // The two FinalizationRegistries below run their finalizers in two
      // separate tasks. Those tasks should be each followed by a microtask
      // checkpoint, thus the counter here.
      if (++num_microtasks_that_ran == 2) t.done();
    }));
  };

  fr1 = new FinalizationRegistry(callback);
  fr2 = new FinalizationRegistry(callback);

  (function() {
    let garbage = {};
    fr1.register(garbage, 'holdings1');
    fr2.register(garbage, 'holdings2');
    garbage = null;
  })();

  gc();
}, 'FinalizationRegistry finalizers have a microtask checkpoint on completion');
</script>
chromium/third_party/blink/web_tests/js/weakrefs/finalization-registry-microtasks.html
