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// META: script=/common/gc.js
// META: script=resources/maybe-garbage-collect.js
// ├──> maybeGarbageCollectAndCleanupAsync
// ├──> maybeGarbageCollectAsync
// └──> resolveGarbageCollection
/*---
esid: sec-finalization-registry-target
info: |
FinalizationRegistry ( cleanupCallback )
FinalizationRegistry.prototype.cleanupSome ( [ callback ] )
...
4. If callback is not undefined and IsCallable(callback) is false, throw a TypeError exception.
5. Perform ? CleanupFinalizationRegistry(finalizationRegistry, callback).
6. Return undefined.
Execution
At any time, if an object obj is not live, an ECMAScript implementation may perform the following steps atomically:
1. For each WeakRef ref such that ref.[[Target]] is obj,
a. Set ref.[[Target]] to empty.
2. For each FinalizationRegistry finalizationRegistry such that finalizationRegistry.[[Cells]] contains cell, such that cell.[[Target]] is obj,
a. Set cell.[[Target]] to empty.
b. Optionally, perform ! HostCleanupFinalizationRegistry(finalizationRegistry).
---*/
let cleanupCallback = 0;
let holdings = [];
function cb(holding) {
holdings.push(holding);
}
let finalizationRegistry = new FinalizationRegistry(function() {
cleanupCallback += 1;
});
function emptyCells() {
let target = {};
finalizationRegistry.register(target, 'a');
let prom = maybeGarbageCollectAndCleanupAsync(target);
target = null;
return prom;
}
function queueMicrotaskByMutationObserver(callback) {
const textNode = document.createTextNode('');
new MutationObserver(callback).observe(textNode, { characterData: true });
textNode.data = 1;
}
promise_test(() => {
return (async () => {
assert_implements(
typeof FinalizationRegistry.prototype.cleanupSome === 'function',
'FinalizationRegistry.prototype.cleanupSome is not implemented.'
);
assert_implements(
typeof MutationObserver === 'function',
'MutationObserver is not implemented.'
);
let ticks = 0;
await emptyCells();
await queueMicrotaskByMutationObserver(() => ticks++);
finalizationRegistry.cleanupSome(cb);
// cleanupSome will be invoked if there are empty cells left. If the
// cleanupCallback already ran, then cb won't be called.
let expectedCalled = cleanupCallback === 1 ? 0 : 1;
// This asserts the registered object was emptied in the previous GC.
assert_equals(holdings.length, expectedCalled, 'cleanupSome callback for the first time');
// At this point, we can't assert if cleanupCallback was called, because it's
// optional. Although, we can finally assert it's not gonna be called anymore
// for the other executions of the Garbage Collector.
// The chance of having it called only happens right after the
// cell.[[Target]] is set to empty.
assert_true(cleanupCallback >= 0, 'cleanupCallback might be 0');
assert_true(cleanupCallback <= 1, 'cleanupCallback might be 1');
// Restoring the cleanupCallback variable to 0 will help us asserting the
// finalizationRegistry callback is not called again.
cleanupCallback = 0;
await maybeGarbageCollectAsync();
await queueMicrotaskByMutationObserver(() => ticks++);
finalizationRegistry.cleanupSome(cb);
assert_equals(holdings.length, expectedCalled, 'cleanupSome callback is not called anymore, no empty cells');
assert_equals(cleanupCallback, 0, 'cleanupCallback is not called again #1');
await maybeGarbageCollectAsync();
await queueMicrotaskByMutationObserver(() => ticks++);
finalizationRegistry.cleanupSome(cb);
assert_equals(holdings.length, expectedCalled, 'cleanupSome callback is not called again #2');
assert_equals(cleanupCallback, 0, 'cleanupCallback is not called again #2');
assert_equals(ticks, 3, 'ticks is 3');
if (holdings.length) {
assert_array_equals(holdings, ['a']);
}
await maybeGarbageCollectAsync();
})().catch(resolveGarbageCollection);
}, 'cleanupCallback has only one optional chance to be called for a GC that cleans up a registered target.');
|
