Hi all,
I recently landed some test infrastructure for testing event targets for
memory leaks. This was part of fixing my service worker memory leak in bug
1447871. I wanted to let people know this existed and also ask for help
writing tests for more event targets.
To repeat, I need help writing more tests. Please see the list of untested
APIs at the bottom of this email.
To write an event target leak test you need to import this script:
<script type="text/javascript"
src="/tests/dom/events/test/event_leak_utils.js"></script>
And then call this function:
await checkForEventListenerLeaks("Worker", useWorker);
The string is just a name to make reporting assertions easier. The second
argument is a callback function where you exercise the API you want to test
for leaks. In this case I'm testing the worker API:
async function useWorker(contentWindow) {
contentWindow.messageCount = 0;
let w = new
contentWindow.Worker("data:application/javascript,self.postMessage({})");
w.onerror = _ => {
contentWindow.errorCount += 1;
};
await new Promise(resolve => {
w.onmessage = e => {
contentWindow.messageCount += 1;
resolve();
};
});
is(contentWindow.messageCount, 1, "message should be received");
}
The callback function should add an event listener that holds the given
contentWindow alive. Then try to leave the API in an active state to see
if its properly torn down when the test harness closes the window.
This particular test found that the Worker API leaks. See bug 1451381.
I've written tests for a number of APIs so far: ServiceWorker*, XHR,
Animation, MediaQueryList, EventSource, BroadcastChannel, MessageChannel,
SharedWorker, AbortSignal, WebSocket, Notification
The WebSocket and Notification tests have not landed yet because they
trigger assertions. These look like bugs in the respective APIs.
There are many, many event targets in the system, though. Using searchfox
to look for subclasses of DOMEventTargetHelper I came up with a list of
event targets that are not currently tested. Some of these are deprecated
or not exposed. But a lot of these are web exposed. It would be really
great to get this kind of simple leak test written for these APIs.
ContentFrameMessageManager
DOMRequest
ScreenOrientation
BatteryManager
OffscreenCanvas
ConstructibleEventTarget
FetchObserver
FileReader
IDBFileHandle
IDBMutableFileHandle
IDWrapperCache (and sub classes)
DOMMediaStream
MediaDevices
MediaRecorder
MediaStreamTrack
MediaTrack
MediaTrackList
TextTrack
TextTrackCue
TextTrackList
MediaKeySession
ImageCapture
MediaSource
SourceBuffer
SourceBufferList
AudioContext
AudioNode
SpeechRecognition
SpeechSynthesis
SpeechSynthesisUtterance
MIDIAccess
MIDIPort
Connection
TCPServerSocket
TCPSocket
UDPSocket
PaymentRequest
Performance
PermissionStatus
PresentationAvailability
PresentationConnection
PresentationConnectList
PresentationRequest
VRDisplay
FontFaceSet
ChannelWrapper
StreamFilter
If one of these targets falls in your area, please try to find the time to
write a small test as described above. Also, please link it against the
meta bug here:
https://bugzilla.mozilla.org/show_bug.cgi?id=1451787
Thanks!
Ben
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