Tests

[mhofman]

I didn't find any tests for the API so decided to write some: https://bl.ocks.org/mhofman/9824ef03535412caac194a57631a93b2

It seems that Chrome 74 doesn't implement everything right:

Please let me know if I forgot anything and feel free to use / modify however anyone wants.

[littledan]

It's great that you've written these tests! As you've seen, they have been very helpful in pushing the specification discussion forward. Would you be interested in updating them for the recent specification changes? Also, it could be helpful to develop these as a PR against test262 (not ready to land until the proposal reaches Stage 3). See https://github.com/tc39/test262/blob/master/CONTRIBUTING.md for information about how to get started. You can use test262-harness to run test262 against V8 with the experimental flag to verify your tests.

[mhofman]

Yeah I already started updating them.
They're actually part of a shim I'm working on, which I need as part of the sham I'm writing for my idea in #65
I'll be done with the shim soon, with support for node to start.

I'll look into re-writing it against test262.

[mhofman]

For test262, is there a cross platform way to request gc to be performed? The tests may be limited without it.

[gsathya]

For test262, is there a cross platform way to request gc to be performed?

Not yet.

cc @rwaldron @leobalter

[littledan]

I think it would make sense to add a hook for this. We'll have to be careful, as to trigger this, you need to trigger microtask checkpoints as well as gc to get these callbacks to reliably trigger. Would you be interested in opening a test262 issue to discuss this topic?

[mhofman]

I wrote myself the following helper for my tests :)
Not sure of the test262 environment, but hopefully something like that can work there too.

function taskTurn(): Promise<void> {
    return new Promise(resolve => setImmediate(resolve));
}

export function makeGcOf(
    gc: () => void,
    FinalizationGroup: FinalizationGroup.Constructor
) {
    return async function gcOf(target?: object): Promise<boolean> {
        let resolve: () => void;
        const collected = new Promise<void>(r => (resolve = r));
        const finalizationGroup = new FinalizationGroup<any>(resolve!);
        finalizationGroup.register(target || {}, 0);
        target = undefined;

        await taskTurn();
        gc();
        await collected;
        return true;
    };
}

Obviously gotta be careful at the call site to not hold the reference to the object.
Usually ends up being:

const collected = gcOf(object);
object = undefined!;
await collected;

But it can sometimes be a oneliner:

await gcOf(wearRef.deref());

I used setImmediate since I couldn't think of a way to wait for just the microtask queue to get emptied. At least with a new task, I'm sure we went through it :)

[littledan]

Sounds like a good start. The next step from here would be to look into integrating something like this into test262, with an issue there.

[leobalter]

Thanks for pinging me here. I have not started any work on this yet but seems like the correct first discussion. I intend to follow this up on regular work days.

…

On Sat, Apr 6, 2019 at 8:53 PM Daniel Ehrenberg ***@***.***> wrote: Sounds like a good start. The next step from here would be to look into integrating something like this into test262, with an issue there. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#70 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AASYkY1SwVF7jHOnrotUBO9gPvFaMgXuks5veUGlgaJpZM4cZdcI> .

[mhofman]

The initial version of my shim is ready, with updated tests: https://github.com/mhofman/tc39-weakrefs-shim/tree/master/src/tests

When running the tests in a browser with a global WeakRef and FinalizationGroup (i.e. Chrome with flags enabled), the shim uses those and the tests run against the browser implementation.

Next step is to rewrite the tests in test262.

[mhofman]

I've kept my tests mostly up to date with the spec, but I still haven't gotten around to port them to test262. I think the major blocker right now is a way to trigger collection. Most of the interesting tests require it.
@leobalter any suggestion on how to do that in test262?

[leobalter]

I'm currently using your tests as reference to meet coverage in the tests I've been doing for Test262. I believe the challenge is finding a way to communicate the api to a GC, if any is available. It's hard to create requirements in Test262 that are not specified in ECMA-262, but we can try some stuff there.

[mhofman]

Let me know if/how I can help.

Btw, I've been (slowly) updating the shim and tests in a branch. It's still WIP, but I've made a few updates to the tests that are not yet in master.