data URL dedicated workers and agent clusters

[annevk]

For whatwg/html#5476.

[domenic]

Interesting, so browsers don't even do this for iframes...

[domenic]

Should we test WebAssembly.Memory too?

[annevk]

That follows the underlying object (a literal AB or SAB) so I don't think it's needed, but we could. If you also wanted to test it backed by AB though we'd have to invert all the pass conditions for that variant.

[domenic]

I think this can never happen since both message and messageerror will cause a "FAIL" to be posted? More reason to change the messages posted in the way I describe above.

[guest271314]

FYI this appears to be "working as intended" at Firefox 77.

[annevk]

Thanks @domenic, hopefully this is a bit better.

[guest271314]

One item this test reveals is that security.block_script_with_wrong_mime and security.block_Worker_with_wrong_mime are not stopping the data URL with no MIME type from loading. Am not sure if that is working as intended.

[annevk]

@guest271314 that sounds like a bug. Can you create a separate test for that? I'll add text/javascript here.

[domenic]

LGTM. Glad to see that frames are in a separate agent cluster after all.

[guest271314]

@annevk

that sounds like a bug. Can you create a separate test for that?

Not sure if that is currently testable and verifiable at WPT, see #20284 (comment).

Opened console at Nightly and ran

#20284 (comment)

dataURLWorker = `
  onmessage = () => self.postMessage("FAIL");
  onmessageerror = () => self.postMessage("PASS");
`;
[
  new ArrayBuffer()
].forEach(instance => {

    const worker = new Worker(`data:,${dataURLWorker}`);
    worker.onmessage = e => console.log(e.data);
    worker.postMessage(instance);
});

Workers are not prohibited from loading any particular MIME type, correct? What is the expected result of a data URL without MIME type being set as URL to a Worker?

Should a Firefox bug be filed?

[annevk]

@guest271314 I'd make a test for module workers to ensure it's enforced there. Perhaps also with a blob URL and such. If user agents eventually also enforce things for classic workers we could extend those tests.