LibWeb: Shadow Realm integration - part 2

[shannonbooth]

Second stage of shadow realm integration into LibWeb sitting ontop of #1927

The step after this is to change HTML::Script to operate on realm's instead of environment setting objects. After that, we should then be able to hook up the VM hook to actually initialize the shadow realm global object - which is enough for the test case of:

<script>
async function test() {
    const realm = new ShadowRealm()
    const aSync = realm.evaluate(`async () => 1 + 1`)
    aSync()
}

test();
</script>

To not crash :^)

Edit: For a mostly-working implementation, see: #1993

[ADKaster]

Pre-review comment: I remember Luke Warlow mentioning in discord that the example there is supposed to throw, do we handle that yet? or is that later :)

[shannonbooth]

Pre-review comment: I remember Luke Warlow mentioning in discord that the example there is supposed to throw, do we handle that yet? or is that later :)

I have that specific test case working (throwing an exception as expected) - but it needs another set of changes ontop of this.

Primarily:

• Changing HTML::Script to hold a Realm instead of Settings Object
• Implementing the concept of a 'synthetic realm' which is stored in [[HostDefined]] for a shadow realm (a primary realm is effectively meant to represent the same thing as what LibWeb uses today)
• Hooking up the host defined callback from LibJS to LibWeb in MainVMThread.cpp
• Defining the shadow realm global object

Which is enough for that test case to work, but we crash when running the WPT tests for Shadow Realms are there are still some items to check off to implement after that

[shannonbooth]

Pushed rebase to fix de conflict

[ADKaster]

This part seems pretty reasonable to me. Two comments about how we're going to follow-up or track changes to other specs, but they don't need to be addressed before getting this set in main, I don't think.

I think after this shadow realm work is in, we can revisit the libgc changes. We'll want that for wasm gc at the very least. And would be best to not be juggling too many sweeping changes at once.

[ADKaster]

In the first commit you updated the copied spec text language to add "principal" for the ESO. Seems a miss here, and in Animations/Animation.cpp.

... and more. Perhaps best to leave that to a tracking issue in html/shadow realms

[shannonbooth]

Whoops, that is a miss on my end for this one. It is covered in the open merge request, see: https://whatpr.org/html/9893/b8ea975...32ad7a4/media.html#dom-audio

I did a scan over the spec folders for specs which have an open MR, but missed this one since it's in the Bindings folder. Will do a second scan over and adjust