[scoped-registries] Describe interaction with declarative shadow DOM

[justinfagnani]

Fixes #914

This adds a shadowrootregistry attribute for <template shadowrootmode> and ShadowRoot.prototype.scopedRegistry, as discussed in the String 2023 F2F meeting.

[justinfagnani]

@rniwa @mfreed7 I updated this PR with what we resolved from last weeks meeting, by adding ShadowRoot.prototype.scopedRegistry.

Can one of you review? Thanks!

[rniwa]

We should probably have "shadowRoot.customElements" instead of "shadowRoot.scopedRegistry" to be consistent with the global registry.

[justinfagnani]

I think that would be shadowRoot.customElements instead of shadwoRoot.registry?

[rniwa]

right.

[mfreed7]

Hmm, I find shadowRoot.customElements a bit harder to understand, as it's defined. In other words, this boolean is true "when the shadowRoot has a scoped registry, or is waiting for a scoped registry". I feel like "registry" should be at least somewhere in the name of the property, right?

[justinfagnani]

@rniwa meant that registry should be named customElements to match the global window.customElements.

shadowRoot.scopedRegistry would still be the boolean, if that's agreeable. (I don't think we do is or has prefixes in the DOM, correct?)

[mfreed7]

Oh! Thanks, I missed that. I agree with renaming shadowRoot.registry to shadowRoot.customElements, which is exactly what you both wrote, but I failed to read correctly.

The DOM does use is sometimes, e.g. isConnected, isTrusted, isMap, isContentEditable, etc. The has prefix (which seems like what we'd want here) is also used, though less so. For example, hasBeenActive. If has is acceptable, I'd definitely lobby for renaming shadowRoot.scopedRegistry to shadowRoot.hasScopedRegistry.

[justinfagnani]

I'll change to hasScopedRegistry in this PR and we can see what other reviewers think.

As for registry vs customElements: that effects the argument to attachShadow() too. I think I should make a separate PR for both so the change is more obvious?

[EisenbergEffect]

What is the status of this WRT the latest scope registry implementations in Chromium and WebKit? Is shadowrootregistry="" on <template> supported as part of that work? And do we have a way to associate the scoped registry later on, such as through a registry or customElements property somewhere?

I'm playing around with things now, and since server rendering with DSD is an important strategy for me, I'm trying to understand how best to integrate that with scoped registries, given the recent progress in browser engines.

[rniwa]

What is the status of this WRT the latest scope registry implementations in Chromium and WebKit? Is shadowrootregistry="" on <template> supported as part of that work? And do we have a way to associate the scoped registry later on, such as through a registry or customElements property somewhere?

I'm playing around with things now, and since server rendering with DSD is an important strategy for me, I'm trying to understand how best to integrate that with scoped registries, given the recent progress in browser engines.

There is no support yet. We need to solidify the proposal to figure out what exactly we're gonna do here.