Add Scoped Custom Element Registries by annevk · Pull Request #10869 · whatwg/html

annevk · 2024-12-17T17:33:19Z

Please do not comment directly on this PR unless asked. It's a big change and we want to keep it manageable. Use #10854 instead.

DOM PR: whatwg/dom#1341.

Tests: web-platform-tests/wpt#50790

At least two implementers are interested (and none opposed):
- WebKit
- Gecko
- Chromium
Tests are written and can be reviewed and commented upon at:
- custom-elements: merge revamped-scoped-registry and custom-element-registry into registries web-platform-tests/wpt#51953
Implementation bugs are filed:
- Chromium: https://issues.chromium.org/issues/399124619
- Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1874414
- WebKit: N/A
Corresponding HTML AAM & ARIA in HTML issues & PRs: N/A
MDN issue is filed: Scoped Custom Element Registries mdn/content#38266
The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

/custom-elements.html ( diff )
/document-lifecycle.html ( diff )
/document-sequences.html ( diff )
/dom.html ( diff )
/indices.html ( diff )
/infrastructure.html ( diff )
/parsing.html ( diff )
/scripting.html ( diff )

HTML PR: whatwg/html#10869. Tests: ... Closes #1339.

source

HTML PR: whatwg/html#10869. Tests: ... Closes #1339.

foolip

Editorial review pass up to the CustomElementRegistry IDL block.

foolip · 2025-03-19T15:34:25Z

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     <li><dfn data-x="concept-document-type" data-x-href="https://dom.spec.whatwg.org/#concept-document-type">document type</dfn> concept</li>
     <li><dfn data-x="concept-DocumentFragment-host" data-x-href="https://dom.spec.whatwg.org/#concept-documentfragment-host">host</dfn> concept</li>
-     <li>The <dfn data-x-href="https://dom.spec.whatwg.org/#concept-shadow-root">shadow root</dfn> concept, and its <dfn data-x-href="https://dom.spec.whatwg.org/#shadowroot-delegates-focus">delegates focus</dfn>, <dfn data-x-href="https://dom.spec.whatwg.org/#shadowroot-available-to-element-internals">available to element internals</dfn>, <dfn data-x-href="https://dom.spec.whatwg.org/#shadowroot-clonable">clonable</dfn>, and <dfn data-x="shadow-serializable" data-x-href="https://dom.spec.whatwg.org/#shadowroot-serializable">serializable</dfn>.</li>
+     <li>The <dfn data-x-href="https://dom.spec.whatwg.org/#concept-shadow-root">shadow root</dfn> concept, and its <dfn data-x-href="https://dom.spec.whatwg.org/#shadowroot-delegates-focus">delegates focus</dfn>, <dfn data-x-href="https://dom.spec.whatwg.org/#shadowroot-available-to-element-internals">available to element internals</dfn>, <dfn data-x-href="https://dom.spec.whatwg.org/#shadowroot-clonable">clonable</dfn>, <dfn data-x="shadow-serializable" data-x-href="https://dom.spec.whatwg.org/#shadowroot-serializable">serializable</dfn>, <dfn data-x="shadow-root-custom-element-registry" data-x-href="https://whatpr.org/dom/1341.html#shadowroot-custom-element-registry">custom element registry</dfn>, and <dfn data-x-href="https://whatpr.org/dom/1341.html#shadowroot-keep-custom-element-registry-null">keep custom element registry null</dfn>.</li>


Comment to ensure that the URLs here change before this is merged.

foolip · 2025-03-19T15:35:14Z

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-                       <dfn data-x="concept-node-clone-parent" data-x-href="https://dom.spec.whatwg.org/#clone-a-node-parent"><var>parent</var></dfn>, and the concept of
+                       <dfn data-x="concept-node-clone-subtree" data-x-href="https://dom.spec.whatwg.org/#clone-a-node-subtree"><var>subtree</var></dfn>,
+                       <dfn data-x="concept-node-clone-parent" data-x-href="https://dom.spec.whatwg.org/#clone-a-node-parent"><var>parent</var></dfn>, and
+                       <dfn data-x="concept-node-clone-fallbackRegistry" data-x-href="https://dom.spec.whatwg.org/#clone-a-node-fallbackregistry"><var>fallbackRegistry</var></dfn>, and the concept of


Need to double check that this URL is correct before landing.

source

foolip · 2025-03-19T15:56:37Z

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  attribute is a <span>boolean attribute</span>.</p>

+  <p>The <dfn element-attr for="template"><code
+  data-x="attr-template-shadowrootcustomelementregistry">shadowrootcustomelementregistry</code></dfn>


It looks like this the longest attribute name so far, 31 characters. Maybe that's right, but have you thought about shorter names that you also think are OK?

It's not ideal, but anything else would end up being inconsistent with the rest of the APIs.

I guess it will be a fun piece of trivia to know if nothing else :)

source

foolip · 2025-03-19T16:04:01Z

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+  <p>To <dfn export>look up a custom element definition</dfn>, given null or a
+  <code>CustomElementRegistry</code> object <var>registry</var>, string-or-null


This style seems more common for nullable objects:

Suggested change

<p>To <dfn export>look up a custom element definition</dfn>, given null or a

<code>CustomElementRegistry</code> object <var>registry</var>, string-or-null

<p>To <dfn export>look up a custom element definition</dfn>, given a

<code>CustomElementRegistry</code>-or-null <var>registry</var>, string-or-null

(I found NavigationFocusReset-or-null as the example follow.)

foolip

Editorial review done.

foolip · 2025-03-19T19:20:07Z

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-  DOMString? <span data-x="dom-CustomElementRegistry-getName">getName</span>(CustomElementConstructor constructor);
-  <span data-x="idl-Promise">Promise</span>&lt;<span>CustomElementConstructor</span>&gt; <span data-x="dom-CustomElementRegistry-whenDefined">whenDefined</span>(DOMString name);
-  [<span>CEReactions</span>] undefined <span data-x="dom-CustomElementRegistry-upgrade">upgrade</span>(<span>Node</span> root);
+  <span data-x="dom-CustomElementRegistry">constructor</span>();


For other reviewers: It's hard to tell from the diff, so the new things here are the constructor and the initialize() method.

source

foolip · 2025-03-19T19:39:59Z

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+      <p><span data-x="map remove">Remove</span> <var>registry</var>'s <span>relevant global
+      object</span>'s <span>active custom element constructor map</span>[<var>C</var>].</p>
+
+      <p class="note">This is a no-op if <var>C</var> immediately calls <code


Is the case where super() isn't called covered by the tests?

web-platform-tests/wpt#51889

foolip · 2025-03-19T19:44:29Z

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+       <li><p>If <var>current node</var>'s <span data-x="element-custom-element-registry">custom
+       element registry</span> is not <var>shadow</var>'s <span
+       data-x="shadow-root-custom-element-registry">custom element registry</span>, then append
+       "<code data-x=""> shadowrootcustomelementregistry=&quot;&quot;</code>".</p></li>


How does this fit together with the extension point, the reason that the IDL attribute reflects as a string and not a boolean? Shouldn't this preserve the attribute value for consistency / to avoid a change in behavior later?

It seems okay for serialization to change at that point.

foolip · 2025-03-19T19:48:17Z

OK, so the main thing I'm left wondering point is the reasoning behind shadowrootcustomelementregistry being a boolean attribute, but the shadowRootCustomElementRegistry IDL attribute reflecting as a string, per the comment in the spec.

If the value is the empty string, shadowRootCustomElementRegistry will be the empty string (falsy), but if it was reflected as a boolean it would be true. If the attribute isn't present, shadowRootCustomElementRegistry would also be the empty string, so how does one distinguish between the typical "attribute is present" and "attribute is absent" cases?

Maybe it makes sense if I learn more about how this might be extended in the future.

source

HTML PR: whatwg/html#10869. Tests: ... Closes #1339.

DOM PR: whatwg/dom#1341. Tests: ... Closes #10854.

annevk · 2025-04-07T15:33:36Z

About shadowRootCustomElementRegistry: this is indeed kinda useless now, but the IDL attributes on template are not that useful to begin with. Making it reflect as a string will indeed allow for named scoped registries in the future. That you have to use hasAttribute() for now is not that big of a deal I think. I prefer that over making it reflect as a nullable string, even though that would be possible now that we made a tweak to reflection for ARIA.

foolip · 2025-04-10T15:37:28Z

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   </li>
  </ol>

+  <p class="note">Once the custom element registry of a node is initialized to a


Thanks for adding this note!

foolip · 2025-04-10T15:38:39Z

I've finished editorial review of this and whatwg/dom#1341 now, but I'd like @mfreed7 to weigh in to confirm implementer interest on behalf of Chromium.

mfreed7 · 2025-04-10T16:13:11Z

I've finished editorial review of this and whatwg/dom#1341 now, but I'd like @mfreed7 to weigh in to confirm implementer interest on behalf of Chromium.

Thanks for the review! You can mark Chromium as interested.

…gistry into registries And rename away from .tentative for the Revamped Scoped Custom Element Registry tests as whatwg/html#10869 and whatwg/dom#1341 are about to land.

HTML PR: whatwg/html#10869. Tests: web-platform-tests/wpt#50790, web-platform-tests/wpt#50860, and web-platform-tests/wpt#51953. Closes #1339.

This implements the IDL definitions per the spec issue[1], however all methods are basic stubs and do not execute any logic - the logic will come with later patches. I2P: https://groups.google.com/a/chromium.org/g/blink-dev/c/um-9YjJWyEQ/m/MhKN0L7FAgAJ Spec PRs: HTML: whatwg/html#10869 DOM: whatwg/dom#1341 [1]: whatwg/html#10854 Bug: 409577162 Change-Id: Ieee709ff15c13bdd0b1d7598e27031867062b592 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6443776 Reviewed-by: David Baron <dbaron@chromium.org> Commit-Queue: Keith Cirkel <chromium@keithcirkel.co.uk> Commit-Queue: David Baron <dbaron@chromium.org> Auto-Submit: Keith Cirkel <chromium@keithcirkel.co.uk> Cr-Commit-Position: refs/heads/main@{#1446589}

This corresponds to a couple of spec changes: whatwg/html#10869 whatwg/dom#1341 The regressions are unfortunate and need looking into. The spec issues I've reported mostly have fixes PRed too. Just going to wait for those.

This corresponds primarily to these spec changes, plus a few follow-up spec fixes: whatwg/dom#1341 whatwg/html#10869 Still looking into the test regressions. Those might be spec issues but I'm currently assuming they're me issues. :^)

…egistry and custom-element-registry into registries, a=testonly Automatic update from web-platform-tests custom-elements: merge revamped-scoped-registry and custom-element-registry into registries And rename away from .tentative for the Revamped Scoped Custom Element Registry tests as whatwg/html#10869 and whatwg/dom#1341 are about to land. -- wpt-commits: 7087b359a1e2e306db934e5ff11218bd871cb228 wpt-pr: 51953

…ed registry, a=testonly Automatic update from web-platform-tests Scaffold out basic IDL for revamped scoped registry This implements the IDL definitions per the spec issue[1], however all methods are basic stubs and do not execute any logic - the logic will come with later patches. I2P: https://groups.google.com/a/chromium.org/g/blink-dev/c/um-9YjJWyEQ/m/MhKN0L7FAgAJ Spec PRs: HTML: whatwg/html#10869 DOM: whatwg/dom#1341 [1]: whatwg/html#10854 Bug: 409577162 Change-Id: Ieee709ff15c13bdd0b1d7598e27031867062b592 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6443776 Reviewed-by: David Baron <dbaron@chromium.org> Commit-Queue: Keith Cirkel <chromium@keithcirkel.co.uk> Commit-Queue: David Baron <dbaron@chromium.org> Auto-Submit: Keith Cirkel <chromium@keithcirkel.co.uk> Cr-Commit-Position: refs/heads/main@{#1446589} -- wpt-commits: 9546e2007adb73a3545fb61a5e5c8f754c6587e4 wpt-pr: 51977

…egistry and custom-element-registry into registries, a=testonly Automatic update from web-platform-tests custom-elements: merge revamped-scoped-registry and custom-element-registry into registries And rename away from .tentative for the Revamped Scoped Custom Element Registry tests as whatwg/html#10869 and whatwg/dom#1341 are about to land. -- wpt-commits: 7087b359a1e2e306db934e5ff11218bd871cb228 wpt-pr: 51953

…ed registry, a=testonly Automatic update from web-platform-tests Scaffold out basic IDL for revamped scoped registry This implements the IDL definitions per the spec issue[1], however all methods are basic stubs and do not execute any logic - the logic will come with later patches. I2P: https://groups.google.com/a/chromium.org/g/blink-dev/c/um-9YjJWyEQ/m/MhKN0L7FAgAJ Spec PRs: HTML: whatwg/html#10869 DOM: whatwg/dom#1341 [1]: whatwg/html#10854 Bug: 409577162 Change-Id: Ieee709ff15c13bdd0b1d7598e27031867062b592 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6443776 Reviewed-by: David Baron <dbaron@chromium.org> Commit-Queue: Keith Cirkel <chromium@keithcirkel.co.uk> Commit-Queue: David Baron <dbaron@chromium.org> Auto-Submit: Keith Cirkel <chromium@keithcirkel.co.uk> Cr-Commit-Position: refs/heads/main@{#1446589} -- wpt-commits: 9546e2007adb73a3545fb61a5e5c8f754c6587e4 wpt-pr: 51977

annevk mentioned this pull request Dec 17, 2024

Revamped Scoped Custom Element Registries #10854

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annevk marked this pull request as ready for review December 19, 2024 09:52

annevk added addition/proposal New features or enhancements topic: custom elements Relates to custom elements (as defined in DOM and HTML) topic: shadow Relates to shadow trees (as defined in DOM) labels Dec 19, 2024

annevk added a commit to whatwg/dom that referenced this pull request Dec 19, 2024

Add Scoped Custom Element Registries

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HTML PR: whatwg/html#10869. Tests: ... Closes #1339.

annevk force-pushed the annevk/scoped-custom-element-registries branch from ff4688a to 3ad2431 Compare December 19, 2024 10:07

This was referenced Jan 9, 2025

Upcoming WHATNOT meeting on 2025-01-09 #10878

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Upcoming WHATNOT meeting on 2025-01-16 #10906

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annevk commented Jan 31, 2025

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Add Scoped Custom Element Registries

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HTML PR: whatwg/html#10869. Tests: ... Closes #1339.

annevk force-pushed the annevk/scoped-custom-element-registries branch from 3ad2431 to 28bf12c Compare February 21, 2025 09:42

This was referenced Feb 21, 2025

Scoped Custom Element Registries mdn/content#38266

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Add Scoped Custom Element Registries whatwg/dom#1341

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Revamped Scoped Custom Element Registries #10854

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Revamped Scoped Custom Element Registries (DOM side) whatwg/dom#1339

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annevk force-pushed the annevk/scoped-custom-element-registries branch from f02797a to 98b171e Compare March 6, 2025 11:36

keithamus mentioned this pull request Mar 18, 2025

Scoped Custom Element Registries w3ctag/design-reviews#1070

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Scoped Custom Element Registries WebKit/standards-positions#38

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Add Scoped Custom Element Registries

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HTML PR: whatwg/html#10869. Tests: ... Closes #1339.

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Add Scoped Custom Element Registries

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DOM PR: whatwg/dom#1341. Tests: ... Closes #10854.

Address review feedback, add document's custom element registry

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annevk force-pushed the annevk/scoped-custom-element-registries branch from 8ef7c76 to 0bb0d3f Compare April 7, 2025 15:18

document invariant

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custom-elements: merge revamped-scoped-registry and custom-element-registry into registries web-platform-tests/wpt#51953

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annevk merged commit f2d8b88 into main Apr 14, 2025
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annevk added a commit to whatwg/dom that referenced this pull request Apr 14, 2025

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HTML PR: whatwg/html#10869. Tests: web-platform-tests/wpt#50790, web-platform-tests/wpt#50860, and web-platform-tests/wpt#51953. Closes #1339.

chromium-wpt-export-bot mentioned this pull request Apr 14, 2025

Scaffold out basic IDL for revamped scoped registry web-platform-tests/wpt#51977

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smaug---- mentioned this pull request Jun 13, 2025

Scoped Custom Elements Registries mozilla/standards-positions#424

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captainbrosset mentioned this pull request Jun 19, 2025

Add a feature for Scoped custom element registries web-platform-dx/web-features#3070

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Scoped custom element registries web-platform-tests/interop#1027

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smaug---- mentioned this pull request Mar 4, 2026

Window.customElements shouldn't change when initial about:blank is replaced with a loaded page? #12226

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		<p>To <dfn export>look up a custom element definition</dfn>, given null or a
		<code>CustomElementRegistry</code> object <var>registry</var>, string-or-null

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