Reference Target for Cross-Root ARIA

Description

After recieving 82 👍 12 ❤️ and 9 🚀 emojis from last year's interop proposal (#1011), I'm once again asking for Reference Target to be considered for Interop 2027. It solves (and doesn't solve) some long standing issues with cross-root associations as outlined in the Edge Demo for Reference Target.

• Reference Target has an Intent to Ship in Chromium 152
• All browsers have an implementation with passing tests behind a flag (WPT.fyi)
• There's a community attempt at polyfilling the behavior: https://westbrook.github.io/reference-target-polyfill/

While I personally wish that "Attribute forwarding" as called out in the Edge demo could be reconsidered, I think anything we could do to solve this gap would be a huge leap forward in component authoring.

Specification

WHATWG

web-feature

referencetarget

Test Links

• https://github.com/web-platform-tests/wpt/tree/master/shadow-dom/reference-target/tentative
• https://wpt.fyi/results/shadow-dom/reference-target/tentative?label=experimental&label=master&aligned

Additional Signals

• Edge: Intent to Experiment https://groups.google.com/a/chromium.org/g/blink-dev/c/C3pELgMqzCY/m/DzCzBHPcAQAJ
• Edge: Intent to Ship https://groups.google.com/a/chromium.org/g/blink-dev/c/eBx3sXIfJnw/m/TZgxd6uQAQAJ
• Gecko: No signal (https://github.com/mozilla/standards-positions/issues/1035)
• WebKit: No signal (https://github.com/WebKit/standards-positions/issues/356)

Start with the Edge Demo for Reference Target and the tentative Web Platform Tests under shadow-dom/reference-target/tentative, then compare the linked WPT.fyi results and browser signals. The issue is a request for Interop consideration rather than a scoped code change, so done is not defined; a concrete test or implementation task would need to be identified first.