Throw exception for popovers/dialogs in non-active documents

concepts

1. Inactive doc throw

   showModal()/showPopover() on inactive documents throw InvalidStateError instead of silently no-oping. Surfaces bugs that previously slipped past.

2. error matrix

   Run all seven ways a dialog/popover lands in an inactive document — iframe, parseFromString, adopt-then-detach — and confirm each throws.

3. Iframe Popover Test

   Run each method — showPopover(), hidePopover(), togglePopover(), showModal(), close() — in both active and detached contexts. See exactly which throw InvalidStateError in Chrome 132+.

4. lifecycle traps

   Five real-world lifecycle scenarios where this throws: unloading tab, bfcache, detached iframe, navigation race, document.open(). Plus the canonical safe-show wrapper.

5. Iframe Document Tester

   Six test scenarios — active document, detached element, adopted element, dialog showModal, try/catch pattern, and active dialog — run live to confirm Chrome 132's NotSupportedError on inactive documents vs silent fail in older browsers.

why it shipped

This is a corner case change that hopefully does not impact developers. Previously calling `showPopover()` or `showModal()` on a popover or dialog that resides within an inactive document would silently fail. I.e. no exception would be thrown, but since the document is inactive, no popover or dialog would be shown. As of the https://github.com/whatwg/html/pu

references

• ChromeStatus entry
• Spec