Display Ordering: will this cause open="" attributes to get removed during HTML parsing?

[domenic]

https://github.com/mfreed7/popup#display-ordering

It is possible for an HTML document to contain multiple elements with popup=popup. In this case, only the last such element on the page will remain open when the page is fully loaded. This is because each successive popup element will force the previous one closed via the “one at a time” behavior.

The implication of this, combined with https://github.com/mfreed7/popup#dismiss-behavior, is that at the end of parsing only a single open="" attribute will be present, and others will be removed.

If this is the case, it'd be good to call it out explicitly. Also, there is some worry about modifications to the DOM during parsing, and the associated events; see whatwg/html#4500 /cc @annevk @emilio. But probably it's no worse than custom elements, so I think that's not a real issue, just something we need to step lightly around...

[annevk]

Note that custom elements don't end up executing script in all documents they end up in, e.g., with XMLHttpRequest or DOMParser. The problem with <details open> is that it does, iirc.

[mfreed7]

I've moved this issue to here: openui/open-ui#494