Mason Freed

Thanks for raising this issue! Also thanks for [your analysis on SO](https://stackoverflow.com/questions/73283986/how-script-tag-forces-mutationobserver-to-run-early-in-declarative-shadow-dom), which I agree with. Per spec, the [clean up after running script](https://html.spec.whatwg.org/multipage/webappapis.html#clean-up-after-running-script) algorithm, step 3, says: 3. If...

> Fair enough, I opened https://bugzil.la/1784187 however I still believe this "Ensure observer runs" is quite obscure as to "how" it's supposed to do this, and "when" it does this....

@michaschwab can you elaborate on how often you think this pattern gets used on the web? Are there other, similar, "bulk" operations that we should also consider? There would seem...

> Is this the kind of evidence you are looking for? If you have questions, I can try to find more specific evidence. @michaschwab thanks for the terrific examples of...

I agree, and I didn’t miss that feedback. This change explicitly sets the “include shadow roots” flag to “deny”, so that XHR cannot be used to parse DSD content. Without...

> I missed that, is there a reason "deny" is not the default, given that it's "unsafe"? I'm open to suggestions on how I implemented this in the [HTML spec](https://github.com/whatwg/html/pull/5465/files)...

> Interesting, I guess I need to look at the specific PRs, but it seems that it could be a boolean everywhere that defaults to false, and when we invoke...

@josepharhar

Thanks to everyone for the great comments here. There seem to be a few themes - I'll try to summarize and respond: 1. What should the custom element definition look...

>> I agree that problem b) is a problem that needs a solution. Perhaps the parser could detect exactly-duplicate elements and condense them into a single CSSStyleSheet that gets added...