[w3c/webcomponents] Let's make document.write()/open() throw during parser invocations of custom element constructors (#537)

Right now the spec says to make them silently do nothing. (Although there are some small bugs in how that's specced due to reusing existing machinery slightly wrong; see https://github.com/whatwg/html/issues/1630 and https://github.com/whatwg/html/issues/1603.) When working through this with @dominiccooney, I realized that it's probably more author-friendly to make these methods throw instead. I'm not sure why we didn't think of this before.

This is only for when the parser creates the custom element; it does not apply for `new XTag()` or `document.createElement("x-tag")`.

Does throwing sound good to everyone? @smaug----, @rniwa, @travisleithead

---
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/issues/537