Make Attr inherit from Node again

[brettz9]

The inheritance of Attr from Node was added back. Please support (although nodeName exists as an alias, nodeType is not available, etc.).

[snuggs]

@domenic anyone working on this? If not can take a 🔪 at it.

[Robbert]

Last weekend I really needed Attr as Node again, and my attempted to do some refactoring turned out largely successful:
https://github.com/Robbert/jsdom/commits/issue-1641

I expect more work needs to be done to fully support Attr everywhere, in TreeWalker for example, I guess I should use annevk's commits to the DOM standard as checklist.

The main difficulty was the cyclic dependency of Node ⇒ attributes.js ⇒ Attr ⇒ Node, I noticed domenic ran into this issue earlier (#1247 (comment)). Since any type of Node usually is created through the Document, I chose to follow this pattern to remove the direct dependency of attibutes.js on Attr, and instead Attr is created through the ownerDocument of the ownerElement of the NamedNodeMap. This way no direct dependency on Attr is required.

Also, I'm registering all Node constructors on the Document implementation in a similar fashion as the custom element constructors for the HTML DOM are registered. See: Robbert@a62ec5d In another DOM implementation I worked on previously this approach worked splendidly.

If someone has time to give their opinion on this approach sometime, I can process the feedback and after that finish up details like TreeWalker support and updating the tests.

[snuggs]

1. @Robbert any way we can get this in a PR on your fork? Difficult to see the diffs.
2. Can you rebase the branch to reflect recent changes? Also will help with visibility.
   Looking good but need to pull down branch to diff. I know there are ways in github but just too lazy. 😁 Still should do 1, and 2 tho.

Please advise.

[Robbert]

@snuggs Definitely, wasn't sure if it was appropriate to send a pull request for work in progress. Will do so this week.

[chiptus]

any update on this? is it still in progress? or should I try to take it?

[chiptus]

is there any other node that will return nodeType undefined?

[Robbert]

@snuggs I just sent the pull request for my branch, sorry it took so long. This week I have plenty of time to look into the failing unit tests, but I prefer to only spend more time on this when the approach I took is acceptable.