Selection should not retain attributes after parent block removal by an external change

[oleq]

1. Go to http://localhost:8125/ckeditor5-link/tests/manual/tickets/113/1.html.
2. Take the 2nd scenario.
3. Write some text.

Expected:

The selection should not retain previous (linkHref) attribute. The whole editing context has changed and most likely users will not expect that.

Actual:

Still writing in the same link despite that it's parent paragraph has been removed from the model.

Spotted in ckeditor/ckeditor5-link#165.

Note: It's not about the link. Other attributes like bold, etc. are also retained.

[Reinmar]

This is weird. cc @scofalik @pjasiun

[pjasiun]

That's definitely a bug. This is because selection attributes are updated only as the result of selection operations:

https://github.com/ckeditor/ckeditor5-engine/blob/6d0c555c0a6da4e0aad9786aa50b6258bd8c51ad/src/model/documentselection.js#L486-L488

This makes sense for attribute define "manually". If I click the bold button I don't want to lose this attribute because of external change (which may even not touch my selection). It should, apparently, behave differently for attributes which are set based on the surrounding text. We already distinguish these types of attributes using the attribute priority.

BTW: attributes priorities should be better described, now it's hard to learn what some parts of the code do.