<a> without href is not interactive content

[Ritsyy]

Fixes #168

[zcorpan]

Also need to change the element definition (<h4>The <dfn><code>a</code></dfn> element</h4>)

-   <dd><span>Interactive content</span>.</dd>
+   <dd>If the element has a <code data-x="attr-a-href">href</code> attribute: <span>Interactive content</span>.</dd>

Also images/content-venn.svg needs to change <code>a</code> to <code>a</code>* under Interactive.

Also Element content categories needs to change, move "a" on the Interactive row to the next column and add "(if the href attribute is present)".

Finally, as I mentioned in the bug, we will also need to change the content model of a to disallow a descendants. This could maybe be a separate commit. This similarly touches several parts of the spec.

[Ritsyy]

@zcorpan committed the changes, thanks for the reviews!

[zcorpan]

LGTM. Thanks! Do you also want to take a stab at

Finally, as I mentioned in the bug, we will also need to change the content model of a to disallow a descendants. This could maybe be a separate commit. This similarly touches several parts of the spec.

(Look at the footer element for an example.)

Otherwise I can do it.

[Ritsyy]

i would love to do it, if you could describe a little bit more. I saw the footer element but did'nt understood the scenario fully.

[zcorpan]

OK, so currently a's content model is

Content model:
Transparent, but there must be no interactive content descendant.

Since a without href is no longer interactive content, it would mean that it is allowed to nest <a>s, but it shouldn't be allowed. So the above should be

Content model:
Transparent, but there must be no interactive content or a element descendants.

I thought that other parts of the spec would need changing as well (content models section, the indexes) but upon closer inspection I think they are fine as-is.

[Ritsyy]

yes i was trying to find the other content model sections which needs to be altered, but i think only the element content model needs to be changed.

[zcorpan]

Merged as 528a223 -- thank you!