HTML has a concept of states that don't map to a keyword, but each state must have a definition, the definition allows mapping back to a keyword, or null. As an example thepopover attribute has a missing value default ofno-popover state which let's the spec say things like "if the popover attribute is in the no-popover state".

Additionally, traditional enumerated attributes will map an invalid state back to a particular keyword; for examplepopover's invalid attribute state is themanual state, which maps to the keyword"manual". It's important to know what the invalid state maps back to because it determines what value is returned in the IDL for those values.

Note: not all missing values return null (e.g. thekind attribute on<track> elements has a missing value default of the subtitles state, so a track's.kind property returns"subtitles" even if the attribute is not present, another example is thetype attribute on<input> which defaults to"text").

With that said it's possible to be in "no state". In fact, an enumerated attribute without a missing value default will be in "no state", as will invalid. No state, AIUI, will always map to null.

So here, the simplest thing for us to do here, rather than the implied missing state is to remove this, and lean on thelack of a missing/invalid state returning the no state. IOW this line could simply be removed:

If you think missing the definitions create more ambiguity, then we can instead do something like:

The<tr> for the"undefined" keyword is missing a<th> to name its state. In other words there should be a line above L10848 with<th scope="row">Undefined</th>. (I cannot comment on L10848 sadly).

I don't think we want the missing value default here to return the Undefined state, that will mean the.ariaChecked property will return"undefined" whenaria-checked isn't on the element. I presume we want to returnnull instead? Browsers currently return null, so missing should be "no state", i.e. removed:

Partially fixed in new PR (spacing, but not missing value default):https://github.com/w3c/aria/pull/2484/files.

Looks like a mix of tabs/spaces here.

Fixed in new PR:#2484.

Again, here, the missing value default being theUndefined state means.ariaHasPopup will return"undefined" which I don't think is desirable. Instead: