(In reply to comment #0)

This feature request has three logically related facets:

1. Hidden categories marked as HIDDENCAT should be marked as hidden in some

way, e.g. <cl ns="14" title="Category:Move protected" hidden=""/>. Sample query
is the URL for this bug. The current way of determining this is to get the text
of the category page or through list=allcategories (either way, a cumbersome
second query) because...

prop=categories doesn't mention hidden status, but it doesn't need to, because...

2. ... prop=categoryinfo doesn't mention hidden status either (sample query:

http://en.wikipedia.org/w/api.php?action=query&prop=categoryinfo&titles=Category:Move+protected).

...once bug 15191 is fixed, this will work, and you can use generator=categories&prop=categoryinfo

3. There should be an option to show/hide hidden categories on prop=categories,

e.g. clshow={nothidden,hidden,both}. The current behaviour is both, hidden
would return only hidden cats and nothidden only non-hidden cats.

That's the only remaining issue for this bug. It was fixed in r39504 (of course that won't work either until bug 15191 is fixed).