It's a parctice that dates back to 2006 when the API was first written, and frankly isn't covered by the coding conventions. Same thing with the docblocks, they're all copypasted with some bits changed and don't even make sense if you look at them in the genereated code docs.
I don't feel that any of us depend on this anymore (get a better IDE), so in the inerest of consistancy it's time we said goodbye to it.
Code was largely copied from Tim's CR comment on r83812 but adapted to deal with the fact that we have to apply the cmcontinue-induced WHERE on cl_sortkey and cl_from only for the first query. Because ApiQueryBase doesn't let us unset or overwrite conditions like these in a nice way, I added an $extraQuery parameter to ApiQueryBase::select() that excepts additional query parameters that are only applied to that query but not stored in the object.
* Remove cl_type from paging in categorylinks - it's not
really needed there. Although cl_type is in WHERE but not
in ORDER BY clause the worst thing that can happen
is to have a filesort going again through <500 entries
selected by index. Or will FORCE INDEX work anyway?
* Revert schema change, as we don't need cl_type there
anyway (or even if we wanted to compare, it should
work as expected by using INT values against ENUM).
* Followup r80326: clarify description of type property
* Fix r80355: need to use addWhereRange() for the static ORDER BY on cl_type as well, to make sure it flips direction when needed (mixed-direction multi-field ORDER BYs are not indexed)
* Followup r80358: use current not previous value for cl_from, and use >= instead of > . This is the way continues are normally done
* Followup r80362: clarify description for sortkeyprefix property
* Introduced a "cache mode" concept to simplify the header generation code, and to avoid odd results when conflicting cache header requests are received from submodules, or at least to formalise the handling of such cases.
* Made the cache mode private by default, so that code written in ignorance of caching tends to be safe. If different query modules are used in a single request, private caching is preferred over public caching.
* Removed the "must-revalidate" option from all CC headers, this is really specific to page views with a hacked squid in front, I don't think it's applicable here.
* Made the watchlist module private. This is really the definition of private data. There's nothing in the HTTP spec that says the URL for a CC:public request is private and can't be leaked. CC:private provides protection against unknown proxy behaviour.
* In ApiQueryAllmessages: avoid calling $wgLang->getCode() to check if it's necessary to make a new $wgLang when lang= is specified, since this is the only thing that unstubs $wgUser.
* Removed "FIXME: should this check $user instead of $wgUser?" Answer is no.
