On Sat, Mar 23, 2013 at 11:15 PM, Brad Jorsch <bjorsch(a)wikimedia.org> wrote:
It is documented that 'uccontinue' may be used
continuation, because all possible parameters to a module are
documented. But it is not documented anywhere that 'ucstart' might be
returned inside the query-continue node instead, even though this
could currently be the case (and note this is another candidate for
bug 24782 fixing).
Exactly - putting ucstart into query-continue was already a breaking
change whenever it was done, because the documentation states that
uccontinue is the parameter that is used for continues.
To fix the bug 24782, what is happening is essentially that the API is
going back to what it should have been doing all along, using e.g.
"uccontinue" for the continue parameter instead of "ucstart".
In general, if it is possible to use the existing, documented
parameter name, that will cause fewer problems than renaming it. In
particular, unless there is a maximum field length to worry about, it
seems like it should always be possible to honor the original
continuation parameter name for each module. That gives backwards
compatibility as long as the client treats the value as opaque data.
The documentation that the client should pass the entire
query-continue section is very recent  and was not at all part of
the original document API spec when it was introduced circa 2007.