Hello,

Here is an error that appeared with Moodle 2.9, consuming its webservices:

Moodle: 32877907 - The web service description parameter named 'userid' is an single or multiple structure. It can not be set as VALUE_OPTIONAL. Check web service description. | ERRORCODE: erroroptionalparamarray

The following error have been reported using RosarioSIS Moodle integrator:

Moodle integrator: error message from Moodle when trying to add a new subject

But also here on the forums: Developing a Web Service; Required Web Parameter missing even though it isn't declared? , XML-RPC Protocol problem

I myself confirm the error. Here are my remarks:

The message is unclear as it states the parameter userid even when the webservice function called does not need it.
The problem does not seem to be XML-RPC related but apparently affects all protocols.
The first mention of the problem I have found dates back from April 29.
It is pretty clear that the error is thrown here.

Related issue: MDL-46054 (see commits, it seems that every webservice function must be updated with DEFAULT instead of OPTIONAL!)