The API has traditionally ignored values beyond the allowed limit,
returning a warning for this situation since 2008(!). It's long past time
for this error situation to actually raise an error, as requested in
https://phabricator.wikimedia.org/T41936.
This is happening in
https://gerrit.wikimedia.org/r/433742. It should be
deployed to Wikimedia wikis with 1.32.0-wmf.6 or later, see
https://www.mediawiki.org/wiki/MediaWiki_1.32/Roadmap for the schedule.
Logs indicate that few clients on Wikimedia wikis are hitting the warning.
You can check your client by seeing if you're receiving a "Too many values
supplied for parameter" warning, or by using Special:ApiFeatureUsage for
your client's user agent and looking for a "too-many-X" code.
If your client is affected, the solution is to divide the values into
batches of the appropriate size. Generally the limit is 50 values for
clients without the apihighlimits right and 500 for clients with that
right. The limits for any particular parameter are documented in the
auto-generated help and are available in machine-readable format via
action=paraminfo.
--
Brad Jorsch (Anomie)
Senior Software Engineer
Wikimedia Foundation