Taken over from ZBX-17411 ...

It would be great to have a preprocessor which can catch ZBX_NOTSUPPORTED and set another value instead. Like it's currently already available for the custom errors preprocessor.

A use-case would be for example the kind of wrong result given on a missing directory in vfs.dir.size. If the dir is missing ZBX_NOTSUPPORTED is returned which is in fact just wrong. The message states correctly that the dir is missing but the notsupported counts toward the zabbix internal metric for unsupported items - which is crucial to monitor! - and thus is producing false-positives. There are some other items which behaves the same.

A new preprocessor or a modified custom error which could catch the ZBX_NOTSUPPORTED could transform the state to whatever value the user likes.

For example: on a missing vfs.dir.size I would modify the pre-processor to catch the ZBX_NOTSUPPORTED (maybe with further filtering the exact error message?) and instead setting the value to 0. Thus I could also build triggers like ".last() = 0 then" or ".last() > 0 then".