Log message when invalidating record using "isEmpty"

[mbrodala]

The isEmpty transformation introduced with version 6.0 allows for dropping whole records in case a field is empty.

This is very useful but for debugging purposes and for giving feedback to the data source provider a message should be logged on every record which is dropped this way. This way it is rather easy to find the affected source records and fix them.

Right now we do this with a custom step which triggers a warning message in case a record is dropped. The record is added to the message as JSON encoded string.

[fsuter]

You're right, this would be useful. Any suggestion about error level? Warning? Notice?

[mbrodala]

Anything which is accessible at least from the log module should be fine. A cherry on the top would be a single warning in the module/CLI if there was at least one skipped record .

[fsuter]

The patch introduces logging using External Import's debug mechanism (at "error" level). So you need to activate the debug mode and set a proper logger configuration (for the Importer class). This is similar to the logging done when dropping a record from a user function by throwing the InvalidRecordException.

Last time I looked, entries written with TYPO3's logging system to the sys_log table were not compatible with the Log module, but I haven't checked if this has changed.

I'm not marking this issue as resolved, as I think that the cherry on top you mention is a worthwhile idea, but I would like to rework the messaging mechanism (also in relation to #179).