Github user ijokarumawak commented on the issue:
https://github.com/apache/nifi/pull/2777
As for Variable Registry, I think passing only FlowFile attribute is
enough, same as the way AbstractRecordProcessor is doing right now.
https://github.com/apache/nifi/blob/master/nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/AbstractRecordProcessor.java#L113
In that sense, I found a contradiction between current documentation and
behavior. Schema Name, Schema Version, Schema Branch and Schema Text are
documented that those supports Variable Registry and FlowFile Attributes, but
it can only access to FlowFile attributes. I assume this pattern is not
considered when ExpressionLanguageScope is added. Probably for another JIRA
(not filed yet).
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