When defining a custom modular input in an app, it is possible to design a custom user interface for setting up the parameters of that modular input. Some information on how to do this is available here:
https://docs.splunk.com/Documentation/Splunk/7.2.3/AdvancedDev/ModInputsCustomizeUI
That page shows an example XML definition that contains code that seems to generate GUI elements on the fly. For example this:
<key name="processValueEdit">[[ e for e in ['sourcetype'] if form_defaults.get(e) ][0]]</key>
I was unable to figure out how this works and couldn't find more documentation about it. Any hints where to find more information? Thanks!
This is now documented on dev.splunk.com: https://dev.splunk.com/enterprise/reference/modinputs/modinputsmanagerxml/
(sorry for the thread necromancy but I like to leave notes for others who stumble across the same questions)