For any good reason I need to get more things in my Import Set response for REST interface. Ok, I just go to Transform map, use Explicit script, that script right in the transform map record, type there:
response.custom_element = "Welcome, REST response extension!";
and enJoy the Rest of the day! :)
Note, credits go to SN community. Stay brave!
Technical proof of the concept (there was no Rest some time ago)
The REST API comes to the stage
Note: The status_message and error_message fields on transformation scripts are processed and returned in response, along with any custom response fields.
// Load data from data source
var loader = new GlideImportSetLoader();
var importSetGr = loader.getImportSetGr(dataSource);
loader.loadImportSetTable(importSetRec, dataSource);
importSetGr.state = "loaded";
importSetGr.update();
// Run transformation
var transformWorker = new GlideImportSetTransformerWorker(importSetRec.sys_id, transformMapIDs);
transformWorker.setBackground(true);
transformWorker.start();
Credits: SN communite