For loop expression index / context?

Hi, I was wondering if it is possible to get the index of the current item when doing some transformation inside a “for” expression?

For example for the input:

{ "rows" : [
{"name":"test"},
{"name":"test 2"}
]}

I would like to add row number entries like:

{ "rows" : [
{"name" : "test", "rowNo" : 1},
{"name" : "test 2", "rowNo" : 2}
]}

I was able to achieve this using functions like this (functions are borrowed from issue #122):

let rows = .rows

def index-of(array, value)
  find-index-of($array, $value, 0)

def find-index-of(array, value, index)
  if ($index >= size($array))
    -1
  else if ($array[$index] == $value)
    $index
  else
    find-index-of($array, $value, $index + 1)

{ "rows" : [ for (.rows) {
let rn = index-of($rows, .) + 1
"name":.name,
"rowNo": $rn
}]}

However, I wonder if there is a better way or if some variable (automatically set to proper value) could be added to for expression automatically to achieve same goal with simpler JSTL code, for example:

{ "rows" : [ for (.rows) {
"name":.name,
"rowNo": $forIdx + 1
}]}

Thanks 😃

[larsga]

Interestingly, SAP’s example integration uses zip and range to do exactly this: https://github.com/SAP-samples/cloud-workflow-samples/blob/master/cf-outlook-integration-sample/src/main/resources/com/sap/bpm/wfs/forms/adaptivecards/transform.jslt

Sounds like another vote in favour of either zip+range or zip-with-index

[larsga]

I kind of expected this feature request to show up at some point. I guess there are three main ways this could be done.

Range function as in Python

{ "rows" : [ for (range(size(.rows))) {
    "name" : .rows[.].name,
    "rowNo" : . + 1
}]}

Magic variable

That’s basically what you already showed.

Magic function

{ "rows" : [ for (.rows) {
    "name" : .name,
    "rowNo" : current-for-index() + 1
}]}

Opinions welcome.