How to remove a null element from an array using the Jolt Transformation specification?

Question

I want to remove null elements from the array using the Jolt spec.

Example:

Input:

{
  "arrayOne": [
    null,
    {
      "key1": "value1",
      "key2": "value2"
    }
  ]
}

Required output:

{
  "arrayOne": [
    {
      "key1": "value1",
      "key2": "value2"
    }
  ]
}

I tried using "recursivelySquashNulls" but that did not work.

[
  {
    "operation": "modify-overwrite-beta",
    "spec": {
      "*": "=recursivelySquashNulls"
    }
  }
]

Answer 1

You can use the following shift transformations in first of which the related nodes are taken without square brackets, eg. &2, &1, & such as :

[
  {
    "operation": "shift",
    "spec": {
      "*": {
        "*": {
          "*": "&2.&1.&" //&2 represents the literal "arrayOne"
                         //&1 represents the indexes of the wrapper array "arrayOne"
                         //&  represents the values of the leaf nodes
        }
      }
    }
  },
  {
    "operation": "shift",
    "spec": {
      "*": {
        "*": "&1[]"
      }
    }
  }
]

the demo on the site https://jolt-demo.appspot.com/ is :