Make flat json array from nested one via JOLT

[#1]

Hi everyone!

I'm trying to flat array and it view as simple case, but I can't reach the goal.

Here is simple json input:

{
  "MainArray": {
    "mattr1": "some_value1",
    "mattr2": "some_value2",
    "Subarray": {
         "sattr1": 1,
         "sattr2": 2,
         "sattr3": 3
    }
  }
}

Then I would like to convert it to array of arrays [key, value],
Here is Desired Output:

{
  "ResultArray" : [ 
     [ "mattr1", "some_value1" ], 
     [ "mattr2", "some_value2" ], 
     [ "sattr1", 1 ], 
     [ "sattr2", 2 ], 
     [ "sattr1", 3 ] 
  ]
}

 Here is my spec:

[
  {
    "operation": "shift",
    "spec": {
      "MainArray": {
        "*": {
            "$": "ResultArray[#2][0]",
            "@": "ResultArray[#2][1]"
        },
        "Subarray": {
          "*": {
              "$": "ResultArray[#3][#2][0]",
              "@": "ResultArray[#3][#2][1]"
          }
        }
      }
    }
  }
]

 And I don't understand how to fix problem when Subarrays is inside extra array in my result:

{
  "ResultArray" : [ 
     [ "mattr1", "some_value1" ], 
     [ "mattr2", "some_value2" ], 
     [ 
        [ "sattr1", 1 ], 
        [ "sattr2", 2 ], 
        [ "sattr3", 3 ] 
     ] 
  ]
}

 Any advise, please.

[#2]

I'm not sure why your spec is producing this result, but to resolve it you can do the transformation on two shift operations: First to flatting json and move the subarray level to the root level and second to move the result and store it into an Array. Here is the spec I tried and it worked:

[
{
"operation": "shift",
"spec": {
"MainArray": {
"*": "ResultArray.&",
"Subarray": {
"*": "ResultArray.&"
}
}
}
},
{
"operation": "shift",
"spec": {
"ResultArray": {
"*": {
"$": "ResultArray[#2][0]",
"@": "ResultArray[#2][1]"
}
}
}
}
]

[#3]

@SAMSAL Thank for your variant, but it is not actually desired, because Subarray may be another structure of jolt rules inside for example like this

[
  {
    "operation": "shift",
    "spec": {
      "MainArray": {
        "*": {
            "$": "ResultArray[#2][0]",
            "@": "ResultArray[#2][1]"
        },
        "Subarray": {
          "*": {
              "$": "ResultArray[#3][#2][0]",
              "@": "ResultArray[#3][#2][1]",
              "#some_value": "ResultArray[#3][#2][3]"
          }
        }
      }
    }
  }
]

Btw it's my fault cause of not actually correct example (same rules for main and sub arrays)

[#4 · Accepted solution]

Actually it is not possible to solve this case in one shift - here is discussion and workaround with append subarray to mainarray.