How to INSERT/PREPEND an element into a JSON array using string(JSON)?

Code
1

Suppose that there is a JSON file (called array.json) with the following structure:

{
  "array":
  [
    {
      "name" : "element1",
      "property" : "value1"
    },
    {
      "name" : "element2",
      "property" : "value2"
    }
  ]
}

I wonder how to use string(JSON) command to:

  • INSERT a new element (element3) into the array between element1 and element2?
  • PREPEND a new element (element3) into the array?

BTW, I already know how to APPEND a new element (element3) into the array. The followings are my example codes:

Click to expand "json.cmake" 
file(READ "${CMAKE_CURRENT_LIST_DIR}/array.json" jsonCnt)

message("---------- array.json (before) ----------")
message("${jsonCnt}")

string(JSON arrayCnt GET "${jsonCnt}" "array")

message("---------- array (before) ----------")
message("${arrayCnt}")

# Create the 3rd element
set(newElemCnt "{}")
string(JSON newElemCnt SET "${newElemCnt}" "name"     "\"element3\"")
string(JSON newElemCnt SET "${newElemCnt}" "property" "\"value3\"")

# Append the 3rd element into the "array"
string(JSON arrayLen LENGTH "${arrayCnt}")
string(JSON arrayCnt SET "${arrayCnt}" ${arrayLen} "${newElemCnt}")

message("---------- array (after) ----------")
message("${arrayCnt}")

string(JSON jsonCnt SET "${jsonCnt}" "array" "${arrayCnt}")

message("---------- array.json (after) ----------")
message("${jsonCnt}")
Click to expand "array.json" 
{
  "array":
  [
    {
      "name" : "element1",
      "property" : "value1"
    },
    {
      "name" : "element2",
      "property" : "value2"
    }
  ]
}

After running the command cmake -P json.cmake in CLI, the output is:

Click to expand 
---------- array.json (before) ----------
{
  "array":
  [
    {
      "name" : "element1",
      "property" : "value1"
    },
    {
      "name" : "element2",
      "property" : "value2"
    }
  ]
}
---------- array (before) ----------
[
  {
    "name" : "element1",
    "property" : "value1"
  },
  {
    "name" : "element2",
    "property" : "value2"
  }
]
---------- array (after) ----------
[
  {
    "name" : "element1",
    "property" : "value1"
  },
  {
    "name" : "element2",
    "property" : "value2"
  },
  {
    "name" : "element3",
    "property" : "value3"
  }
]
---------- array.json (after) ----------
{
  "array" : 
  [
    {
      "name" : "element1",
      "property" : "value1"
    },
    {
      "name" : "element2",
      "property" : "value2"
    },
    {
      "name" : "element3",
      "property" : "value3"
    }
  ]
}

However, I just cannot figure out how to INSERT/PREPEND an element into the array. Is it possible to use the currently available subcommands (SET, GET, LENGTH, MEMBER…etc) of string(JSON) to implement these two operations?

If not, I would like to request the support for APPEND/INSERT/PREPEND subcommands of string(JSON).

2

Please don’t Cc maintainers on every question.

3

Got it. Sorry about that.

4

These do indeed seem to be missing operations. I think a feature request makes sense at least.