[Rendering] `merge` built-in function has different behavior between platforms

Target Platforms

Other

SDK Version

24.05

Application Name

None in particular

Problem Description

The result of merge function varies too much between WinUI3 and Designer:
If merge is done between the following JSONs:

• json_2

  {
      "test":{
          "val_1": 1
          "unique_1": true
      },
      "val_2": 1
  }
  

• json_2

  {
      "test":{
          "val_1": 2,
          "unique_2": true
      },
      "val_2": 2
  }
  

Issues found:

• Designer replaces all the nested JSONs (You can observe unique_1 and unique_2 are never present in the same merge result)
• WinUI3 does not replace values in nested JSONs (i.e. val_1 is always equal to the value of the first JSON)

Screenshots

No response

Card JSON

{
    "type": "AdaptiveCard",
    "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
    "version": "1.6",
    "$data": {
        "json_1":{
            "test":{
                "val_1": 1,
                "const_1": true
            },
            "val_2": 1
        },
        "json_2":{
            "test":{
                "val_1": 2,
                "const_2": true
            },
            "val_2": 2
        }
    },
    "body": [
        {
            "type": "TextBlock",
            "$data": "${merge(json_1, json_2)}",
            "text": "${jsonStringify($data)}",
            "wrap": true
        },
        {
            "type": "TextBlock",
            "$data": "${merge(json_2, json_1)}",
            "text": "${jsonStringify($data)}",
            "wrap": true
        }
    ]
}

Sample Code Language

No response

Sample Code

No response

Start by reproducing the supplied Adaptive Card with the merge built-in on Designer and WinUI3, then trace the separate rendering paths that evaluate merge. Compare both outputs with the expected nested-object merge behavior shown in the issue. Done means both platforms preserve unique keys and apply the later value for duplicate keys consistently.