JSON.Net serializer adds duplicate "field@" record fields in FSI (SDK version 6.0.300+)

[HoraceGonzalez]

Json.NET serialization of records adds duplicate fields with @ appended to the name in FSI (SDK versions 6.0.300 and up). For example, serializing this anonymous record:

JsonConvert.SerializeObject {| foo = "bar" |}

produces this result:

{"foo@":"bar","foo":"bar"}

Repro steps

Provide the steps required to reproduce the problem:

1. Install SDK version 6.0.302
2. create a new project folder, eg. mkdir temp
3. add a new global.json` with the following content:

   {
   "sdk": {
     "version": "6.0.302"
   }
   }

4. create a new temp/test.fsx file with the following content:

   #r "nuget: Newtonsoft.Json, 13.0.1"
   
   open System
   open Newtonsoft.Json
   
   JsonConvert.SerializeObject {| foo = "bar" |}
   |> printfn "%s"

5. execute the script using cd temp && dotnet fsi test.fsx

Expected behavior

stdout prints:

{"foo":"bar"}

Actual behavior

stdout prints:

{"foo@":"bar","foo":"bar"}

Known workarounds

Change the sdk version to 6.0.107. I also observed the issue in 6.0.300

Related information

dotnet --info output below

.NET SDK (reflecting any global.json):
 Version:   6.0.302
 Commit:    c857713418

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  22.04
 OS Platform: Linux
 RID:         ubuntu.22.04-x64
 Base Path:   /home/tracy/.dotnet/sdk/6.0.302/

global.json file:
  /home/tracy/code/fsi-test/global.json

Host:
  Version:      6.0.7
  Architecture: x64
  Commit:       0ec02c8c96

.NET SDKs installed:
  6.0.107 [/home/tracy/.dotnet/sdk]
  6.0.300 [/home/tracy/.dotnet/sdk]
  6.0.302 [/home/tracy/.dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 6.0.5 [/home/tracy/.dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.7 [/home/tracy/.dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.5 [/home/tracy/.dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.7 [/home/tracy/.dotnet/shared/Microsoft.NETCore.App]

Download .NET:
  https://aka.ms/dotnet-download

Learn about .NET Runtimes and SDKs:
  https://aka.ms/dotnet/runtimes-sdk-info

• Editing Tools: vscode/ionide

[HoraceGonzalez]

Attached a sample project that reproduces the issue on my machine: issue-13546-repro.zip

Note, running the project w/t dotnet run . seems to work. The issue only seems to happen in FSI. I've tested using paket as well.

[vzarytovskii]

Duplicate of https://github.com/dotnet/fsharp/issues/13493