Incorrect serialization using fsi and Newtonsoft on dotnet 6.0.3xx

[JonCanning]

Install dotnet 6.0.301 on Linux. I have tried Ubuntu and Debian on WSL.

sudo apt install dotnet-sdk-6.0

Run this script using dotnet fsi

#r "nuget:Newtonsoft.Json"

open Newtonsoft.Json

JsonConvert.SerializeObject {| x = 1 |}
|> printfn "%s"

or

type R = { x: int }
JsonConvert.SerializeObject { x = 1 } |> printfn "%s"

In either case output is

{"x@":1,"x":1}

Install 6.0.203

sudo apt install dotnet-sdk-6.0=6.0.203-1

output is

{"x":1}

Serialization is correct on Windows, and when using a regular class, only records in scripts are affected

Workaround

Use dotnet fsi --multiemit-

[dsyme]

@JonCanning Thank you.

As a workaround, using dotnet fsi --multiemit- makes the problem go away. You will lose debug symbols for scripts but that's all.

[dsyme]

The problem is related to this line:

fsharp/src/Compiler/CodeGen/IlxGen.fs

Line 2079 in 9df7080

ILMemberAccess.Public

which is active for multi-assembly emit.

There's a related line we need to check here: https://github.com/dotnet/fsharp/blob/main/src/Compiler/CodeGen/IlxGen.fs#L10675