Untagged Attribute and options configurations don't seem to be working

[vitash]

I am writing an asp.net webapi program and in the setup section I added Services.AddJsonOptions( ... JsonFSharpOptions). The options is WithUnionInternalTag, which is used for default serialization. But for individual types, you need to use Untagged serialization. I found that [<JsonFSharpConverter(UnionEncoding=(JsonUnionEncoding.Untagged))>] Attribute doesn't seem to work.

Code version information:

    <TargetFramework>net8.0</TargetFramework>

    <PackageReference Include="FSharp.SystemTextJson" Version="1.2.42" />

Test Code:

[<JsonFSharpConverter(UnionEncoding=(JsonUnionEncoding.Untagged))>]
type Untagged1 = A of int | B of  string

[<Fact>]
let ``test tag`` () =
    let optInternalTag =
        JsonFSharpOptions()
                    .WithUnionInternalTag() // <-
                    .WithUnionAllowUnorderedTag()
                    .WithUnionUnwrapFieldlessTags()
                    .WithUnwrapOption()
                    .ToJsonSerializerOptions()

    let b = B "bbb"
    let jsonB = JsonSerializer.Serialize(b, optInternalTag)
    let valueB = JsonSerializer.Deserialize<Untagged1>("bbb", optInternalTag)

---

How should I configure it so that I can use options as the default serialization and Attribute as the individually specified serialization in an asp.net application?

[Tarmil]

.WithAllowOverride() should do what you need here.

[vitash]

Hi there, I've used other solutions before, and now that I've had time to continue testing the solution you mentioned WithAllowOverride, I've found that it doesn't work as expected either!

#r "nuget: FSharp.SystemTextJson, 1.3.13"

open System.Text.Json.Serialization
open System.Text.Json

[<JsonFSharpConverter(UnionEncoding=(JsonUnionEncoding.Untagged))>]
type Untagged1 = A of int | B of  string

let optInternalTag =
    JsonFSharpOptions()
        .WithUnionInternalTag() // <-
        .WithUnionAllowUnorderedTag()
        .WithUnionUnwrapFieldlessTags()
        .WithUnwrapOption()
        .WithAllowOverride() // add
        .ToJsonSerializerOptions()

let valB = B "bbb"
let jsonB = JsonSerializer.Serialize(valB, optInternalTag)
jsonB |> printfn "%A" // expect: jsonB = "bbb"; actual: jsonB = "{"Item":"bbb"}"

let valueB = JsonSerializer.Deserialize<Untagged1>("bbb", optInternalTag)
//  ^ System.Text.Json.JsonException: 'b' is an invalid start of a value. 
//           Path: $ | LineNumber: 0 | BytePositionInLine: 0.

This is a very nice library, thanks for the code!