How to configure JsonSchemaExporter for custom types?

[vengut]

For example: I setup a custom converter for ObjectId type

using MongoDB.Bson;
using System.Text.Json;
using System.Text.Json.Schema;
using System.Text.Json.Serialization;
using System.Text.Json.Serialization.Metadata;

JsonSerializerOptions serializerOptions = new(JsonSerializerOptions.Web)
{
    TypeInfoResolver = new DefaultJsonTypeInfoResolver(),
    Converters = { new JsonObjectIdConverter() },
};
JsonSchemaExporterOptions exporterOptions = new() { TreatNullObliviousAsNonNullable = true };

var schema = serializerOptions.GetJsonSchemaAsNode(typeof(Test), exporterOptions);
Console.WriteLine(schema);

file class Test
{
    public required ObjectId Id { get; set; }
    public required string Name { get; set; }
    public required bool Flag { get; set; }
}

file class JsonObjectIdConverter : JsonConverter<ObjectId>
{
    public override ObjectId Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
        => ObjectId.Parse(reader.GetString());

    public override void Write(Utf8JsonWriter writer, ObjectId value, JsonSerializerOptions options)
        => writer.WriteStringValue(value.ToString());
}

this just returns true for ObjectId type.
https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/extract-schema

{
  "type": "object",
  "properties": {
    "id": true,
    "name": {
      "type": "string"
    },
    "flag": {
      "type": "boolean"
    }
  },
  "required": [
    "id",
    "name",
    "flag"
  ]
}

[elgonzo]

Right now there isn't a public API for this. However, there is an API proposal to support scenarios like this: #105769. Basically, you either wait for this API to be realized in some form -- whenever this might be i don't know (it's currently a milestone for 10.0.0, but i am not involved with the .NET team and don't know how good the chances are for such a feature really becoming part of for the .NET 10 release), or you have to do this quasi "manually" using a TransformSchemaNode delegate, in which you somehow detect whether the property or the type of a property is being associated with one of your JsonConverters and then modify the Json schema for that property accordingly...