@nicolaiarocci Thanks for filing this issue!

@eiriktsarpalis Is there a particular reason we opted not to generate schemas when ReferenceHandler.Preserve = true?

It seems like the schemas that Swashbuckle creates ignore the ReferenceHandler setting altogether:

"Person": {
        "type": "object",
        "properties": {
          "name": {
            "type": "string",
            "nullable": true
          },
          "child": {
            "$ref": "#/components/schemas/Person"
          },
          "parent": {
            "$ref": "#/components/schemas/Person"
          }
        },
        "additionalProperties": false
      },

for:

class Person
{
    public string? Name { get; set; }
    public Person? Child { get; set; }
    public Person? Parent { get; set; }
}

Reference preservation alters the schema for most types, notably with collections that end up wrapping their values in JSON objects. Support for it was cut in .NET 9 for lack of time, but it's conceivable that it could be added in the future provided there is demand.

I should add that enabling reference preservation in your app carries important security ramifications. It should only be used with trusted inputs produced by System.Text.Json. In my opinion, it is not appropriate to use reference preservation in the context of web apps or Open API.

I should add that enabling reference preservation in your app carries important security ramifications. It should only be used with trusted inputs produced by System.Text.Json. In my opinion, it is not appropriate to use reference preservation in the context of web apps or Open API.

Helo @eiriktsarpalis

I haven't understood well, I have that same error but also this one:
The depth of the generated JSON schema exceeds the JsonSerializerOptions.MaxDepth setting.

Could you help me understand why this happens and how to avoid it?

This looks like a different error. Could you file an issue in dotnet/runtime with a standalone reproduction? Thanks.