Code Generation: Non-Required Open Api 3.0 scalar properties are non nullable

I defined an Open API 3.0 spec with optional parameters. Optional parameters mean in my understanding, that they are nullable in C# and omitted in JSON serialization if they are null in C#.

But when I generate C# code, now the generated properties are never nullable, and I have no idea how to specify now not to serialize them. Am I doing something wrong or is this a major issue?

If I set the same spec to Open API 2.0, it behaves like I expect. The integers get generated as int? as I expect.

See this spec:

openapi: "3.0.0"
servers:
  - url: //petstore.swagger.io/v2
    description: Default server

components:
  schemas:
  
    Pet:
      type: object
      required:
        - id

      properties:
        id:
          type: integer
          
        id2:
          type: integer

Generated code:

//----------------------
// <auto-generated>
//     Generated using the NSwag toolchain v13.0.2.0 (NJsonSchema v10.0.20.0 (Newtonsoft.Json v11.0.0.0)) (http://NSwag.org)
// </auto-generated>
//----------------------


    [System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "10.0.20.0 (Newtonsoft.Json v11.0.0.0)")]
    public partial class Pet 
    {
        [Newtonsoft.Json.JsonProperty("id", Required = Newtonsoft.Json.Required.Always)]
        public int Id { get; set; }
    
        [Newtonsoft.Json.JsonProperty("id2", Required = Newtonsoft.Json.Required.DisallowNull, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public int Id2 { get; set; }
    
        private System.Collections.Generic.IDictionary<string, object> _additionalProperties = new System.Collections.Generic.Dictionary<string, object>();
    
        [Newtonsoft.Json.JsonExtensionData]
        public System.Collections.Generic.IDictionary<string, object> AdditionalProperties
        {
            get { return _additionalProperties; }
            set { _additionalProperties = value; }
        }
    
    
    }

I would like to send this Json as a response (set required id and leave out id2)

{
  "id" : 20
}

[timmvonputtkamer]

Okay, that looks like a good solution. Maybe GenerateOptionalPropertiesAsNullable is a better name for the setting?

[RicoSuter]

But yes you could argue that non-required properties also should be nullable and just ignored when null whereas nullable properties should serialize “null”, right?