AllOf operator should not always create subclass

[Gh61]

Describe the bug

When using allOf (https://swagger.io/docs/specification/v3_0/data-models/oneof-anyof-allof-not/#allof) operator for combining $ref with description or example (eg. not extending the referenced type) NSwag generates subclass of the original reference type with generic name (and is not using the description for <summary> comment.).

Version of NSwag toolchain, computer and .NET runtime used

//
// Generated using the NSwag toolchain v14.4.0.0 (NJsonSchema v11.3.2.0 (Newtonsoft.Json v13.0.0.0)) (http://NSwag.org)
//

To Reproduce

Here is openapi specification with the issue

Open API with issue example

openapi: 3.0.4
info:
  title: Test Issue API
  version: 1.0.0
servers:
- url: https://localhost:44384/
  description: Main Server
tags:
- name: Test
  description: Actions for testing API availability.
paths:
  /v1/Test/Echo:
    post:
      summary: Used for checking API availability.
      operationId: Test-Echo
      tags:
      - Test
      requestBody:
        description: Request parameters
        required: true
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/EchoRequest"
      responses:
        200:
          description: Request completed successfully, response is provided.
          content:
            application/json:
              schema:
                allOf:
                - $ref: "#/components/schemas/EchoResponse"
                - example:
                    receivedText: Text
                    timeStamp: 1748596070
                    ok: true
components:
  schemas:
    UnixTimeStamp:
      type: integer
      format: int64
      description: Unix Timestamp (www.unixtimestamp.com) - number of seconds since 1.1.1970 0:00:00 UTC
      example: 1747924200
    EchoRequest:
      type: object
      description: Request for checking server availability.
      properties:
        Text:
          type: string
          nullable: true
          description: Text sent to API that will be returned in response.
      additionalProperties: false
    EchoResponse:
      type: object
      description: Server response for availability check.
      properties:
        Ok:
          type: boolean
          description: Flag indicating whether the request completed successfully.
        ReceivedText:
          type: string
          nullable: true
          description: Text that was sent in the request.
        TimeStamp:
          allOf:
          - $ref: "#/components/schemas/UnixTimeStamp"
          - description: Date and time when the response was generated

The result is here:

Generated C# code

//----------------------
// <auto-generated>
//     Generated using the NSwag toolchain v14.4.0.0 (NJsonSchema v11.3.2.0 (Newtonsoft.Json v13.0.0.0)) (http://NSwag.org)
// </auto-generated>
//----------------------

#pragma warning disable 108 // Disable "CS0108 '{derivedDto}.ToJson()' hides inherited member '{dtoBase}.ToJson()'. Use the new keyword if hiding was intended."
#pragma warning disable 114 // Disable "CS0114 '{derivedDto}.RaisePropertyChanged(String)' hides inherited member 'dtoBase.RaisePropertyChanged(String)'. To make the current member override that implementation, add the override keyword. Otherwise add the new keyword."
#pragma warning disable 472 // Disable "CS0472 The result of the expression is always 'false' since a value of type 'Int32' is never equal to 'null' of type 'Int32?'
#pragma warning disable 612 // Disable "CS0612 '...' is obsolete"
#pragma warning disable 649 // Disable "CS0649 Field is never assigned to, and will always have its default value null"
#pragma warning disable 1573 // Disable "CS1573 Parameter '...' has no matching param tag in the XML comment for ...
#pragma warning disable 1591 // Disable "CS1591 Missing XML comment for publicly visible type or member ..."
#pragma warning disable 8073 // Disable "CS8073 The result of the expression is always 'false' since a value of type 'T' is never equal to 'null' of type 'T?'"
#pragma warning disable 3016 // Disable "CS3016 Arrays as attribute arguments is not CLS-compliant"
#pragma warning disable 8600 // Disable "CS8600 Converting null literal or possible null value to non-nullable type"
#pragma warning disable 8602 // Disable "CS8602 Dereference of a possibly null reference"
#pragma warning disable 8603 // Disable "CS8603 Possible null reference return"
#pragma warning disable 8604 // Disable "CS8604 Possible null reference argument for parameter"
#pragma warning disable 8625 // Disable "CS8625 Cannot convert null literal to non-nullable reference type"
#pragma warning disable 8765 // Disable "CS8765 Nullability of type of parameter doesn't match overridden member (possibly because of nullability attributes)."

namespace MyNamespace
{
    using System = global::System;

    [System.CodeDom.Compiler.GeneratedCode("NSwag", "14.4.0.0 (NJsonSchema v11.3.2.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class Client 
    {
        #pragma warning disable 8618
        private string _baseUrl;
        #pragma warning restore 8618

        private System.Net.Http.HttpClient _httpClient;
        private static System.Lazy<Newtonsoft.Json.JsonSerializerSettings> _settings = new System.Lazy<Newtonsoft.Json.JsonSerializerSettings>(CreateSerializerSettings, true);
        private Newtonsoft.Json.JsonSerializerSettings _instanceSettings;

    #pragma warning disable CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider declaring as nullable.
        public Client(System.Net.Http.HttpClient httpClient)
    #pragma warning restore CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider declaring as nullable.
        {
            BaseUrl = "https://localhost:44384/";
            _httpClient = httpClient;
            Initialize();
        }

        private static Newtonsoft.Json.JsonSerializerSettings CreateSerializerSettings()
        {
            var settings = new Newtonsoft.Json.JsonSerializerSettings();
            UpdateJsonSerializerSettings(settings);
            return settings;
        }

        public string BaseUrl
        {
            get { return _baseUrl; }
            set
            {
                _baseUrl = value;
                if (!string.IsNullOrEmpty(_baseUrl) && !_baseUrl.EndsWith("/"))
                    _baseUrl += '/';
            }
        }

        protected Newtonsoft.Json.JsonSerializerSettings JsonSerializerSettings { get { return _instanceSettings ?? _settings.Value; } }

        static partial void UpdateJsonSerializerSettings(Newtonsoft.Json.JsonSerializerSettings settings);

        partial void Initialize();

        partial void PrepareRequest(System.Net.Http.HttpClient client, System.Net.Http.HttpRequestMessage request, string url);
        partial void PrepareRequest(System.Net.Http.HttpClient client, System.Net.Http.HttpRequestMessage request, System.Text.StringBuilder urlBuilder);
        partial void ProcessResponse(System.Net.Http.HttpClient client, System.Net.Http.HttpResponseMessage response);

        /// <summary>
        /// Used for checking API availability.
        /// </summary>
        /// <param name="body">Request parameters</param>
        /// <returns>Request completed successfully, response is provided.</returns>
        /// <exception cref="ApiException">A server side error occurred.</exception>
        public virtual System.Threading.Tasks.Task<Response> TestEchoAsync(EchoRequest body)
        {
            return TestEchoAsync(body, System.Threading.CancellationToken.None);
        }

        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
        /// <summary>
        /// Used for checking API availability.
        /// </summary>
        /// <param name="body">Request parameters</param>
        /// <returns>Request completed successfully, response is provided.</returns>
        /// <exception cref="ApiException">A server side error occurred.</exception>
        public virtual async System.Threading.Tasks.Task<Response> TestEchoAsync(EchoRequest body, System.Threading.CancellationToken cancellationToken)
        {
            if (body == null)
                throw new System.ArgumentNullException("body");

            var client_ = _httpClient;
            var disposeClient_ = false;
            try
            {
                using (var request_ = new System.Net.Http.HttpRequestMessage())
                {
                    var json_ = Newtonsoft.Json.JsonConvert.SerializeObject(body, JsonSerializerSettings);
                    var content_ = new System.Net.Http.StringContent(json_);
                    content_.Headers.ContentType = System.Net.Http.Headers.MediaTypeHeaderValue.Parse("application/json");
                    request_.Content = content_;
                    request_.Method = new System.Net.Http.HttpMethod("POST");
                    request_.Headers.Accept.Add(System.Net.Http.Headers.MediaTypeWithQualityHeaderValue.Parse("application/json"));

                    var urlBuilder_ = new System.Text.StringBuilder();
                    if (!string.IsNullOrEmpty(_baseUrl)) urlBuilder_.Append(_baseUrl);
                    // Operation Path: "v1/Test/Echo"
                    urlBuilder_.Append("v1/Test/Echo");

                    PrepareRequest(client_, request_, urlBuilder_);

                    var url_ = urlBuilder_.ToString();
                    request_.RequestUri = new System.Uri(url_, System.UriKind.RelativeOrAbsolute);

                    PrepareRequest(client_, request_, url_);

                    var response_ = await client_.SendAsync(request_, System.Net.Http.HttpCompletionOption.ResponseHeadersRead, cancellationToken).ConfigureAwait(false);
                    var disposeResponse_ = true;
                    try
                    {
                        var headers_ = new System.Collections.Generic.Dictionary<string, System.Collections.Generic.IEnumerable<string>>();
                        foreach (var item_ in response_.Headers)
                            headers_[item_.Key] = item_.Value;
                        if (response_.Content != null && response_.Content.Headers != null)
                        {
                            foreach (var item_ in response_.Content.Headers)
                                headers_[item_.Key] = item_.Value;
                        }

                        ProcessResponse(client_, response_);

                        var status_ = (int)response_.StatusCode;
                        if (status_ == 200)
                        {
                            var objectResponse_ = await ReadObjectResponseAsync<Response>(response_, headers_, cancellationToken).ConfigureAwait(false);
                            if (objectResponse_.Object == null)
                            {
                                throw new ApiException("Response was null which was not expected.", status_, objectResponse_.Text, headers_, null);
                            }
                            return objectResponse_.Object;
                        }
                        else
                        {
                            var responseData_ = response_.Content == null ? null : await response_.Content.ReadAsStringAsync().ConfigureAwait(false);
                            throw new ApiException("The HTTP status code of the response was not expected (" + status_ + ").", status_, responseData_, headers_, null);
                        }
                    }
                    finally
                    {
                        if (disposeResponse_)
                            response_.Dispose();
                    }
                }
            }
            finally
            {
                if (disposeClient_)
                    client_.Dispose();
            }
        }

        protected struct ObjectResponseResult<T>
        {
            public ObjectResponseResult(T responseObject, string responseText)
            {
                this.Object = responseObject;
                this.Text = responseText;
            }

            public T Object { get; }

            public string Text { get; }
        }

        public bool ReadResponseAsString { get; set; }

        protected virtual async System.Threading.Tasks.Task<ObjectResponseResult<T>> ReadObjectResponseAsync<T>(System.Net.Http.HttpResponseMessage response, System.Collections.Generic.IReadOnlyDictionary<string, System.Collections.Generic.IEnumerable<string>> headers, System.Threading.CancellationToken cancellationToken)
        {
            if (response == null || response.Content == null)
            {
                return new ObjectResponseResult<T>(default(T), string.Empty);
            }

            if (ReadResponseAsString)
            {
                var responseText = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
                try
                {
                    var typedBody = Newtonsoft.Json.JsonConvert.DeserializeObject<T>(responseText, JsonSerializerSettings);
                    return new ObjectResponseResult<T>(typedBody, responseText);
                }
                catch (Newtonsoft.Json.JsonException exception)
                {
                    var message = "Could not deserialize the response body string as " + typeof(T).FullName + ".";
                    throw new ApiException(message, (int)response.StatusCode, responseText, headers, exception);
                }
            }
            else
            {
                try
                {
                    using (var responseStream = await response.Content.ReadAsStreamAsync().ConfigureAwait(false))
                    using (var streamReader = new System.IO.StreamReader(responseStream))
                    using (var jsonTextReader = new Newtonsoft.Json.JsonTextReader(streamReader))
                    {
                        var serializer = Newtonsoft.Json.JsonSerializer.Create(JsonSerializerSettings);
                        var typedBody = serializer.Deserialize<T>(jsonTextReader);
                        return new ObjectResponseResult<T>(typedBody, string.Empty);
                    }
                }
                catch (Newtonsoft.Json.JsonException exception)
                {
                    var message = "Could not deserialize the response body stream as " + typeof(T).FullName + ".";
                    throw new ApiException(message, (int)response.StatusCode, string.Empty, headers, exception);
                }
            }
        }

        private string ConvertToString(object value, System.Globalization.CultureInfo cultureInfo)
        {
            if (value == null)
            {
                return "";
            }

            if (value is System.Enum)
            {
                var name = System.Enum.GetName(value.GetType(), value);
                if (name != null)
                {
                    var field = System.Reflection.IntrospectionExtensions.GetTypeInfo(value.GetType()).GetDeclaredField(name);
                    if (field != null)
                    {
                        var attribute = System.Reflection.CustomAttributeExtensions.GetCustomAttribute(field, typeof(System.Runtime.Serialization.EnumMemberAttribute)) 
                            as System.Runtime.Serialization.EnumMemberAttribute;
                        if (attribute != null)
                        {
                            return attribute.Value != null ? attribute.Value : name;
                        }
                    }

                    var converted = System.Convert.ToString(System.Convert.ChangeType(value, System.Enum.GetUnderlyingType(value.GetType()), cultureInfo));
                    return converted == null ? string.Empty : converted;
                }
            }
            else if (value is bool) 
            {
                return System.Convert.ToString((bool)value, cultureInfo).ToLowerInvariant();
            }
            else if (value is byte[])
            {
                return System.Convert.ToBase64String((byte[]) value);
            }
            else if (value is string[])
            {
                return string.Join(",", (string[])value);
            }
            else if (value.GetType().IsArray)
            {
                var valueArray = (System.Array)value;
                var valueTextArray = new string[valueArray.Length];
                for (var i = 0; i < valueArray.Length; i++)
                {
                    valueTextArray[i] = ConvertToString(valueArray.GetValue(i), cultureInfo);
                }
                return string.Join(",", valueTextArray);
            }

            var result = System.Convert.ToString(value, cultureInfo);
            return result == null ? "" : result;
        }
    }

    /// <summary>
    /// Request for checking server availability.
    /// </summary>
    [System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "14.4.0.0 (NJsonSchema v11.3.2.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class EchoRequest
    {
        /// <summary>
        /// Text sent to API that will be returned in response.
        /// </summary>
        [Newtonsoft.Json.JsonProperty("Text", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public string Text { get; set; }

    }

    /// <summary>
    /// Server response for availability check.
    /// </summary>
    [System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "14.4.0.0 (NJsonSchema v11.3.2.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class EchoResponse
    {
        /// <summary>
        /// Flag indicating whether the request completed successfully.
        /// </summary>
        [Newtonsoft.Json.JsonProperty("Ok", Required = Newtonsoft.Json.Required.DisallowNull, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public bool Ok { get; set; }

        /// <summary>
        /// Text that was sent in the request.
        /// </summary>
        [Newtonsoft.Json.JsonProperty("ReceivedText", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public string ReceivedText { get; set; }

        [Newtonsoft.Json.JsonProperty("TimeStamp", Required = Newtonsoft.Json.Required.DisallowNull, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
        public TimeStamp TimeStamp { get; set; }

        private System.Collections.Generic.IDictionary<string, object> _additionalProperties;

        [Newtonsoft.Json.JsonExtensionData]
        public System.Collections.Generic.IDictionary<string, object> AdditionalProperties
        {
            get { return _additionalProperties ?? (_additionalProperties = new System.Collections.Generic.Dictionary<string, object>()); }
            set { _additionalProperties = value; }
        }

    }

    [System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "14.4.0.0 (NJsonSchema v11.3.2.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class Response : EchoResponse
    {

    }

    [System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "14.4.0.0 (NJsonSchema v11.3.2.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class TimeStamp : long
    {

    }



    [System.CodeDom.Compiler.GeneratedCode("NSwag", "14.4.0.0 (NJsonSchema v11.3.2.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class ApiException : System.Exception
    {
        public int StatusCode { get; private set; }

        public string Response { get; private set; }

        public System.Collections.Generic.IReadOnlyDictionary<string, System.Collections.Generic.IEnumerable<string>> Headers { get; private set; }

        public ApiException(string message, int statusCode, string response, System.Collections.Generic.IReadOnlyDictionary<string, System.Collections.Generic.IEnumerable<string>> headers, System.Exception innerException)
            : base(message + "\n\nStatus: " + statusCode + "\nResponse: \n" + ((response == null) ? "(null)" : response.Substring(0, response.Length >= 512 ? 512 : response.Length)), innerException)
        {
            StatusCode = statusCode;
            Response = response;
            Headers = headers;
        }

        public override string ToString()
        {
            return string.Format("HTTP Response: \n\n{0}\n\n{1}", Response, base.ToString());
        }
    }

    [System.CodeDom.Compiler.GeneratedCode("NSwag", "14.4.0.0 (NJsonSchema v11.3.2.0 (Newtonsoft.Json v13.0.0.0))")]
    public partial class ApiException<TResult> : ApiException
    {
        public TResult Result { get; private set; }

        public ApiException(string message, int statusCode, string response, System.Collections.Generic.IReadOnlyDictionary<string, System.Collections.Generic.IEnumerable<string>> headers, TResult result, System.Exception innerException)
            : base(message, statusCode, response, headers, innerException)
        {
            Result = result;
        }
    }

}

#pragma warning restore  108
#pragma warning restore  114
#pragma warning restore  472
#pragma warning restore  612
#pragma warning restore 1573
#pragma warning restore 1591
#pragma warning restore 8073
#pragma warning restore 3016
#pragma warning restore 8600
#pragma warning restore 8602
#pragma warning restore 8603
#pragma warning restore 8604
#pragma warning restore 8625

See the 2 unexpected classes:

• public partial class Response : EchoResponse
• public partial class TimeStamp : long

Expected behavior

1. In both cases it should not create new class (when no new properties are defined or any behaviour is changed)
2. It should take the description from allOf operator and use it for property <summary> comment