Generated code does not compile when additionalProperties is not false

[KirkMunroSagent]

Describe the bug

When generating code from a yaml or json doc, where that doc does not explicitly specify that additionalProperties is false, and when the endpoint accepts an untyped object input, the generated code will not compile.

Version of NSwag toolchain, computer and .NET runtime used

This issue occurs with 14.13.0. I cannot update to 14.4.0 or 14.5.0 due to regressions introduced in those two releases.

To Reproduce

{
  "openapi": "3.0.1",
  "info": {
    "title": "My WebServices",
    "description": "My WebServices",
    "version": "1.0"
  },
  "servers": [
    {
      "url": "https://myservices.mysite.com/my-service"
    }
  ],
  "paths": {
    "/api/thing/createorupdate": {
      "post": {
        "tags": [],
        "summary": "/api/thing/createorupdate - POST",
        "operationId": "post-api-thing-createorupdate",
        "parameters": [
          {
            "name": "value",
            "in": "query",
            "schema": {
              "type": "object",
              "nullable": true
            }
          },
          {
            "name": "template",
            "in": "query",
            "schema": {
              "type": "string",
              "nullable": true
            }
          }
        ],
        "responses": {
          "200": {
            "description": "Success",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/ThingResponse"
                },
                "example": {
                  "status": 0,
                  "description": "string"
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "ThingResponse": {
        "type": "object",
        "properties": {
          "status": {
            "type": "integer",
            "format": "int32"
          },
          "description": {
            "type": "string",
            "nullable": true
          }
        }
      }
   },
    "securitySchemes": {
      "apiKeyHeader": {
        "type": "apiKey",
        "name": "My-Api-Key",
        "in": "header"
      }
    }
  },
  "security": [
    {
      "apiKeyHeader": [ ]
    }
  ]
}

The issue seems to occur because nswag recognizes that the input of type object is not a value type, and as a result it applies this code in the generated endpoint:

if (value != null)
{
    foreach (var item_ in value.AdditionalProperties)
    {
        urlBuilder_.Append(System.Uri.EscapeDataString(item_.Key)).Append('=').Append(System.Uri.EscapeDataString(ConvertToString(item_.Value, System.Globalization.CultureInfo.InvariantCulture))).Append('&');
    }
}

Since the object? value input is just an object and not a type defined in the json document, there is no AdditionalProperties property, and as a result the generated code does not compile.

Expected behavior

When generating a library when additionalProperties is either not provided (defaults to true) or is explicitly set to true, the code generator must not include code for appending AdditionalProperties on inputs of type object or object?.

Additional context

I think I've given enough detail to identify the issue. If not, let me know.

[KirkMunroSagent]

I should add, if I manually modify the json file to include additionalProperties: false in the schema section of the value parameter, then the code generates as expected, but in my case we have an automated workflow that exports the json and then creates the library, which should be possible with results that compile without having to script modifications to the json file.

e.g. If the value parameter is instead defined like this, it works:

          {
            "name": "value",
            "in": "query",
            "schema": {
              "type": "object",
              "nullable": true,
              "additionalProperties": false
            }
          }

That line for additionalProperties shouldn't be necessary though on a parameter of type object.

[KirkMunroSagent]

I think the issue is this code:

https://github.com/RicoSuter/NSwag/blob/9998913062e12ace779ad5ce0ad5fa5cbf2c1153/src/NSwag.CodeGeneration.CSharp/Models/CSharpParameterModel.cs#L52C1-L56C30

That appears to be missing an additional check, && Type != "object?". In my case, the parameter is nullable, and that seems to be what is throwing this off.

[lahma]

I think you have the pieces together here already so maybe you could create a PR with a fix and test coverage?

[KirkMunroSagent]

I think you have the pieces together here already so maybe you could create a PR with a fix and test coverage?

I could open a PR, and usually wouldn't hesitate to do so; however, I don't feel very encouraged when I open PR #4994 to fix a different issue, include tests, the PR builds fine, and then it just sits there with no comments or activity from project owners for over a year. Why would I spend time opening another when existing PRs seem to be primarily ignored?