.NET 8 - Newtonsoft.Json.JsonSerializationException: Error setting value to 'SelectedSwaggerGeneratorRaw' on 'NSwag.Commands.NSwagDocument'.

[jepperaskdk]

This bug seem similar to this, however I'm seeing this after upgrading from .NET 6 to .NET 8: #1576

Reproduce on a fresh API with no changes except nswag.json and adding nswag packages of 14.0.0-preview012. See this repository for a reproduce: https://github.com/jepperaskdk/nswagdotnet8

> dotnet "C:\Users\USER\.nuget\packages\nswag.msbuild\14.0.0-preview012\buildTransitive\../tools/Net80/dotnet-nswag.dll" run nswag.json
NSwag command line tool for .NET Core Net80, toolchain v14.0.0.0 (NJsonSchema v11.0.0.0 (Newtonsoft.Json v13.0.0.0))
Visit http://NSwag.org for more information.
NSwag bin directory: C:\Users\Jeppe\.nuget\packages\nswag.msbuild\14.0.0-preview012\tools\Net80

Executing file 'nswag.json' with variables ''...
Newtonsoft.Json.JsonSerializationException: Error setting value to 'SelectedSwaggerGeneratorRaw' on 'NSwag.Commands.NSwagDocument'.
 ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at NSwag.Commands.NSwagDocumentBase.set_SelectedSwaggerGeneratorRaw(JObject value) in /_/src/NSwag.Commands/NSwagDocumentBase.cs:line 88
   at Newtonsoft.Json.Serialization.ExpressionValueProvider.SetValue(Object target, Object value)
   --- End of inner exception stack trace ---

[jepperaskdk]

After cloning/running nswag locally, it fails on the same line:

var collectionProperty = SwaggerGenerators.GetType().GetRuntimeProperty(key[0].ToString().ToUpperInvariant() + key.Substring(1));

Where the key is "WebApiToOpenApiCommand"

SwaggerGenerators.Items has the following items:

{NSwag.Commands.IOutputCommand[3]}
    [0]: {NSwag.Commands.Generation.FromDocumentCommand}
    [1]: {NSwag.Commands.CodeGeneration.JsonSchemaToOpenApiCommand}
    [2]: {NSwag.Commands.Generation.AspNetCore.AspNetCoreToOpenApiCommand}

Any idea why it is missing WebApiToOpenApiCommand?
EDIT: I see now it is announced that WebApiToOpenApiCommand is deprecated and removed: #4524

[Ben555555]

@jepperaskdk I have the same issue. Do you know what the alternative is for "webApiToOpenApi" in nswag.json?

It says: "Removed WebApiToOpenApiCommand: Use the WebApiOpenApiDocumentGenerator to build your own CLI referencing controllers project to generate OpenAPI without starting the app" which links to https://github.com/RicoSuter/NSwag/wiki/WebApiOpenApiDocumentGenerator and there it says it's deprecated and links to https://github.com/RicoSuter/NSwag/wiki/AspNetCoreOpenApiDocumentGenerator where I cannot find any information how to change it. If I remove the documentGenerator from the nswag.json, it will build, but it will generate some random services with the code generator "openApiToTypeScriptClient".

When I use "aspNetCoreToOpenApi" for the document configuration it will start so many .NET processes that I will have to restart my computer.

I'm confused.

Edit: For now it seems to work for me like this, by setting noBuild = true:

{
  "runtime": "Net80",
  "defaultVariables": "Configuration=Debug",
  "documentGenerator": {
    "aspNetCoreToOpenApi": {
      "project": "MySolution.Api.csproj",
      "documentName": "v1",
      "msBuildProjectExtensionsPath": null,
      "configuration": null,
      "runtime": null,
      "targetFramework": null,
      "noBuild": true,
      "msBuildOutputPath": null,
      "verbose": true,
      "workingDirectory": null,
      "aspNetCoreEnvironment": null,
      "output": null,
      "newLineBehavior": "Auto"
    }
  },
  "codeGenerators": {
    "openApiToTypeScriptClient": {

But in my case I actually wouldn't need to run Program.cs which it seems to do. I only want to generate the client scripts...

[jepperaskdk]

@Ben555555 I have done the same, and I also experience the same issue with .NET processes being spawned, and as such I have had to disable generating the API clients on build (in csproj). EDIT: Setting "noBuild": true fixes it, as it still generates clients.

It might be a different issue however. For this issue, I suggest to throw a helpful error that "WebApiToOpenApiCommand" is not supported, rather than an obscure uncaught exception.

[MehdiElMellali]

I'm encountering a similar issue when migrating from .NET 6 to .NET 8 with NSwag. The error regarding 'WebApiToOpenApiCommand' removal and its alternatives resonates with what I'm experiencing. Have you found any further insights or workarounds since your last comment? I've tried adjusting configurations as suggested but still facing challenges. Any advice or updates on this matter would be greatly appreciated! Thanks in advance."