NSwag typescript model generation fails after upgrading to dotnet 8

Question

After upgrading from dotnet 7 to dotnet 8, nswag typescript model generation fails on my mac.

The following packages are installed:

<PackageReference Include="NSwag.AspNetCore" Version="14.0.1" />
<PackageReference Include="NSwag.MSBuild" Version="14.0.1">
    <PrivateAssets>all</PrivateAssets>
    <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
</PackageReference>

nswag.json looks like this:

{
  "runtime": "Net80",
  "documentGenerator": {
    "webApiToOpenApi": {
      "isAspNetCore": true,
      "defaultPropertyNameHandling": "CamelCase",
      "defaultReferenceTypeNullHandling": "NotNull",
      "defaultEnumHandling": "String",
      "assemblyPaths": [
        "bin/$(Configuration)/net8.0/MyProject.Web.Api.dll"
      ]
    }
  },
  "codeGenerators": {
    "openApiToTypeScriptClient": {
      "typeScriptVersion": 4.8,
      "dateTimeType": "Date",
      "nullValue": "Undefined",
      "generateClientClasses": false,
      "exceptionClass": "SwaggerException",
      "typeStyle": "Interface",
      "output": "../../../frontend/src/types/contracts/nswag-contracts.d.ts"
    }
  }
}

The csproj contains this:

<Target Name="NSwag" AfterTargets="Build">
    <Exec Command="$(NSwagExe_Net80) run nswag.json /variables:Configuration=$(Configuration)" />
</Target>

Compilation fails with the following error message:

Executing file 'nswag.json' with variables 'Configuration=Debug'...
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 ---
   at Newtonsoft.Json.Serialization.ExpressionValueProvider.SetValue(Object target, Object value)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.SetPropertyValue(JsonProperty property, JsonConverter propertyConverter, JsonContainerContract containerContract, JsonProperty containerProperty, JsonReader reader, Object target)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonSerializer.Deserialize(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
   at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
   at NSwag.Commands.NSwagDocumentBase.FromJson[TDocument](String filePath, String data) in /_/src/NSwag.Commands/NSwagDocumentBase.cs:line 222
   at NSwag.Commands.NSwagDocumentBase.LoadDocument[TDocument](String filePath, String data) in /_/src/NSwag.Commands/NSwagDocumentBase.cs:line 209
   at NSwag.Commands.NSwagDocumentBase.LoadAsync[TDocument](String filePath, String variables, Boolean applyTransformations) in /_/src/NSwag.Commands/NSwagDocumentBase.cs:line 203
   at NSwag.Commands.Document.ExecuteDocumentCommand.ExecuteDocumentAsync(IConsoleHost host, String filePath) in /_/src/NSwag.Commands/Commands/Document/ExecuteDocumentCommand.cs:line 64
   at NSwag.Commands.Document.ExecuteDocumentCommand.RunAsync(CommandLineProcessor processor, IConsoleHost host) in /_/src/NSwag.Commands/Commands/Document/ExecuteDocumentCommand.cs:line 33
   at NConsole.CommandLineProcessor.ProcessSingleAsync(String[] args, Object input)
   at NConsole.CommandLineProcessor.ProcessAsync(String[] args, Object input)
   at NSwag.Commands.NSwagCommandProcessor.ProcessAsync(String[] args) in /_/src/NSwag.Commands/NSwagCommandProcessor.cs:line 62
1>MyProject.Web.Api.csproj(37,9): Error MSB3073 : The command "dotnet "/Users/frank/.nuget/packages/nswag.msbuild/14.0.1/buildTransitive/../tools/Net80/dotnet-nswag.dll" run nswag.json /variables:Configuration=Debug" exited with code 255.
1>------- Finished building project: MyProject.Web.Api. Succeeded: False. Errors: 1. Warnings: 0

What’s wrong here? I haven’t touched the config files except for bumping the dotnet version from 7 to 8.

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