csharp client generation using json and nswag or swagger codegen

[hanswright]

I have tried to generate a general client based on the yaml and json file but had issues
I verified it not to be tool limited .. (tried openapi-generator, codegen-cli and Nswag)

i.e. the cli tool gen command ..

npx @openapitools/openapi-generator-cli generate -i ./openapi.json -g csharp-netcore --additional-properties=targetFramework=netcoreapp3.1 -o ./weatherapi

this behaves similar on linux or windows (ubuntu 22.04LTS or windows10(latest))

QUESTION:
Has anyone successfully generated a csharp client with the given openapi.jason or openapi.yaml ?
If so please share details.

.. here is the nswag related exception using nswag studio (latest stable build)

Newtonsoft.Json.JsonSerializationException: Cannot populate JSON array onto type 'NJsonSchema.JsonSchema'. Path 'paths['/radar/servers'].get.responses.200.content['application/ld+json'].schema', line 1, position 21032.

Newtonsoft.Json.JsonSerializationException: Cannot populate JSON array onto type 'NJsonSchema.JsonSchema'. Path 'paths['/radar/servers'].get.responses.200.content['application/ld+json'].schema', line 1, position 21032.

Runtime: Default
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Populate(JsonReader reader, Object target)
at NJsonSchema.ExtensionDataDeserializationConverter.ReadJson(JsonReader reader, Type objectType, Object existingValue, JsonSerializer serializer)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.DeserializeConvertable(JsonConverter converter, JsonReader reader, Type objectType, Object existingValue)
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.PopulateDictionary(IDictionary dictionary, JsonReader reader, JsonDictionaryContract contract, JsonProperty containerProperty, 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.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.PopulateDictionary(IDictionary dictionary, JsonReader reader, JsonDictionaryContract contract, JsonProperty containerProperty, 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.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.Populate(JsonReader reader, Object target)
at NJsonSchema.ExtensionDataDeserializationConverter.ReadJson(JsonReader reader, Type objectType, Object existingValue, JsonSerializer serializer)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.DeserializeConvertable(JsonConverter converter, JsonReader reader, Type objectType, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
at NSwag.OpenApiPathItem.OpenApiPathItemConverter.ReadJson(JsonReader reader, Type objectType, Object existingValue, JsonSerializer serializer)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.DeserializeConvertable(JsonConverter converter, JsonReader reader, Type objectType, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateDictionary(IDictionary dictionary, JsonReader reader, JsonDictionaryContract contract, JsonProperty containerProperty, 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.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.Populate(JsonReader reader, Object target)
at NJsonSchema.ExtensionDataDeserializationConverter.ReadJson(JsonReader reader, Type objectType, Object existingValue, JsonSerializer serializer)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.DeserializeConvertable(JsonConverter converter, JsonReader reader, Type objectType, 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.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
at NJsonSchema.Infrastructure.JsonSchemaSerialization.FromJson[T](String json, IContractResolver contractResolver)
at NJsonSchema.Infrastructure.JsonSchemaSerialization.d__16`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at NSwag.OpenApiDocument.d__58.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at NSwag.OpenApiYamlDocument.d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at NSwag.Commands.Generation.FromDocumentCommand.d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at NSwag.Commands.Generation.FromDocumentCommand.d__8.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at NSwag.Commands.NSwagDocumentBase.d__41.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at NSwag.Commands.NSwagDocument.d__8.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at NSwag.Commands.Document.ExecuteDocumentCommand.d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at NSwag.Commands.Document.ExecuteDocumentCommand.d__8.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at NConsole.CommandLineProcessor.d__12.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at NConsole.CommandLineProcessor.d__11.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at NSwag.Commands.NSwagCommandProcessor.d__3.MoveNext()

[dwhitemv25]

Comparing the API files to the OpenAPI specification, it looks like the openapi.* files here are incomplete, or were generated incorrectly. The paths that generate errors from the code generator tools I've tested have invalid schema specifications for the responses. In particular, in the /radar/servers endpoint, the response schema is an empty array, which by the JSON Schema spec is not allowed; it must be an object or a boolean.

Running openapi.yaml through some OpenAPI validators throws heaps of errors in AlertCollection, so I suspect the generation scripts have problems. (or my validator has issues with deeply nested references.)

[cchild-atiba]

Loading the openapi.json in VS2022 and manually entering schema url: https://raw.githubusercontent.com/OAI/OpenAPI-Specification/main/schemas/v3.0/schema.json helped me locate and correct all the problems.

It was as simple as one find and replace all; also indicated in the screenshot.

[cchild-atiba]

As indicated by the schema validator, having the empty schema type be an [] (array) when the schema defines it as an object is a bug...
So if you download/update the 'openapi.json' file these steps would have to be performed again.

[cchild-atiba]

Though I should mention that there are other problems with this API that make this still a difficult problem for a strongly typed language that NSwag isn't ready to handle at least right now.

The generated class is going to have (over 1700) problems in .NET 6, at least when using the latest NuGet packages (Microsoft.Extensions.ApiDescription.Client 6.09, Newtonsoft.Json 13.0.1, & NSwag.ApiDescription.Client 13.16.1).

So if you're feeling up to massaging the generated client (and don't forget to make a copy that is retained) maybe it will save some time if you're going to use more than a few endpoints.

At first I was writing my own client using Refit and GeoJSON.Text...