CustomObjectsApi.getNamespacedCustomObject does not return metadata in the latest version of the client

[SachinHg]

Describe the bug
We use CustomObjectsApi to deal with the CRUD operations for istio related resources. Since upgrading the k8s client version to 20.0.1, the CustomObjectsApi.getNamespacedCustomObject does not return metadata as part of the response. This used to work in the older version of the client 1.12.

Client Version
20.0.1

Kubernetes Version
1.29

Java Version
Java 21

To Reproduce
Steps to reproduce the behavior:

public class CustomObjectResourceVersion {

public static void main(String[] args) {
    try {
        ApiClient client = Config.defaultClient();
        io.kubernetes.client.openapi.Configuration.setDefaultApiClient(client);

        CustomObjectsApi customObjectsApi = new CustomObjectsApi(client);

        String group = "networking.istio.io";
        String version = "v1beta1";
        String namespace = "default"; 
        String plural = "virtualservices";
        String name = "vs-name"; 

        Map<String, Object> customObject = (Map<String, Object>) customObjectsApi.getNamespacedCustomObject(
                group,
                version,
                namespace,
                plural,
                name
        );

       Gson gson = new Gson();
       String vsJsonString = gson.toJson(customObject);
       VirtualService existingVirtualService = gson.fromJson(vsJsonString, VirtualService.class);
      String resourceVersion = existingVirtualService.getMetadata().getResourceVersion();
} catch(Exception e) {
      e.printStackTrace();
}

}

Expected behavior
It should return the metadata.

Output of raw JSON

{\\\"group\\\":\\\"networking.istio.io\\\",\\\"version\\\":\\\"v1beta1\\\",\\\"namespace\\\":\\\"namespace-name\\\",\\\"plural\\\":\\\"virtualservices\\\",\\\"name\\\":\\\"example-virtualservice-name\\\"} \"}

[brendandburns]

Can you print the raw JSON object and attach it to this issue?

[brendandburns]

Additionally, can you try the 20.0.1-legacy version and see if that works?

[SachinHg]

@brendandburns updated the issue description with the raw json object. I can also confirm that this works without any problem with 20.0.1-legacy

[brendandburns]

For the raw JSON, I was hoping for the JSON that came back from the API server, not the JSON output of the client side object.

Can you provide the JSON from the server so that we can determine if there is some sort of parsing error?

For context, the code generator changed in the 20 release, which is likely the difference causing this, but I'm not certain exactly what is going wrong.