Defining same port twice with multiple names gets reduced to one port

[Mangal-Nidhi]

trafficstars

What happened?

We want to define container port twice as below, with different names, so that same port can be referred by different names depending on the context.

containers:
     ports:
             - name: app
               containerPort: 9090
               protocol: TCP
            -  name: metrics
               containerPort: 9090
               protocol: TCP

This works with plain kubernetes. But after doing kustomize build output gets reduced to

containers:
     ports:
            - name: metrics
               containerPort: 9090
               protocol: TCP

Is this a bug or why there is a limitation to define the port only once?

Thanks, Nidhi

What did you expect to happen?

Expected both port names to be available in output.

How can we reproduce it (as minimally and precisely as possible)?

# kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- resources.yaml

# resources.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: test-object
data:
  placeholder: data

Expected output

containers:
     ports:
             - name: app
               containerPort: 9090
               protocol: TCP
            -  name: metrics
               containerPort: 9090
               protocol: TCP

Actual output

containers:
     ports:
            -  name: metrics
               containerPort: 9090
               protocol: TCP

Kustomize version

5.4.3

Operating system

Windows