Statefulset volumeClaimTemplates labels not properly merged after patch

[sylr]

What happened?

I encountered a case were label pairs are not properly merged after applying a patch.

What did you expect to happen?

I expected source labels pair to be still present in the volumeClaimTemplates[]/metadata/labels.

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

# source/kustomization
---
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- sts.yaml
labels:
- pairs:
    app.kubernetes.io/name: vmcluster
    app.kubernetes.io/stack: victoriametrics
  includeSelectors: true
  includeTemplates: true

# source/sts.yaml
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  labels:
    app.kubernetes.io/component: vmstorage
  name: vmstorage
spec:
  template:
    metadata:
      labels:
        app.kubernetes.io/component: vmstorage
    spec:
      containers:
      - name: vmstorage
        image: quay.io/victoriametrics/vmstorage:v1.128.0-cluster
  updateStrategy:
    rollingUpdate:
      partition: 0
    type: RollingUpdate
  volumeClaimTemplates:
  - apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      labels:
        app.kubernetes.io/component: vmstorage
      name: vmstorage-data
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 50Gi
      storageClassName: gp3
      volumeMode: Filesystem

# kustomization
---
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- source
labels:
- pairs:
    app.kubernetes.io/instance: vmcluster-internal
  includeSelectors: true
  includeTemplates: true
patches:
- path: patch.yaml

# patch.yaml
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  labels:
    app.kubernetes.io/component: vmstorage
  name: vmstorage
spec:
  volumeClaimTemplates:
  - apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      labels:
        app.kubernetes.io/component: vmstorage
      name: vmstorage-data
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 600Gi
      storageClassName: gp3
      volumeMode: Filesystem

Expected output

apiVersion: apps/v1
kind: StatefulSet
metadata:
  labels:
    app.kubernetes.io/component: vmstorage
    app.kubernetes.io/instance: vmcluster-internal
    app.kubernetes.io/name: vmcluster
    app.kubernetes.io/stack: victoriametrics
  name: vmstorage
spec:
  ...
  volumeClaimTemplates:
  - apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      labels:
        app.kubernetes.io/component: vmstorage
        app.kubernetes.io/instance: vmcluster-internal
        app.kubernetes.io/name: vmcluster
        app.kubernetes.io/stack: victoriametrics
      name: vmstorage-data
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 600Gi
      storageClassName: gp3
      volumeMode: Filesystem

Actual output

apiVersion: apps/v1
kind: StatefulSet
metadata:
  labels:
    app.kubernetes.io/component: vmstorage
    app.kubernetes.io/instance: vmcluster-internal
    app.kubernetes.io/name: vmcluster
    app.kubernetes.io/stack: victoriametrics
  name: vmstorage
spec:
  ...
  volumeClaimTemplates:
  - apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      labels:
        app.kubernetes.io/component: vmstorage
        app.kubernetes.io/instance: vmcluster-internal
      name: vmstorage-data
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 600Gi
      storageClassName: gp3
      volumeMode: Filesystem

Kustomize version

v5.7.1

Operating system

MacOS

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