patches is applied in different order than patchesJson6902

[ralgozino]

What happened?

tl;dr: while patchesJson6902 is applied after commonLabels (and labels), patches is applied before commonLabels and labels.

I was updating a kustomize v3.10.0 project to v5.6.0. The build was running fine and gave the same output with kustomize v5.6.0 than with v3.10.0, but I got a warning that patchesJson6902 and commonLabels were deprecated and I should update to patches and labels respectively.

After switching to the "new" patches and labels the output changed. A lot of debugging later, I realised that patches is applied after labels (and commonLabels) while patchesJson6902 is applied before labels (and commonLabels).

FYI: I did the migration first with kustomize edit fix and then manually just in case the automatic migration did something odd, but got the same result in both cases.

What did you expect to happen?

I expected that switching from patchesJson6902 to patches would give me the same result, as documented, but instead the output changed.

If this change in behaviour is by design it should be mentioned in the documentation. Current docs make you believe that switching from patchesJson6902 to patches is straight-forward (it is true for most cases)

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

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

labels:
  - pairs:
      my: value

patches:
  - target:
      kind: Pod
      version: v1
      name: myPod
    patch: |-
      - op: replace
        path: /metadata/labels
        value:
          patch: patches

#patchesJson6902:
#  - target:
#      kind: Pod
#      version: v1
#      name: myPod
#    patch: |-
#      - op: replace
#        path: /metadata/labels
#        value:
#          patch: patchesJson

#pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: myPod
spec:
  containers:
    - name: dummy
      image: dummy

Expected output

apiVersion: v1
kind: Pod
metadata:
  labels:
    patch: patchesJson
  name: myPod
spec:
  containers:
  - image: dummy
    name: dummy

Actual output

apiVersion: v1
kind: Pod
metadata:
  labels:
    my: value
    patch: patches
  name: myPod
spec:
  containers:
  - image: dummy
    name: dummy

The expected output is what you get if you comment the patches section and uncomment the patchesJson6902 section in the kustomization.yaml file above.

Kustomize version

5.6.10

Operating system

MacOS

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