includeTemplates doesn't work

[TobiasWillig]

Describe the bug

Labels aren't added to the pod metadata and the Deployment spec. includeTemplates has no effect.

Files that can reproduce the issue

kustomization.yaml

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
metadata:
  name: base-kustomization

commonLabels:
  app: test-server

labels:
  - pairs:
      app.kubernetes.io/name: test-server
      app.kubernetes.io/instance: test-server
      app.kubernetes.io/version: ${SERVER_VERSION}
      app.kubernetes.io/component: test
      app.kubernetes.io/part-of: test
      app.kubernetes.io/managed-by: test
      app.kubernetes.io/created-by: test
    includeTemplates: true

resources:
  - deployment.yaml

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: test-server
spec:
  replicas: 1
  template:
    metadata:
      name: test-server
    spec:
      restartPolicy: Always
      containers:
        - name: test-server
          image: test-server
          ports:
            - containerPort: 8080

Expected output

The Pod should have all defined labels from (commonLabels and labels).

Actual output

The Pod has only the labels from commonLabels.

Kustomize version

{Version:kustomize/v4.5.5 GitCommit:daa3e5e2c2d3a4b8c94021a7384bfb06734bcd26 BuildDate:2022-05-20T20:25:40Z GoOs:linux GoArch:amd64}

Platform

Ubuntu 20.04 LTS inside WSL

[KnVerey]

/triage accepted

As a workaround, the bug only seems to occur if the spec.template.metadata.labels does not exist in the first place. Even labels: {} will generate the expected behaviour (this is likely a clue as to what the fix needs to be).

@aibarbetta as the author of this feature, would you be able to look into this bug?

[aibarbetta]

/assign

[wolfmah]

The culprit is found here:

kustomize/api/internal/target/kusttarget_configplugin.go

Lines 289 to 292 in 5948f6a

	// merge spec/template/metadata fieldSpec if includeTemplate flag is true
	if label.IncludeTemplates {
	fss, err = fss.MergeOne(types.FieldSpec{Path: "spec/template/metadata/labels", CreateIfNotPresent: false})
	if err != nil {

The CreateIfNotPresent should be true. Though, I don't know if this would make side effect elsewhere. But, if we go by the logic found within commonLabels, it shouldn't be a problem:

kustomize/api/konfig/builtinpluginconsts/commonlabels.go

Lines 30 to 32 in d17ef91

	- path: spec/template/metadata/labels
	create: true
	kind: Deployment

As a bonus, the flag shouldn't be hardcoded to only spec/template/metadata/labels, but should include everything that is create: true from the commonLabels field specs: api/konfig/builtinpluginconsts/commonlabels.go