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3. Merge user labels with chart labels via a helper

Date: 2026-06-24

Status​

Accepted

Context​

Several objects combine the chart's labels with user-supplied labels (service.labels, ingress.labels, metrics.serviceMonitor.labels, etc.). The original approach emitted the chart labels and then appended the user map:

labels:
  {{- include "docker-registry.labels" . | nindent 4 }}
{{ toYaml .Values.service.labels | indent 4 }}

When a user set a key the chart also sets — most commonly release, the kube-prometheus-stack discovery label on a ServiceMonitor — this produced a duplicate YAML map key, which is invalid and was rejected by kubeconform and the API. This blocked the standard Prometheus-operator setup.

Decision​

Add docker-registry.labels.merged, which deep-merges a caller-supplied label map over the chart labels (user value wins) and emits a single map:

labels:
  {{- include "docker-registry.labels.merged" (dict "ctx" . "extra" .Values.service.labels) | nindent 4 }}

Used by Service, Ingress, HTTPRoute, ServiceMonitor, PodMonitor, PrometheusRule, Deployment, and StatefulSet.

Consequences​

  • Overriding a chart-set label collapses to one entry instead of producing invalid YAML.
  • The kube-prometheus-stack release discovery pattern works.
  • A unit test asserts the merged release label renders exactly once. The bug was originally caught by the static (kubeconform) test layer.