From @ANIRUDH-333 in Slack:

The main reason for adding support for custom labels in the GUAC Helm charts is to provide users with the flexibility to include labels that align with their organization's standards and requirements. In our case, when deploying the GUAC stack, we have certain organizational policies that require specific labels on all Kubernetes resources. Currently, we achieve this through patching, but having built-in support for custom labels would make this process more seamless and maintainable.

Thanks @ANIRUDH-333 for the PR.

The guac.labels helper function was intended for your use case and it should be included in all resources - https://github.com/kusaridev/helm-charts/blob/main/charts/guac/templates/_helpers.tpl#L38-L48

api-only-ingress.yaml:15:{{- include "guac.labels" . | nindent 4 }}
guacrest-service.yaml:11: {{- include "guac.labels" . | nindent 4 }}
ingestor-sa.yaml:15: {{- include "guac.labels" . | nindent 4 }}
oci-collector-deployment.yaml:14: {{- include "guac.labels" . | nindent 4 }}
guacrest-sa.yaml:15: {{- include "guac.labels" . | nindent 4 }}
cd-certifier-sa.yaml:15: {{- include "guac.labels" . | nindent 4 }}
graphql-server-deployment.yaml:14: {{- include "guac.labels" . | nindent 4 }}
ingestor-deployment.yaml:14: {{- include "guac.labels" . | nindent 4 }}
ingress.yaml:15:{{- include "guac.labels" . | nindent 4 }}
collectsub-deployment.yaml:14: {{- include "guac.labels" . | nindent 4 }}
depsdev-collector-deployment.yaml:14: {{- include "guac.labels" . | nindent 4 }}
guacrest-deployment.yaml:14: {{- include "guac.labels" . | nindent 4 }}
depsdev-collector-sa.yaml:15: {{- include "guac.labels" . | nindent 4 }}
collectsub-service.yaml:10: labels: {{- include "guac.labels" . | nindent 4 }}
oci-collector-sa.yaml:15: {{- include "guac.labels" . | nindent 4 }}
collectsub-sa.yaml:15: {{- include "guac.labels" . | nindent 4 }}
visualizer-deployment.yaml:14: {{- include "guac.labels" . | nindent 4 }}
ingest-guac-data-job.yaml:10: {{- include "guac.labels" . | nindent 4 }}
ingest-guac-data-job.yaml:20: {{- include "guac.labels" . | nindent 8 }}
graphql-server-service.yaml:11: {{- include "guac.labels" . | nindent 4 }}
graphql-server-service.yaml:36: {{- include "guac.labels" . | nindent 4 }}
osv-certifier-deployment.yaml:14: {{- include "guac.labels" . | nindent 4 }}
graphql-server-sa.yaml:15: {{- include "guac.labels" . | nindent 4 }}
osv-certifier-sa.yaml:15: {{- include "guac.labels" . | nindent 4 }}
visualizer-service.yaml:10: labels: {{- include "guac.labels" . | nindent 4 }}
cd-certifier-deployment.yaml:14: {{- include "guac.labels" . | nindent 4 }}

Perhaps move your guac.customLabels into guac.common.labels and drop a conditional and reference in guac.labels?
i.e.

{{/*
Common labels
*/}}
{{- define "guac.labels" -}}
helm.sh/chart: {{ include "guac.chart" . }}
{{ include "guac.selectorLabels" . }}

{{- if guac.common.labels }}
{{ include "guac.common.labels" . }}
{{- end }}

{{- if .Chart.AppVersion }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
{{- end }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}

Thanks, @sunnyyip, this is a better approach, we will try to make these changes and update the PR