[prometheus] Error at installing alertmanager subchart

[joroitgix]

Describe the bug a clear and concise description of what the bug is.

Hello,
I have tryed to upgrade from helm chart 27.3.1 to 27.4.0, but receive the error below:

What's your helm version?

version.BuildInfo{Version:"v3.14.1", GitCommit:"e8858f8696b144ee7c533bd9d49a353ee6c4b98d", GitTreeState:"clean", GoVersion:"go1.21.7"}

What's your kubectl version?

Client Version: v1.30.0

Which chart?

27.4.0

What's the chart version?

27.4.0

What happened?

│ Error: YAML parse error on prometheus/charts/alertmanager/templates/ingress.yaml: error converting YAML to JSON: yaml: line 11: mapping values are not allowed in this context
│
│ with helm_release.prometheus,
│ on helm_prometheus.tf line 1, in resource "helm_release" "prometheus":
│ 1: resource "helm_release" "prometheus" {

What you expected to happen?

No response

How to reproduce it?

No response

Enter the changed values of values.yaml?

No response

Enter the command that you execute and failing/misfunctioning.

terraform apply -var-file=tfvars/prod.tfvars -target=helm_release.prometheus

Anything else we need to know?

No response

[zeritti]

There seems to be a bug introduced in the alertmanager chart 1.15.0 (used in prometheus 27.4.0) and that in the ingress labels (ingress.yaml):

labels:
  {{- include "alertmanager.labels" . | nindent 4 }}
  {{- if .Values.ingress.labels }}
  {{ toYaml .Values.ingress.labels | indent 4 }}
  {{- end }}

leading to the reported error if ingress.labels is set. The code should read

labels:
  {{- include "alertmanager.labels" . | nindent 4 }}
  {{- if .Values.ingress.labels }}
  {{- toYaml .Values.ingress.labels | nindent 4 }}
  {{- end }}