values -> yamlencode -> value between bracket are added between simple quote

[anthosz]

Terraform, Provider, Kubernetes and Helm Versions

Terraform version: 1.9.5
Provider version: 2.15.0
Kubernetes version: 1.30.0

Affected Resource(s)

• helm_release: prometheus
• helm_repository: https://prometheus-community.github.io/helm-charts

Terraform Configuration Files

resource "helm_release" "prometheus" {
  name             = "prometheus"
  repository       = "https://prometheus-community.github.io/helm-charts"
  chart            = "prometheus"
  namespace        = "monitoring"
  create_namespace = true
  timeout          = 600
  wait_for_jobs    = true
  values = [
    yamlencode({
      server = {
        remoteWrite = [{
          url                   = "http://1.1.1.1:9090/api/v1/write"
          write_relabel_configs = [{
            source_labels = "[__name__]"
            action        = "drop"
            regex         = "(.*_(duration_seconds|seconds_total|sizes)_bucket)"
          }]
        }]
      }
    }),
  ]

Steps to Reproduce

1. terraform apply

Expected Behavior

1. kubectl -n monitoring describe cm/prometheus-server | grep -A 4 1.1.1.1

- url: http://1.1.1.1:9090/api/v1/write
  write_relabel_configs:
  - action: drop
    regex: (.*_(duration_seconds|seconds_total|sizes)_bucket)
    source_labels: [__name__]

Actual Behavior

1. kubectl -n monitoring describe cm/prometheus-server | grep -A 4 1.1.1.1

- url: http://1.1.1.1:9090/api/v1/write
  write_relabel_configs:
  - action: drop
    regex: (.*_(duration_seconds|seconds_total|sizes)_bucket)
    source_labels: '[__name__]'

Description

The main issue is that when we use yamlencode and we complete a value by something between [ ], the string is included between simple quote. I tried also the trim function to force removal of these simple quote but no way.
If I check the plan or content in terraform.tfstate, there is no trace of simple quote, there is only double quote (string) like expected.
But once the configmap is created, this string is added between 2 simple quotes (that broke prometheus) and I don't understand what can explain this behavior :/

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