kubernetes_resources datasource does not populate .objects.metadata for custom resourrces

[bburky]

I wanted to query for a Kubernetes custom resource across all namespaces, and while processing each I needed to know the namespace the resource it came from. However I discovered that metadata is not available in the output of the kubernetes_resources data source for (at least) custom resources. I tested with multiple unrelated custom resources and observed this. I only tested with the ConfigMap built in resource and noticed that it was present in the output though (I didn't test any other built in resources).

A minimal example to reproduce is below. This is simplified from my actual use case. Change api_version and kind in data.kubernetes_resources.customresources to match any CR that is present in your cluster for testing.

Terraform Version, Provider Version and Kubernetes Version

Terraform version: 1.5.7  (or Tofu v1.10.6)
Kubernetes provider version: v3.0.1
Kubernetes version: K3s v1.32.5+k3s1

Affected Resource(s)

• kubernetes_resources

Terraform Configuration Files

data "kubernetes_resources" "customresources" {
  api_version = "networking.istio.io/v1"
  kind        = "VirtualService"
}

data "kubernetes_resources" "configmaps" {
  api_version = "v1"
  kind        = "ConfigMap"
}

output "namespaces_with_customresources" {
  value = toset([ for customresource in data.kubernetes_resources.customresources.objects : customresource.metadata.namespace ])
}
output "namespaces_with_configmaps" {
  value = toset([ for configmap in data.kubernetes_resources.configmaps.objects : configmap.metadata.namespace ])
}

Steps to Reproduce

terraform init
terraform apply

Expected Behavior

Both built in Kubernetes resources and custom resources should populate .objects.metadata in their results. I only observed ConfigMaps populating this, but not my custom resource.

Actual Behavior

$ terraform plan
data.kubernetes_resources.customresources: Reading...
data.kubernetes_resources.configmaps: Reading...
data.kubernetes_resources.configmaps: Read complete after 0s
data.kubernetes_resources.customresources: Read complete after 0s

Changes to Outputs:
  + namespaces_with_configmaps = [
      + "default",
    ]

You can apply this plan to save these new output values to the Terraform state, without changing any real infrastructure.
╷
│ Error: Unsupported attribute
│ 
│   on main.tf line 12, in output "namespaces_with_customresources":
│   12:   value = toset([ for customresource in data.kubernetes_resources.customresources.objects : customresource.metadata.namespace ])
│ 
│ This object does not have an attribute named "metadata".
╵

Important Factoids

I tested with a couple different CRs. I didn't test with that many built-in k8s resources, maybe the issue is broader

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[bburky]

I actually misunderstood the current behavior when I created this issue, there may be a second or related bug:

The docs suggest you can leave namespace = empty to query all across all namespaces:
https://registry.terraform.io/providers/hashicorp/kubernetes/latest/docs/data-sources/resources#example-get-a-list-of-namespaces-excluding-kube-system-using-field_selector

However, it looks that only works for non-namespaced resources. For namespaced resources, it looks like a the null value ends up querying the default namespace only. The example above for data.kubernetes_resources.configmaps has this issue, it's a bug that namespaces_with_configmaps only returned default, I had ConfigMaps in many other namespaces.

I think querying all namespaces instead of default only would be the expected behavior here? The Kubernetes REST API supports this