nodepool's node_pools_cgroup_mode is forced to be defined when setting any linux_node_config

[prune998]

TL;DR

I added values for node_pools_linux_node_configs_sysctls and the module was crashing with an error:

Call to function "coalesce" failed: no non-null, non-empty-string arguments.

at https://github.com/terraform-google-modules/terraform-google-kubernetes-engine/blob/v37.0.0/cluster.tf#L915

This is mainly due to the coalesce terraform function to expect at least one output not null or "" out of the choices.

Expected behavior

it should be possible to use any of the linux_node_config without being forced to create all (or some) of them.

Observed behavior

Call to function "coalesce" failed: no non-null, non-empty-string arguments.

when node_pools_cgroup_mode is unset, the expression at https://github.com/terraform-google-modules/terraform-google-kubernetes-engine/blob/v37.0.0/cluster.tf#L915 will all evaluate to null

 cgroup_mode = coalesce(local.node_pools_cgroup_mode[each.value["name"]], local.node_pools_cgroup_mode["all"], null)

Terraform Configuration

"node_pools_linux_node_configs_sysctls": {
  "all": {},
  "default-node-pool": {},
  "gke-shared-spot-c3st44": {}
}
"node_pools": [
  {
    "add_fallback": "true",
    "auto_repair": "true",
    "auto_upgrade": "true",
    "autoscaling": "true",
    "disk_size_gb": "100",
    "disk_type": "pd-balanced",
    "enable_gcfs": "true",
    "enable_secure_boot": "true",
    "image_type": "COS_CONTAINERD",
    "initial_node_count": "0",
    "instance_class": "n2d-standard;c3-standard",
    "is_dedicated": "true",
    "local_ssd_ephemeral_storage_count": "0",
    "location_policy": "ANY",
    "machine_type": "n2d-standard-32",
    "max_count": "2000",
    "max_pods_per_node": "110",
    "max_surge": "5",
    "min_count": "0",
    "name": "gke-shared-spot-n2dst32",
    "node_locations": "",
    "number": "32",
    "orig_name": "gke-shared-spot",
    "sizes": "32,48;44",
    "skip_on_demand": "true",
    "spot": "true"
  }
]

Terraform Version

Terraform v1.5.7
on darwin_arm64
+ provider registry.terraform.io/hashicorp/google v6.43.0
+ provider registry.terraform.io/hashicorp/kubernetes v2.37.1
+ provider registry.terraform.io/hashicorp/random v3.7.2

Terraform Provider Versions

+ provider registry.terraform.io/hashicorp/google v6.43.0
+ provider registry.terraform.io/hashicorp/kubernetes v2.37.1
+ provider registry.terraform.io/hashicorp/random v3.7.2

Additional information

module version 37.0.0