update-variants error on 'random_id.name.*.hex' in node_pool

[skinlayers]

terraform v0.12.20

$ terraform providers
├── provider.google ~> 3.4
├── provider.google-beta ~> 3.4
├── provider.null ~> 2.1
├── provider.random ~> 2.2
├── module.cloud-nat
│   ├── provider.google (inherited)
│   └── provider.random (inherited)
├── module.gcp-network
│   ├── provider.google <4.0,>= 2.12
│   ├── module.routes
│       ├── provider.google <4.0,>= 2.12
│       └── provider.null (inherited)
│   ├── module.subnets
│       └── provider.google <4.0,>= 2.12
│   └── module.vpc
│       └── provider.google <4.0,>= 2.12
├── module.gke
│   └── module.gke
│       ├── provider.google (inherited)
│       ├── provider.google-beta >= 3.1, <4.0.0
│       ├── provider.kubernetes
│       ├── provider.null (inherited)
│       └── provider.random (inherited)
├── module.iap_bastion
│   ├── provider.google ~> 3.4
│   ├── provider.google-beta ~> 3.4
│   ├── provider.random (inherited)
│   ├── module.iap_tunneling
│       ├── provider.google (inherited)
│       └── provider.google-beta (inherited)
│   └── module.instance_template
│       └── provider.google (inherited)
├── module.project-factory_core_project_factory
│   ├── provider.google >= 2.1, < 4.0
│   ├── provider.google-beta >= 2.1, < 4.0
│   ├── provider.null ~> 2.1
│   ├── provider.random ~> 2.2
│   ├── module.gcloud_delete
│       ├── provider.null (inherited)
│       └── provider.random (inherited)
│   ├── module.gcloud_deprivilege
│       ├── provider.null (inherited)
│       └── provider.random (inherited)
│   ├── module.gcloud_disable
│       ├── provider.null (inherited)
│       └── provider.random (inherited)
│   └── module.project_services
│       └── provider.google >= 2.1, < 4.0
└── module.utils

From what I can tell, the splat doesn't work for accessing a map.
See: hashicorp/terraform#22476

Offending line:
https://github.com/terraform-google-modules/terraform-google-kubernetes-engine/blob/master/autogen/main/cluster.tf.tmpl#L341

Snippet:

# Based on https://github.com/terraform-google-modules/terraform-google-kubernetes-engine/blob/master/examples/safer_cluster/main.tf
resource "random_string" "suffix" {
  length  = 4
  special = false
  upper   = false
}

locals {
  resource_prefix = "foo"
  cluster_name = "bar-${local.resource_prefix}-gke-${random_string.suffix.result}"
}

module "gke" {
  source                 = "terraform-google-modules/kubernetes-engine/google//modules/safer-cluster-update-variant"
  version                = "~> 7.0.0"
  project_id             = data.google_client_config.default.project
  name                   = local.cluster_name
  regional               = true
  region                 = data.google_client_config.default.region
  network                = module.gcp-network.network_name
  subnetwork             = module.gcp-network.subnets_names[index(module.gcp-network.subnets_names, local.subnet_name)]
  ip_range_pods          = local.pods_range_name
  ip_range_services      = local.svc_range_name
  master_ipv4_cidr_block = "172.16.0.0/28"
  enable_private_endpoint = false
  skip_provisioners      = true

  master_authorized_networks = [
    {
      cidr_block   = "11.22.33.44/30"
      display_name = "foo-office-ip-range"
    },
  ]

  pod_security_policy_config = [{
    "enabled" = false
  }]
}

Error message:

Error: Unsupported attribute

  on .terraform/modules/gke/terraform-google-modules-terraform-google-kubernetes-engine-7be707a/modules/beta-private-cluster-update-variant/cluster.tf line 312, in resource "google_container_node_pool" "pools":
 312:   name     = random_id.name.*.hex[each.key]

This object does not have an attribute named "hex".


Error: Invalid index

  on .terraform/modules/gke/terraform-google-modules-terraform-google-kubernetes-engine-7be707a/modules/beta-private-cluster-update-variant/cluster.tf line 312, in resource "google_container_node_pool" "pools":
 312:   name     = random_id.name.*.hex[each.key]
    |----------------
    | each.key is "default-node-pool"
    | random_id.name is object with 1 attribute "default-node-pool"

The given key does not identify an element in this collection value: a number
is required.