Reference to undeclared resource

Question

Azure Loadbalancer Rule Module code is like below:

main.tf.

resource "azurerm_lb_rule" "lb_rule" {
  count                          = length(var.lb_rule_specs)
  name                           = var.lb_rule_specs[count.index]["name"]
  resource_group_name            = var.resource_group_name
  loadbalancer_id                = var.loadbalancer_id
  frontend_ip_configuration_name = var.lb_rule_specs[count.index]["frontend_ip_configuration_name"]
  protocol                       = var.lb_rule_specs[count.index]["protocol"]
  frontend_port                  = var.lb_rule_specs[count.index]["frontend_port"]
  backend_port                   = var.lb_rule_specs[count.index]["backend_port"]
  probe_id                       = var.probe_id
  load_distribution              = var.load_distribution
  backend_address_pool_id        = var.backend_address_pool_id
}

variables.tf

variable "lb_rule_specs" {
  description = "Load balancer rules specifications"
  type        = list(map(string))
}

variable "resource_group_name" {
  description = "Name of the resource group"
  type        = string
}

variable "loadbalancer_id" {
  description = "ID of the load balancer"
  type        = string
}

variable "backend_address_pool_id" {
  description = "Backend address pool id for the load balancer"
  type        = string
}

variable "probe_id" {
  description = "ID of the loadbalancer probe"
  type        = string
  default     = ""
}

variable "load_distribution" {
  description = "Specifies the load balancing distribution type to be used by the Load Balancer. Possible values are: Default – The load balancer is configured to use a 5 tuple hash to map traffic to available servers. SourceIP – The load balancer is configured to use a 2 tuple hash to map traffic to available servers. SourceIPProtocol – The load balancer is configured to use a 3 tuple hash to map traffic to available servers. Also known as Session Persistence, where the options are called None, Client IP and Client IP and Protocol respectively."
  type        = string
  default     = ""
}

Calling module as below:

variable "loadbalancer_rule" {
  description = "Map of loadbalancer-rule objects"
  type        = any
  default     = null
}

module "loadbalancer_rule" {
  for_each = coalesce(var.loadbalancer_rule, {})
  source   = "company.com.au/tfmodules/loadbalancer-rule/azurerm"
  version  = "7.0.0-2-1.0"

  backend_address_pool_id = try(each.value.backend_address_pool_id, null)
  load_distribution       = try(each.value.load_distribution, "")
  loadbalancer_id         = each.value.loadbalancer_ref != null ? module.loadbalancer[each.value.loadbalancer_ref].id : null
  probe_id                = each.value.probe_ref != null ? module.loadbalancer_probe[each.value.probe_ref].id : null
  resource_group_name     = var.__ngc.environment_resource_groups
  lb_rule_specs = [
    for lb_rule_spec in each.value.lb_rule_specs :
    {
      frontend_ip_configuration_name  = try(for_each.lb_rule_spec.frontend_ip_configuration_name, null)
      protocol                        = try(for_each.lb_rule_spec.protocol, null)
      frontend_port                   = try(for_each.lb_rule_spec.frontend_port, null)
      backend_port                    = try(for_each.lb_rule_spec.backend_port, null)
    }
  ]
}

lbrule.auto.tfvars.json file like below:

{
  "loadbalancer_rule": {
    "patterns_default_loadbalancer_rule": {
      "backend_address_pool_id": null,
      "lb_rule_specs" : {
        
          "name" : "test2",
          "protocol": "tcp",
          "frontend_port": "8080",
          "backend_port": "8081",
          "frontend_ip_configuration_name": "LBFrontendIPConfig_1"
      },
        "name" : "test2",
        "protocol": "tcp",
        "frontend_port": "8100",
        "backend_port": "9100",
        "frontend_ip_configuration_name": "LBFrontendIPConfig_2"
    
        },
      "load_distribution": "",
      "loadbalancer_ref": "patterns_default_loadbalancer",
      "probe_ref": "patterns_default_loadbalancer_probe"
    }
  }

Unfortunately, I get error as like below:

│ Error: Reference to undeclared resource
│
│   on loadbalancer_rule.tf line 20, in module "loadbalancer_rule":
│   20:       frontend_ip_configuration_name  = try(for_each.lb_rule_spec.frontend_ip_configuration_name, null)
│
│ A managed resource "for_each" "lb_rule_spec" has not been declared in the
│ root module.
╵
╷
│ Error: Reference to undeclared resource
│
│   on loadbalancer_rule.tf line 21, in module "loadbalancer_rule":
│   21:       protocol                        = try(for_each.lb_rule_spec.protocol, null)
│
│ A managed resource "for_each" "lb_rule_spec" has not been declared in the
│ root module.
╵
╷
│ Error: Reference to undeclared resource
│
│   on loadbalancer_rule.tf line 22, in module "loadbalancer_rule":
│   22:       frontend_port                   = try(for_each.lb_rule_spec.frontend_port, null)
│
│ A managed resource "for_each" "lb_rule_spec" has not been declared in the
│ root module.
╵
╷
│ Error: Reference to undeclared resource
│
│   on loadbalancer_rule.tf line 23, in module "loadbalancer_rule":
│   23:       backend_port                    = try(for_each.lb_rule_spec.backend_port, null)
│
│ A managed resource "for_each" "lb_rule_spec" has not been declared in the
│ root module.

I am guessing that I am not writing outer OR inner loop properly? or perhaps the definition file (variable file) is not right?

There could be one or more lb rules and for each of those there could be 1 or more front end ip, protocol, front end port and backend port.