fix: Change subnets default value to null (#341)

Author: andyli

README.md

@@ -419,7 +419,7 @@ No modules.
 | <a name="input_security_group_use_name_prefix"></a> [security\_group\_use\_name\_prefix](#input\_security\_group\_use\_name\_prefix) | Determines whether the security group name (`security_group_name`) is used as a prefix | `bool` | `true` | no |
 | <a name="input_security_groups"></a> [security\_groups](#input\_security\_groups) | A list of security group IDs to assign to the LB | `list(string)` | `[]` | no |
 | <a name="input_subnet_mapping"></a> [subnet\_mapping](#input\_subnet\_mapping) | A list of subnet mapping blocks describing subnets to attach to load balancer | `list(map(string))` | `[]` | no |
-| <a name="input_subnets"></a> [subnets](#input\_subnets) | A list of subnet IDs to attach to the LB. Subnets cannot be updated for Load Balancers of type `network`. Changing this value for load balancers of type `network` will force a recreation of the resource | `list(string)` | `[]` | no |
+| <a name="input_subnets"></a> [subnets](#input\_subnets) | A list of subnet IDs to attach to the LB. Subnets cannot be updated for Load Balancers of type `network`. Changing this value for load balancers of type `network` will force a recreation of the resource | `list(string)` | `null` | no |
 | <a name="input_tags"></a> [tags](#input\_tags) | A map of tags to add to all resources | `map(string)` | `{}` | no |
 | <a name="input_target_groups"></a> [target\_groups](#input\_target\_groups) | Map of target group configurations to create | `any` | `{}` | no |
 | <a name="input_timeouts"></a> [timeouts](#input\_timeouts) | Create, update, and delete timeout configurations for the load balancer | `map(string)` | `{}` | no |

variables.tf

@@ -149,7 +149,7 @@ variable "subnet_mapping" {
 variable "subnets" {
   description = "A list of subnet IDs to attach to the LB. Subnets cannot be updated for Load Balancers of type `network`. Changing this value for load balancers of type `network` will force a recreation of the resource"
   type        = list(string)
-  default     = []
+  default     = null
 }
 
 variable "xff_header_processing_mode" {

wrappers/main.tf

@@ -39,7 +39,7 @@ module "wrapper" {
   security_group_use_name_prefix                               = try(each.value.security_group_use_name_prefix, var.defaults.security_group_use_name_prefix, true)
   security_groups                                              = try(each.value.security_groups, var.defaults.security_groups, [])
   subnet_mapping                                               = try(each.value.subnet_mapping, var.defaults.subnet_mapping, [])
-  subnets                                                      = try(each.value.subnets, var.defaults.subnets, [])
+  subnets                                                      = try(each.value.subnets, var.defaults.subnets, null)
   tags                                                         = try(each.value.tags, var.defaults.tags, {})
   target_groups                                                = try(each.value.target_groups, var.defaults.target_groups, {})
   timeouts                                                     = try(each.value.timeouts, var.defaults.timeouts, {})