use a new 'create_router' variable to trigger router creation

main.tf

@@ -28,12 +28,12 @@ locals {
   # locals for google_compute_router_nat
   nat_ip_allocate_option = var.nat_ip_allocate_option ? var.nat_ip_allocate_option : local.default_nat_ip_allocate_option
   name                   = var.name != "" ? var.name : local.default_name
-  router                 = var.router == "" ? google_compute_router.router[0].name : var.router
+  router                 = var.create_router ? google_compute_router.router[0].name : var.router
 }
 
 resource "google_compute_router" "router" {
-  count   = var.router == "" ? 1 : 0
-  name    = "${local.name}-router"
+  count   = var.create_router ? 1 : 0
+  name    = var.router
   project = var.project_id
   region  = var.region
   network = var.network

outputs.tf

@@ -31,6 +31,6 @@ output "region" {
 
 output "router_name" {
   description = "Cloud NAT router name"
-  value       = var.router
+  value       = local.router
 }
 

variables.tf

@@ -53,9 +53,13 @@ variable "network" {
   default     = ""
 }
 
+variable "create_router" {
+  description = "Create router instead of using an existing one, uses 'router' variable for new resource name."
+  default     = false
+}
+
 variable "router" {
   description = "The name of the router in which this NAT will be configured. Changing this forces a new NAT to be created."
-  default     = ""
 }
 
 variable "router_asn" {