fix Cloud NAT module internal router name lookup

CHANGELOG.md

@@ -5,6 +5,7 @@ All notable changes to this project will be documented in this file.
 ## [Unreleased]
 
 - fix DNS module internal zone lookup
+- fix Cloud NAT module internal router name lookup
 
 ## [1.3.0] - 2020-04-08
 

modules/net-cloudnat/main.tf

@@ -16,13 +16,15 @@
 
 locals {
   router_name = (
-    var.router_create ? google_compute_router.router[0].name : var.router_name
+    var.router_create
+    ? try(google_compute_router.router[0].name, null)
+    : var.router_name
   )
 }
 
 resource "google_compute_router" "router" {
   count   = var.router_create ? 1 : 0
-  name    = var.router_name == "" ? "${var.name}-nat" : var.router_name
+  name    = var.router_name == null ? "${var.name}-nat" : var.router_name
   project = var.project_id
   region  = var.region
   network = var.router_network

modules/net-cloudnat/outputs.tf

@@ -31,7 +31,11 @@ output "region" {
 
 output "router" {
   description = "Cloud NAT router resources (if auto created)."
-  value       = var.router_create ? google_compute_router.router[0] : null
+  value = (
+    var.router_create
+    ? try(google_compute_router.router[0], null)
+    : null
+  )
 }
 
 output "router_name" {

modules/net-cloudnat/variables.tf

@@ -78,13 +78,13 @@ variable "router_create" {
 variable "router_name" {
   description = "Router name, leave blank if router will be created to use auto generated name."
   type        = string
-  default     = ""
+  default     = null
 }
 
 variable "router_network" {
   description = "Name of the VPC used for auto-created router."
   type        = string
-  default     = ""
+  default     = null
 }
 
 variable "subnetworks" {