Fixes for BYO VPC:

* don't condition the creation of the VPC resource
  (hashicorp/hil#50)
* pass external subnet IDs into the VPC module

modules/aws/vpc/variables.tf

@@ -15,9 +15,14 @@ variable "external_vpc_id" {
 }
 
 variable "external_master_subnets" {
-  type    = "list"
+  type = "list"
 }
 
 variable "external_worker_subnets" {
-  type    = "list"
+  type = "list"
+}
+
+variable "dummy_vpc_name" {
+  type    = "string"
+  default = "terraform-side-effect"
 }

modules/aws/vpc/vpc-public.tf

@@ -14,6 +14,7 @@ resource "aws_route_table" "default" {
 }
 
 resource "aws_main_route_table_association" "main_vpc_routes" {
+  count          = "${var.external_vpc_id == "" ? 1 : 0}"
   vpc_id         = "${data.aws_vpc.cluster_vpc.id}"
   route_table_id = "${aws_route_table.default.id}"
 }

modules/aws/vpc/vpc.tf

@@ -1,13 +1,20 @@
 data "aws_availability_zones" "azs" {}
 
 resource "aws_vpc" "new_vpc" {
-  count                = "${length(var.external_vpc_id) > 0 ? 0 : 1}"
-  cidr_block           = "${var.cidr_block}"
+  # count                = "${length(var.external_vpc_id) > 0 ? 0 : 1}"
+  #
+  # We can't yet use the count gate here because of terraform issues:
+  # https://github.com/hashicorp/hil/issues/50
+  # https://github.com/hashicorp/terraform/issues/11566
+  # This should be re-enabled when above issues are fixed.
+  #
+  cidr_block = "${var.cidr_block}"
+
   enable_dns_hostnames = true
   enable_dns_support   = true
 
   tags {
-    Name              = "${var.cluster_name}"
+    Name              = "${var.external_vpc_id == "" ? var.cluster_name : "${var.cluster_name}-${var.dummy_vpc_name}"}"
     KubernetesCluster = "${var.cluster_name}"
   }
 }

platforms/aws/main.tf

@@ -1,15 +1,15 @@
 data "aws_availability_zones" "azs" {}
 
 module "vpc" {
-  source                       = "../../modules/aws/vpc"
+  source = "../../modules/aws/vpc"
 
   az_count     = "${var.tectonic_aws_az_count}"
   cidr_block   = "${var.tectonic_aws_vpc_cidr_block}"
   cluster_name = "${var.tectonic_cluster_name}"
 
   external_vpc_id         = "${var.tectonic_aws_external_vpc_id}"
-  external_master_subnets = []
-  external_worker_subnets = []
+  external_master_subnets = ["${compact(var.tectonic_aws_external_master_subnets)}"]
+  external_worker_subnets = ["${compact(var.tectonic_aws_external_worker_subnets)}"]
 }
 
 module "etcd" {
@@ -89,4 +89,4 @@ module "workers" {
   ssh_key    = "${var.tectonic_aws_ssh_key}"
   cl_channel = "${var.tectonic_cl_channel}"
   user_data  = "${module.ignition-workers.ignition}"
-}
+}

platforms/aws/variables.tf

@@ -24,4 +24,14 @@ variable "tectonic_aws_az_count" {
 
 variable "tectonic_aws_external_vpc_id" {
   type = "string"
-}
+}
+
+variable "tectonic_aws_external_master_subnets" {
+  type    = "list"
+  default = [""]
+}
+
+variable "tectonic_aws_external_worker_subnets" {
+  type    = "list"
+  default = [""]
+}