Add hack for module depend on

hashicorp/terraform#1178 (comment)

main.tf

@@ -1,3 +1,18 @@
+provider "aws" {}
+
+# Part of a hack for module-to-module dependencies.
+# https://github.com/hashicorp/terraform/issues/1178#issuecomment-449158607
+# and
+# https://github.com/hashicorp/terraform/issues/1178#issuecomment-473091030
+# Make sure to add this null_resource.dependency_getter to the `depends_on`
+# attribute to all resource(s) that will be constructed first within this
+# module:
+resource "null_resource" "dependency_getter" {
+  triggers {
+    my_dependencies = "${join(",", var.dependencies)}"
+  }
+}
+
 resource "aws_security_group" "bastion" {
   count       = "${var.enabled}"
   name        = "${var.name}"
@@ -145,3 +160,19 @@ resource "aws_autoscaling_group" "bastion" {
     create_before_destroy = true
   }
 }
+
+# Part of a hack for module-to-module dependencies.
+# https://github.com/hashicorp/terraform/issues/1178#issuecomment-449158607
+resource "null_resource" "dependency_setter" {
+  # Part of a hack for module-to-module dependencies.
+  # https://github.com/hashicorp/terraform/issues/1178#issuecomment-449158607
+  # List resource(s) that will be constructed last within the module.
+  depends_on = [
+    "aws_security_group.bastion",
+    "aws_security_group_rule.ssh_ingress",
+    "aws_security_group_rule.ssh_sg_ingress",
+    "aws_security_group_rule.bastion_all_egress",
+    "aws_launch_configuration.bastion",
+    "aws_autoscaling_group.bastion",
+  ]
+}

outputs.tf

@@ -9,3 +9,11 @@ output "security_group_id" {
 output "asg_id" {
   value = "${element(concat(aws_autoscaling_group.bastion.*.id, list("")), 0)}"
 }
+
+# Part of a hack for module-to-module dependencies.
+# https://github.com/hashicorp/terraform/issues/1178#issuecomment-449158607
+# and
+# https://github.com/hashicorp/terraform/issues/1178#issuecomment-473091030
+output "depended_on" {
+  value = "${null_resource.dependency_setter.id}-${timestamp()}"
+}

variables.tf

@@ -114,3 +114,7 @@ variable "enabled" {
   default     = true
   description = "Whether to create bastion or not."
 }
+
+variable "dependencies" {
+  type = "list"
+}