Fix variable enabled=false results in errors

examples/complete/fixtures.disabled.tfvars

@@ -0,0 +1 @@
+enabled = false

examples/complete/fixtures.enabled.tfvars

@@ -0,0 +1 @@
+enabled = true

examples/complete/main.tf

@@ -19,6 +19,7 @@ module "vpc" {
 module "public_subnets" {
   source = "../../"
 
+  enabled             = var.enabled
   availability_zones  = var.availability_zones
   vpc_id              = module.vpc.vpc_id
   cidr_block          = local.public_cidr_block
@@ -32,6 +33,7 @@ module "public_subnets" {
 module "private_subnets" {
   source = "../../"
 
+  enabled            = var.enabled
   availability_zones = var.availability_zones
   vpc_id             = module.vpc.vpc_id
   cidr_block         = local.private_cidr_block

main.tf

@@ -1,4 +1,5 @@
 locals {
-  public_enabled  = module.this.enabled && var.type == "public"
-  private_enabled = module.this.enabled && var.type == "private"
+  public_enabled     = module.this.enabled && var.type == "public"
+  private_enabled    = module.this.enabled && var.type == "private"
+  availability_zones = (module.this.enabled) ? var.availability_zones : []
 }

outputs.tf

@@ -1,32 +1,32 @@
 output "az_subnet_ids" {
-  value = zipmap(
-    var.availability_zones,
-    coalescelist(aws_subnet.private.*.id, aws_subnet.public.*.id),
-  )
+  # No ellipsis needed since this module makes either public or private subnets. See the TF 0.15 one function
+  value = {
+    for subnet_tuple in concat(local.public_az_subnets, local.private_az_subnets) : subnet_tuple.availability_zone => subnet_tuple.subnet_id
+  }
   description = "Map of AZ names to subnet IDs"
 }
 
 output "az_route_table_ids" {
-  value = zipmap(
-    var.availability_zones,
-    coalescelist(aws_route_table.private.*.id, aws_route_table.public.*.id),
-  )
+  # No ellipsis needed since this module makes either public or private subnets. See the TF 0.15 one function
+  value = {
+    for route_table_tuple in concat(local.public_az_route_table_ids, local.private_az_route_table_ids) : route_table_tuple.availability_zone => route_table_tuple.route_table_id
+  }
   description = " Map of AZ names to Route Table IDs"
 }
 
 output "az_ngw_ids" {
-  value = zipmap(
-    var.availability_zones,
-    coalescelist(aws_nat_gateway.public.*.id, local.dummy_az_ngw_ids),
-  )
+  # No ellipsis needed since this module makes either public or private subnets. See the TF 0.15 one function
+  value = {
+    for nat_gw_tuple in concat(local.public_az_ngw_ids, local.private_az_ngw_ids) : nat_gw_tuple.availability_zone => nat_gw_tuple.nat_gateway_id
+  }
   description = "Map of AZ names to NAT Gateway IDs (only for public subnets)"
 }
 
 output "az_subnet_arns" {
-  value = zipmap(
-    var.availability_zones,
-    coalescelist(aws_subnet.private.*.arn, aws_subnet.public.*.arn),
-  )
+  # No ellipsis needed since this module makes either public or private subnets. See the TF 0.15 one function
+  value = {
+    for subnet_tuple in concat(local.public_az_subnets, local.private_az_subnets) : subnet_tuple.availability_zone => subnet_tuple.subnet_arn
+  }
   description = "Map of AZ names to subnet ARNs"
 }
 

private.tf

@@ -16,14 +16,14 @@ resource "aws_subnet" "private" {
   count = local.private_count
 
   vpc_id            = var.vpc_id
-  availability_zone = var.availability_zones[count.index]
+  availability_zone = local.availability_zones[count.index]
   cidr_block        = cidrsubnet(var.cidr_block, ceil(log(var.max_subnets, 2)), count.index)
 
   tags = merge(
     module.private_label.tags,
     {
       "Name" = "${module.private_label.id}${module.this.delimiter}${element(var.availability_zones, count.index)}"
-      "AZ"   = var.availability_zones[count.index]
+      "AZ"   = local.availability_zones[count.index]
       "Type" = var.type
     },
   )
@@ -75,7 +75,7 @@ resource "aws_route_table" "private" {
     module.private_label.tags,
     {
       "Name" = "${module.private_label.id}${module.this.delimiter}${element(var.availability_zones, count.index)}"
-      "AZ"   = element(var.availability_zones, count.index)
+      "AZ"   = element(local.availability_zones, count.index)
       "Type" = var.type
     },
   )
@@ -96,14 +96,30 @@ resource "aws_route" "default" {
   count = local.private_route_count
 
   route_table_id = zipmap(
-    var.availability_zones,
+    local.availability_zones,
     matchkeys(
       aws_route_table.private.*.id,
       aws_route_table.private.*.tags.AZ,
-      var.availability_zones,
+      local.availability_zones,
     ),
   )[element(keys(var.az_ngw_ids), count.index)]
   nat_gateway_id         = var.az_ngw_ids[element(keys(var.az_ngw_ids), count.index)]
   destination_cidr_block = "0.0.0.0/0"
   depends_on             = [aws_route_table.private]
 }
+
+locals {
+  private_az_subnets = tolist([for subnet in aws_subnet.private[*] : {
+    availability_zone = subnet.tags.AZ
+    subnet            = subnet
+    subnet_id         = subnet.id
+    subnet_arn        = subnet.arn
+  }])
+  private_az_route_table_ids = tolist([for route_table in aws_route_table.private[*] : {
+    availability_zone = route_table.tags.AZ
+    route_table       = route_table
+    route_table_id    = route_table.id
+  }])
+  # NAT gateways not present in private subnets
+  private_az_ngw_ids = tolist([])
+}

public.tf

@@ -1,6 +1,6 @@
 locals {
-  public_count              = local.public_enabled ? length(var.availability_zones) : 0
-  public_nat_gateways_count = local.public_enabled && var.nat_gateway_enabled ? length(var.availability_zones) : 0
+  public_count              = local.public_enabled ? length(local.availability_zones) : 0
+  public_nat_gateways_count = local.public_enabled && var.nat_gateway_enabled ? length(local.availability_zones) : 0
 }
 
 module "public_label" {
@@ -16,14 +16,14 @@ resource "aws_subnet" "public" {
   count = local.public_count
 
   vpc_id            = var.vpc_id
-  availability_zone = element(var.availability_zones, count.index)
+  availability_zone = element(local.availability_zones, count.index)
   cidr_block        = cidrsubnet(var.cidr_block, ceil(log(var.max_subnets, 2)), count.index)
 
   tags = merge(
     module.public_label.tags,
     {
       "Name" = "${module.public_label.id}${module.this.delimiter}${element(var.availability_zones, count.index)}"
-      "AZ"   = element(var.availability_zones, count.index)
+      "AZ"   = element(local.availability_zones, count.index)
       "Type" = var.type
     },
   )
@@ -74,7 +74,7 @@ resource "aws_route_table" "public" {
     module.public_label.tags,
     {
       "Name" = "${module.public_label.id}${module.this.delimiter}${element(var.availability_zones, count.index)}"
-      "AZ"   = element(var.availability_zones, count.index)
+      "AZ"   = element(local.availability_zones, count.index)
       "Type" = var.type
     },
   )
@@ -121,38 +121,27 @@ resource "aws_nat_gateway" "public" {
     module.public_label.tags,
     {
       "Name" = "${module.public_label.id}${module.this.delimiter}${element(var.availability_zones, count.index)}"
-      "AZ"   = element(var.availability_zones, count.index)
+      "AZ"   = element(local.availability_zones, count.index)
       "Type" = var.type
     },
   )
 }
 
-# Dummy list of NAT Gateway IDs to use in the outputs for private subnets and when `nat_gateway_enabled=false` for public subnets
-# Needed due to Terraform limitation of not allowing using conditionals with maps and lists
 locals {
-  dummy_az_ngw_ids = slice(
-    [
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-      "0",
-    ],
-    0,
-    length(var.availability_zones),
-  )
+  public_az_subnets = tolist([for subnet in aws_subnet.public[*] : {
+    availability_zone = subnet.tags.AZ
+    subnet            = subnet
+    subnet_id         = subnet.id
+    subnet_arn        = subnet.arn
+  }])
+  public_az_route_table_ids = tolist([for route_table in aws_route_table.public[*] : {
+    availability_zone = route_table.tags.AZ
+    route_table       = route_table
+    route_table_id    = route_table.id
+  }])
+  public_az_ngw_ids = tolist([for nat_gateway in aws_nat_gateway.public[*] : {
+    availability_zone = nat_gateway.tags.AZ
+    nat_gateway_id    = nat_gateway.id
+  }])
 }
 

test/src/examples_complete_test.go

@@ -24,7 +24,8 @@ func assertValueStartsWith(t *testing.T, m map[string]string, rx interface{}) {
 
 // Test the Terraform module in examples/complete using Terratest.
 func TestExamplesComplete(t *testing.T) {
-	t.Parallel()
+	// Init phase module download fails when run in parallel
+	//t.Parallel()
 
 	terraformOptions := &terraform.Options{
 		// The path to where our Terraform code is located
@@ -40,35 +41,35 @@ func TestExamplesComplete(t *testing.T) {
 	// This will run `terraform init` and `terraform apply` and fail the test if there are any errors
 	terraform.InitAndApply(t, terraformOptions)
 
-/*
-   Outputs:
-
-   private_az_route_table_ids = {
-     "us-east-2a" = "rtb-0489137a5c668e49b"
-     "us-east-2b" = "rtb-083c0e942abb4b8a1"
-     "us-east-2c" = "rtb-0c36484693db5e774"
-   }
-   private_az_subnet_ids = {
-     "us-east-2a" = "subnet-0f56deccfe81c0ea0"
-     "us-east-2b" = "subnet-05861d30d45e7b675"
-     "us-east-2c" = "subnet-036d747a2b46857ae"
-   }
-   public_az_ngw_ids = {
-     "us-east-2a" = "nat-0f5057f09b8cd8ddc"
-     "us-east-2b" = "nat-0971b2505ea6d03f1"
-     "us-east-2c" = "nat-0dc1cdf91010be057"
-   }
-   public_az_route_table_ids = {
-     "us-east-2a" = "rtb-0642afb4401f1eef1"
-     "us-east-2b" = "rtb-04f511a28a2d5a6a2"
-     "us-east-2c" = "rtb-05f0ee4e831b05697"
-   }
-   public_az_subnet_ids = {
-     "us-east-2a" = "subnet-0dcb9e32f1f02a367"
-     "us-east-2b" = "subnet-0b432a6748ca40638"
-     "us-east-2c" = "subnet-00a9a6636ca722474"
-   }
- */
+	/*
+	   Outputs:
+
+	   private_az_route_table_ids = {
+	     "us-east-2a" = "rtb-0489137a5c668e49b"
+	     "us-east-2b" = "rtb-083c0e942abb4b8a1"
+	     "us-east-2c" = "rtb-0c36484693db5e774"
+	   }
+	   private_az_subnet_ids = {
+	     "us-east-2a" = "subnet-0f56deccfe81c0ea0"
+	     "us-east-2b" = "subnet-05861d30d45e7b675"
+	     "us-east-2c" = "subnet-036d747a2b46857ae"
+	   }
+	   public_az_ngw_ids = {
+	     "us-east-2a" = "nat-0f5057f09b8cd8ddc"
+	     "us-east-2b" = "nat-0971b2505ea6d03f1"
+	     "us-east-2c" = "nat-0dc1cdf91010be057"
+	   }
+	   public_az_route_table_ids = {
+	     "us-east-2a" = "rtb-0642afb4401f1eef1"
+	     "us-east-2b" = "rtb-04f511a28a2d5a6a2"
+	     "us-east-2c" = "rtb-05f0ee4e831b05697"
+	   }
+	   public_az_subnet_ids = {
+	     "us-east-2a" = "subnet-0dcb9e32f1f02a367"
+	     "us-east-2b" = "subnet-0b432a6748ca40638"
+	     "us-east-2c" = "subnet-00a9a6636ca722474"
+	   }
+	*/
 
 	// Run `terraform output` to get the value of an output variable
 	privateSubnetIds := terraform.OutputMap(t, terraformOptions, "private_az_subnet_ids")
@@ -94,3 +95,36 @@ func TestExamplesComplete(t *testing.T) {
 	assert.Equal(t, expectedAZs, getKeys(publicSubnetIds))
 	assertValueStartsWith(t, publicSubnetIds, "^subnet-.*")
 }
+
+func TestExamplesCompleteDisabledModule(t *testing.T) {
+	// Init phase module download fails when run in parallel
+	//t.Parallel()
+
+	terraformOptions := &terraform.Options{
+		// The path to where our Terraform code is located
+		TerraformDir: "../../examples/complete",
+		Upgrade:      true,
+		// Variables to pass to our Terraform code using -var-file options
+		VarFiles: []string{"fixtures.us-east-2.tfvars", "fixtures.disabled.tfvars"},
+	}
+
+	// At the end of the test, run `terraform destroy` to clean up any resources that were created
+	defer terraform.Destroy(t, terraformOptions)
+
+	// This will run `terraform init` and `terraform apply` and fail the test if there are any errors
+	terraform.InitAndApply(t, terraformOptions)
+
+	privateNATGateWayIds := terraform.OutputMap(t, terraformOptions, "private_az_ngw_ids")
+	privateSubnetIds := terraform.OutputMap(t, terraformOptions, "private_az_subnet_ids")
+	privateRouteTableIds := terraform.OutputMap(t, terraformOptions, "private_az_route_table_ids")
+	publicNATGateWayIds := terraform.OutputMap(t, terraformOptions, "public_az_ngw_ids")
+	publicRouteTableIds := terraform.OutputMap(t, terraformOptions, "public_az_route_table_ids")
+	publicSubnetIds := terraform.OutputMap(t, terraformOptions, "public_az_subnet_ids")
+
+	assert.Empty(t, privateNATGateWayIds)
+	assert.Empty(t, privateSubnetIds)
+	assert.Empty(t, privateRouteTableIds)
+	assert.Empty(t, publicNATGateWayIds)
+	assert.Empty(t, publicSubnetIds)
+	assert.Empty(t, publicRouteTableIds)
+}