fix(alb): cannot use null in length due to optional block variables

Output load balancer's dns name and zone id.

Author: saumitra-dev

modules/alb/README.md

@@ -43,9 +43,11 @@ No modules.
 | Name | Description |
 |------|-------------|
 | <a name="output_arn"></a> [arn](#output\_arn) | ARN of the Load Balancer |
+| <a name="output_dns_name"></a> [dns\_name](#output\_dns\_name) | DNS name of the Load Balancer |
 | <a name="output_id"></a> [id](#output\_id) | Identifier of the Load Balancer |
 | <a name="output_listeners_arns"></a> [listeners\_arns](#output\_listeners\_arns) | ARNs of the Listeners |
 | <a name="output_listeners_ids"></a> [listeners\_ids](#output\_listeners\_ids) | Identifiers of the Listeners |
 | <a name="output_target_groups_arns"></a> [target\_groups\_arns](#output\_target\_groups\_arns) | ARNs of the Target Groups |
 | <a name="output_target_groups_ids"></a> [target\_groups\_ids](#output\_target\_groups\_ids) | Identifiers of the Target Groups |
+| <a name="output_zone_id"></a> [zone\_id](#output\_zone\_id) | Canonical hosted zone ID of the Load Balancer (to be used in a Route 53 Alias record) |
 <!-- END_TF_DOCS -->

modules/alb/main.tf

@@ -31,7 +31,7 @@ resource "aws_lb_target_group" "this" {
   target_type = each.value.target_type
 
   dynamic "health_check" {
-    for_each = length(try(each.value.health_check, {})) > 0 ? [1] : []
+    for_each = (try(each.value.health_check, null) != null && length(try(each.value.health_check, {})) > 0) ? [1] : []
 
     content {
       enabled             = try(each.value.health_check.enabled, null)
@@ -65,7 +65,7 @@ resource "aws_lb_listener" "this" {
   ssl_policy      = element(var.listeners, count.index).ssl_policy
 
   dynamic "mutual_authentication" {
-    for_each = length(try(element(var.listeners, count.index).mutual_authentication, {})) > 0 ? [1] : []
+    for_each = (try(element(var.listeners, count.index).mutual_authentication, null) != null && length(try(element(var.listeners, count.index).mutual_authentication, {})) > 0) ? [1] : []
 
     content {
       mode                             = element(var.listeners, count.index).mutual_authentication.mode
@@ -84,7 +84,7 @@ resource "aws_lb_listener" "this" {
       order            = default_action.value.order
 
       dynamic "authenticate_cognito" {
-        for_each = length(try(default_action.value.authenticate_cognito, {})) > 0 ? [1] : []
+        for_each = (try(default_action.value.authenticate_cognito, null) != null && length(try(default_action.value.authenticate_cognito, {})) > 0) ? [1] : []
 
         content {
           user_pool_arn                       = default_action.value.authenticate_cognito.user_pool_arn
@@ -99,7 +99,7 @@ resource "aws_lb_listener" "this" {
       }
 
       dynamic "authenticate_oidc" {
-        for_each = length(try(default_action.value.authenticate_oidc, {})) > 0 ? [1] : []
+        for_each = (try(default_action.value.authenticate_oidc, null) != null && length(try(default_action.value.authenticate_oidc, {})) > 0) ? [1] : []
 
         content {
           authorization_endpoint              = default_action.value.authenticate_oidc.authorization_endpoint
@@ -117,7 +117,7 @@ resource "aws_lb_listener" "this" {
       }
 
       dynamic "fixed_response" {
-        for_each = length(try(default_action.value.fixed_response, {})) > 0 ? [1] : []
+        for_each = (try(default_action.value.fixed_response, null) != null && length(try(default_action.value.fixed_response, {})) > 0) ? [1] : []
 
         content {
           content_type = default_action.value.fixed_response.content_type
@@ -127,7 +127,7 @@ resource "aws_lb_listener" "this" {
       }
 
       dynamic "forward" {
-        for_each = length(try(default_action.value.forward, {})) > 0 ? [1] : []
+        for_each = (try(default_action.value.forward, null) != null && length(try(default_action.value.forward, {})) > 0) ? [1] : []
 
         content {
           dynamic "target_group" {
@@ -141,7 +141,7 @@ resource "aws_lb_listener" "this" {
           }
 
           dynamic "stickiness" {
-            for_each = length(try(default_action.value.forward.stickiness, {})) > 0 ? [1] : []
+            for_each = (try(default_action.value.forward.stickiness, null) != null && length(try(default_action.value.forward.stickiness, {})) > 0) ? [1] : []
 
             content {
               duration = default_action.value.forward.stickiness.duration
@@ -152,7 +152,7 @@ resource "aws_lb_listener" "this" {
       }
 
       dynamic "redirect" {
-        for_each = length(try(default_action.value.redirect, {})) > 0 ? [1] : []
+        for_each = (try(default_action.value.redirect, null) != null && length(try(default_action.value.redirect, {})) > 0) ? [1] : []
 
         content {
           status_code = default_action.value.redirect.status_code

modules/alb/outputs.tf

@@ -12,6 +12,16 @@ output "arn" {
   value       = aws_lb.this.arn
 }
 
+output "dns_name" {
+  description = "DNS name of the Load Balancer"
+  value       = aws_lb.this.dns_name
+}
+
+output "zone_id" {
+  description = "Canonical hosted zone ID of the Load Balancer (to be used in a Route 53 Alias record)"
+  value       = aws_lb.this.zone_id
+}
+
 ################################################################################
 # Load Balancer Target Group
 ################################################################################