Null values for some arguments cause Terraform errors

[mpaluchowski]

Found a bug? Maybe our Slack Community can help.

Describe the Bug

Terraform is throwing errors for the var.unauthenticated_priority variable being null -- which is its default value. This is probably due to issue 24142 reported in Terraform.

╷
│ Error: Operation failed
│ 
│   on .terraform/modules/ci_alb_ingress/main.tf line 180, in resource "aws_lb_listener_rule" "unauthenticated_hosts":
│  180:   priority     = var.unauthenticated_priority > 0 ? var.unauthenticated_priority + count.index : null
│     ├────────────────
│     │ var.unauthenticated_priority is null
│ 
│ Error during operation: argument must not be null.
╵

Expected Behavior

The default value should be such that no error is thrown.

Steps to Reproduce

Steps to reproduce the behavior:

1. Add a module using terraform-aws-alb-ingress
2. omit passing the unauthenticated_priority parameter.
3. Run terraform apply
4. See error

Environment (please complete the following information):

Anything that will help us triage the bug will help. Here are some ideas:

• OS: Linux Ubuntu 21.04, Terraform 1.0.6
• Version 0.24.0

[januaryjon]

I found a good workaround is to set unauthenticated_priority = -1

Perhaps can fix this bug by making said variable default to -1?

[nitrocode]

The value of unauthenticated_priority now defaults to null.

https://github.com/cloudposse/terraform-aws-alb-ingress#input_unauthenticated_priority

@januaryjon @mpaluchowski is this still an issue ?

[mpaluchowski]

If the default is still null then yes, this is still a problem, because null isn't an allowed value. See my original report.

[nitrocode]

Perhaps we can default it to -1 instead