Crearting lambda as target group causes aws_lb_target_group issue on first apply

[scott-doyland-burrows]

Versions

• Module version [Required]:9.12.0

• Terraform version:
  Terraform v1.10.0
  on linux_amd64

• provider registry.terraform.io/hashicorp/aws v5.81.0
• provider registry.terraform.io/hashicorp/external v2.3.4
• provider registry.terraform.io/hashicorp/local v2.5.2
• provider registry.terraform.io/hashicorp/null v3.2.3

Reproduction Code [Required]

module "alb" {
  source  = "terraform-aws-modules/alb/aws"
  version = "9.12.0"

  providers = {
    aws = aws.account
  }

  name    = local.name
  vpc_id  = module.vpc.vpc_id
  subnets = module.vpc.public_subnets

  target_groups = {
    session_manager_main = {
      name                     = "session-manager-main"
      target_type              = "lambda"
      target_id                = module.lambda.lambda_function_arn
      attach_lambda_permission = true
      port                     = null
    }
  }
}

Steps to reproduce the behavior:

terraform apply - warning on first run

Expected behavior

should apply without warning.

Actual behavior

│ Warning: Invalid Attribute Combination
│
│   with module.alb.aws_lb_target_group.this["session_manager_main"],
│   on .terraform/modules/alb/main.tf line 518, in resource "aws_lb_target_group" "this":
│  518:   port                               = try(each.value.target_type, null) == "lambda" ? null : try(each.value.port, var.default_port)
│
│ Attribute "port" cannot be specified when "target_type" is "lambda".
│
│ This will be an error in a future release.

Additional context

A second (and any future) apply ran without errors. It is only the first apply that produces the error.

Looks like the use of port = null has maybe been deprecated completely when using lambda as a target group.

hashicorp/terraform-provider-aws#35457