Concat 2 lists within AWS IAM role policy statement

Terraform
3

Hi @apparentlymart this works great in my testing here, thanks very much.

However, (And I think this is a tangent here), I’m not sure how I can make this conditional because when I leave the list empty, I end up with an empty policy. Any idea how I can get around this?
If I use:

locals {
  lambda_secrets_access = {
    "dev" = [""]
}

I get:

Terraform will perform the following actions:

  # aws_iam_role_policy.iam_policy_for_lambda_secrets will be updated in-place
  ~ resource "aws_iam_role_policy" "iam_policy_for_lambda_secrets" {
        id     = "policy_id:policy_id"
        name   = "policy_name"
      ~ policy = jsonencode(
          ~ {
              ~ Statement = [
                  ~ {
                        Action   = "secretsmanager:GetSecretValue"
                        Effect   = "Allow"
                      ~ Resource = [
                          - "arn:aws:secretsmanager:eu-west-1:111111111111:secret:my-secret-i-want-access-JHKku8",
                          + "arn:aws:secretsmanager:eu-west-1:111111111111:secret:",
                        ]
                    },
                ]
                Version   = "2012-10-17"
            }
        )
        role   = "role_name"
    }

Plan: 0 to add, 1 to change, 0 to destroy.

Do you want to perform these actions in workspace "dev"?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value:

I tried adding a count statement on the resource:

count = local.lambda_secrets_access[local.environment] != "" ? 1 : 0

But this does not seem to help, the resource still is created incomplete, rather than not at all.

I googled and I’m not sure how conditional resources are implemented into Terraform.
It seems that this isnt a feature at all, and count is used by some to get around it.