Terraform 13, how to reference the output of a single instance of a module that uses count

Question

I have a module that creates multiple buckets:

module "s3_bucket" {
  source  = "terraform-aws-modules/s3-bucket/aws"
  count   = length(var.buckets)
  bucket  = "bucket-${var.buckets[count.index]}"
}

I'd like to apply a bucket policy to only one of those instances:

resource "aws_s3_bucket_policy" "policy" {
  bucket = module.s3_bucket.THAT_ONE_BUCKET_BY_NAME

  policy = jsonencode(
    {
        "Version": "2012-10-17",
        "Statement": [
            {
                "Effect": "Allow",
                "Principal": {
                    "AWS": [
                        "arn:aws:iam::1111111111:role/access-role"
                    ]
                },
                "Action": [
                    "s3:PutObject"

                ],
                "Resource": [
                    "arn:aws:s3:::THAT_ONE_BUCKET_BY_NAME",
                    "arn:aws:s3:::THAT_ONE_BUCKET_BY_NAME/*"
                ]
            }
        ]
    }
  )

what's the right way to do this in terraform 13?

Answer 1

You have to use index , such as 0, 1, 2, depending on length(var.buckets) . For example,

bucket = module.s3_bucket[0].name

Answer 2

When you use count in this module block, the symbol module.s3_bucket becomes a list of objects rather than just a single object representing one set of outputs.

Therefore in order to access the name of only one of them you'll need to know the index of the one you want to use and access it using the normal index syntax:

module.s3_bucket[0].name

(the above is assuming that your module has an output "name" which returns the bucket name.)