Allow multiple instance expansion syntax when instance count is 1

[gaffneyc]

Using the example config below setting up an ELB in front of a set of servers (in this case just 1). Trying to use the splat or expanded syntax (e.g. ${aws_instance.web.*.id}) when count is 1 fails with an error but works fine if count >= 2.

The use case is to have a staging environment with just a single server and scaling that up in production. If we want to have just one instance we need to change the syntax we use depending on the environment or count.

Terraform should allow using the same syntax regardless of what the count it.

resource "aws_elb" "balancer" {
  name = "balancer"

  listener {
    lb_port = 80
    instance_port = 80

    lb_protocol = "http"
    instance_protocol = "http"
  }

  instances = ["${aws_instance.web.*.id}"]
}

resource "aws_instance" "web" {
  ami = "ami-b227efda"
  instance_type = "t2.micro"
  count = 1
}

Running terraform plan errors with:
Error running plan: Resource 'aws_instance.web' does not have attribute 'id' for variable 'aws_instance.web.*.id'

[pearkes]

Could you just specify count = 1 in your staging env? That should work, let me know if it doesn't.

One issue with treating everything as having multiple resources is you get situations like this (which are equally unintuitive):

${route_53_record.apex.0.value}

There's only ever one apex record, so indexing it feels cumbersome.

Let me know if that works for you!

[pearkes]

Ah, sorry, misread part of your issue, count=1 should indeed work, re-opening and tagged as a bug.

[mitchellh]

Fixed! Thanks.

[gaffneyc]

Thanks! 🤘