Label order

[Jamie-BitFlight]

A new variable that allows for providing a label_order as a list to specify which variables and in what order they go into the id output and Name tag.

The list can include all or none of the a variable names:
"namespace", "environment", "stage", "name", "attributes"

Resolves #35

Usage:

module "label1" {
  source      = "../../"
  namespace   = "CloudPosse"
  environment = "UAT"
  stage       = "build"
  name        = "Winston Churchroom"
  attributes  = ["fire", "water", "earth", "air"]

  label_order = ["name", "environment", "stage"]

  tags = {
    "City"        = "Dublin"
    "Environment" = "Private"
  }
}
output "label1" {
  value = {
    id         = "${module.label1.id}"
    name       = "${module.label1.name}"
    namespace  = "${module.label1.namespace}"
    stage      = "${module.label1.stage}"
    attributes = "${module.label1.attributes}"
  }
}

Outputs:

label1 = {
  attributes = fire-water-earth-air
  id = winstonchurchroom-uat-build
  name = winstonchurchroom
  namespace = cloudposse
  stage = build
}

[huksley]

Yes, it works as needed with following setup:

module "label1" {
  source      = "github.com/cloudposse/terraform-null-label?ref=label-order"
  namespace   = "test"
  environment = ""
  stage       = "dev"
  name        = "fe"
  label_order = [ "namespace", "name", "stage"]
}

output "label1" {
  value = {
    id         = "${module.label1.id}"
  }
}

Produces on apply:

Outputs:

label1 = {
  id = test-fe-dev
}

However, I am not using it as is. I am using label through following projects:

https://github.com/cloudposse/terraform-aws-cicd
https://github.com/cloudposse/terraform-aws-codebuild

[aknysh]

I tried to use this simpler and more scalable pattern to generate id (which @osterman suggested):

id = "${join(local.delimiter, distinct(compact(null_resource.id.*.triggers.value)))}"

resource "null_resource" "id" {
  count = "${local.enabled ? length(local.label_order_list) : 0}"

  triggers {
    value = "${local.id_context[local.label_order_list[count.index]]}"
  }
}

It worked OK when
data "null_data_source" "tags_as_list_of_maps"
and
tags_as_list_of_maps = ["${data.null_data_source.tags_as_list_of_maps.*.outputs}"]
were commented out.

After uncommenting it, started to throw errors: null_data_source.tags_as_list_of_maps: value of count can't be computed.

And that’s because we introduced a resource (even if it’s null) and other resources depend on it.
So it looks like TF has issues with counts not only for real resources on AWS, but any resource types (even virtual like null), and even inside one module.

So I ended up using this pattern from @Jamie-BitFlight (simplified a little bit):

id_context = {
    name        = "${local.name}"
    namespace   = "${local.namespace}"
    environment = "${local.environment}"
    stage       = "${local.stage}"
    attributes  = "${local.attributes}"
  }

  id = "${lower(join(local.delimiter, compact(list(
    "${local.label_order_length > 0 ? local.id_context[element(local.label_order_final_list, 0)] : ""}",
    "${local.label_order_length > 1 ? local.id_context[element(local.label_order_final_list, 1)] : ""}",
    "${local.label_order_length > 2 ? local.id_context[element(local.label_order_final_list, 2)] : ""}",
    "${local.label_order_length > 3 ? local.id_context[element(local.label_order_final_list, 3)] : ""}",
    "${local.label_order_length > 4 ? local.id_context[element(local.label_order_final_list, 4)] : ""}"))))}"

Works OK for all scenarios including context and label_order.