yo dawg

1.tpl

example config block {
  foo = bar
  ${tpl2}
}

2.tpl

baz = qux

main.tf

variable "add_tpl2" {
  default = "1"
}

data "template_file" "tpl1" {
  template = "${file("${path.module}/1.tpl")}"

  vars {
    tpl2 = "${var.add_tpl2 ? data.template_file.tpl2.rendered : ""}"
  }
}

data "template_file" "tpl2" {
  template = "${file("${path.module}/2.tpl")}"
}

resource "null_resource" "n" {
  triggers {
    uuid = "${uuid()}"
  }

  provisioner "local-exec" {
    command = "echo \"${data.template_file.tpl1.rendered}\""
  }
}

output.txt

#
# Don't include template 2
#

$ terraform apply
data.template_file.tpl2: Refreshing state...
data.template_file.tpl1: Refreshing state...

Terraform will perform the following actions:

  + null_resource.n
      id:            <computed>
      triggers.%:    "1"
      triggers.uuid: "0bb22aed-2f9b-e939-4cd3-2d04b0e5c252"

null_resource.n: Creating...
null_resource.n (local-exec): Executing: ["/bin/sh" "-c" "echo \"example config block {\n  foo = bar\n  \n}\n\""]
null_resource.n (local-exec): example config block {
null_resource.n (local-exec):   foo = bar

null_resource.n (local-exec): }

null_resource.n: Creation complete after 0s (ID: 9171632323409189307)

Apply complete! Resources: 1 added, 0 changed, 0 destroyed.




#
# Include template 2
#

$ terraform apply
data.template_file.tpl2: Refreshing state...
data.template_file.tpl1: Refreshing state...
null_resource.n: Refreshing state... (ID: 9171632323409189307)

Terraform will perform the following actions:

-/+ null_resource.n (new resource required)
      id:            "9171632323409189307" => <computed> (forces new resource)
      triggers.%:    "1" => "1"
      triggers.uuid: "902927f8-0a25-bcac-43b7-ab19ba741440" => "4568668e-8bf5-b8ca-bb7c-939238c69f52" (forces new resource)


null_resource.n: Creating...
null_resource.n: Provisioning with 'local-exec'...
null_resource.n (local-exec): Executing: ["/bin/sh" "-c" "echo \"example config block {\n  foo = bar\n  baz = qux\n\n}\n\""]
null_resource.n (local-exec): example config block {
null_resource.n (local-exec):   foo = bar
null_resource.n (local-exec):   baz = qux

null_resource.n (local-exec): }

null_resource.n: Creation complete after 0s (ID: 6202997425923817641)

Apply complete! Resources: 1 added, 0 changed, 1 destroyed.