terranix

HCL is the language of terraform. It has its flaws, this is why terranix was born.

declarations

In HCL you would do something like this:

resource "aws_instance" "web" {
  ami           = "${data.aws_ami.ubuntu.id}"
  instance_type = "t2.micro"
  tags = {
    Name = "HelloWorld"
  }
}

Which is the equivalent for the following in terranix:

resource."aws_instance"."web" = {
  ami = "\${data.aws_ami.ubuntu.id}";
  instance_type = "t2.micro";
  tags = {
    Name = "HelloWorld";
  };
}

references

In HCL you can only reference variable outputs. But in terranix, because it is nix, you can basically reference everything.

For example if you have a resource and you want to reuse its parameters:

resource.hcloud_server.myserver = {
  name = "node1";
  image = "debian-9";
  server_type = "cx11";
};

You can reference parameters the terraform way.

resource.hcloud_server.myotherserver = {
  name = "node2";
  image = "\${ hcloud_server.myserver.image }";
  server_type = "\${ hcloud_server.myserver.server_type }";
};

Or the terranix way:

{ config, ... }:
resource.hcloud_server.myotherotherserver = {
  name = "node3";
  image = config.resource.hcloud_server.myserver.image;
  server_type = config.resource.hcloud_server.myserver.server_type;
};

Or the terranix pro way:

{ config, ... }:
resource.hcloud_server.myotherotherotherserver = {
  name = "node4";
  inherit (config.resource.hlcoud_server) image server_type;
};

terranix references being evaluated when generating the json file. terraform references being calculated when running terraform.

multi line strings

In terraform you can create multi line strings using the heredoc style.

variable "multiline" {
  description = <<EOT
Description for the multi line variable.
The indentation here is not wrong.
The terminating word must be on a new line without any indentation.
EOT
}

This won't work in terranix. In terranix you have to use the nix way of multi line strings.

variable.multiline.description = ''
  Description for the multi line variable.
  The indentation here is not wrong.
  All spaces in front of the text block will be removed by terranix.
'';

escaping expressions

The form ${expression} is used by terranix and terraform. So if you want to use a terraform expression in terranix, you have to escape it. Escaping differs for multi and single line strings.

escaping in single line strings

In a single line strings, you escape via \${expression}. For example :

variable.hcloud_token = {};
provider.hcloud.token = "\${ var.hcloud_token }";

You can avoid escaping $ with the tfRef function:

{ lib, ... }:
variable.hcloud_token = {};
provider.hcloud.token = lib.tfRef "var.hcloud_token";

escaping in multi line strings

In multi line strings, you escape via ''${expression}. For example :

resource.local_file.sshConfig = {
  filename = "./ssh-config";
  content = ''
    Host ''${ hcloud_server.terranix_test.ipv4_address }
    IdentityFile ./sshkey
  '';
};