TERRAFORM_STYLE_GUIDE.md

Terraform Style Guide

Table of Contents

• Introduction
• General
  • Resource Block Alignment
  • String Values
  • Spacing
  • Comments
  • Organizing Block labels, Variables and Outputs
• Naming Conventions
  • File Names
  • Parameter, Meta-parameter and Variable Naming
  • Resource Naming

Introduction

This document provides coding conventions used in all Solid Potential repositories for Terraform's HashiCorp Configuration Language (HCL). Code convetion are introduced to adhere a style guide to ensure readable and high quality code.

General

Resource Block Alignment

Parameter definitions in a resource block should be aligned. The terraform fmt command can do this for you.

String Values

• Strings are in double-quotes.

Spacing

Use 2 spaces when defining resources except when defining inline policies or other inline resources.

Comments

When commenting use a hash # and a space in front of the comment. We prefer # over // or /**/ for line comments. For delimiting section header comment blocks with # ----- <SECTION_NAME> -----.

Organizing Block labels, Variables and Outputs

The label for blocks should be in snake case and lowercase. i.e.: example_instance , not ExampleInstance or example-instance

Variables and outputs should be created based on following rules:

• Name - similarly to blocks both variables and outputs should be in snake case and lowercase. Additinally:
  • Names should reflect the attribute or argument they reference in its suffix i.e.: foo_bar_name or foo_bar_id but not foo_bar
  • Use plural form in names of variables that expect a collection of items i.e.: foo_bars for multiple items or foo_bar for single item
• Description - each variable or output shoul contain meaningful description
• Type - each variable or output should contain defined type even if it is of type string (default)
• Defaults (Optional) - if a module should configure anything using miminal configuration use defaults in variables rather than hardcode values used in resources

The variables.tf file should be broken down into three sections with each section arranged alphabetically. Starting at the top of the file:

1. Variables that have no defaults defined
2. Variables that contain defaults
3. All locals blocks

Conditionals

Use () to break up complex conditionals across multiple lines for better readability. i.e.:

locals {
  is_prod = var.environment == "prod" ? true : false

  instance_name = (
    var.instance_name != "" 
    ? var.instance_name 
    : "vm-${var.image_name}"
  )
}

Naming Conventions

File Names

Create a separate resource file for each type resource. Similar or bundled resources should be defined in the same file and named accordingly.

Parameter, Meta-parameter and Variable Naming

Only use an underscore (_) when naming Terraform resources like TYPE/NAME parameters and variables.

resource "google_compute_instance" "vm_instance" {
    ...
}

Resource Naming

Only use a hyphen (-) when naming the component being created.

resource "google_compute_instance" "vm_instance" {
  name = "test-vm"  
  ...
}

A resource's NAME should be the same as the TYPE minus the provider.

  resource "google_storage_bucket" "storage_bucket" {
    ...
  }

If there are multiple resources of the same TYPE defined, add a minimalistic identifier to differentiate between the two resources. A blank line should sperate resource definitions contained in the same file.

# Create Data Bucket
  resource "google_storage_bucket" "data_storage_bucket" {
    ...
  }

# Create Images Bucket
  resource "google_storage_bucket" "images_storage_bucket" {
    ...
  }