Terraform Naming Conventions

This rule applies to files matching the patterns above.

# Terraform Naming Conventions

## Rule
All Terraform resources, variables, outputs, and files MUST follow consistent naming conventions using snake_case for HCL identifiers and kebab-case for cloud resource names.

## HCL Naming (snake_case)
```hcl
# Resources: type + descriptive name
resource "aws_instance" "web_server" {}      # Good
resource "aws_instance" "WebServer" {}       # Bad — PascalCase
resource "aws_instance" "web-server" {}      # Bad — kebab-case

# Variables: descriptive snake_case
variable "vpc_cidr_block" {}                 # Good
variable "vpcCidrBlock" {}                   # Bad — camelCase

# Outputs: descriptive snake_case
output "database_endpoint" {}                # Good
output "db-endpoint" {}                      # Bad — kebab-case

# Locals: snake_case
locals {
  common_tags = {}                           # Good
}
```

## Cloud Resource Naming
```hcl
# Pattern: {project}-{environment}-{resource}-{qualifier}
locals {
  name_prefix = "${var.project}-${var.environment}"
}

resource "aws_vpc" "main" {
  tags = { Name = "${local.name_prefix}-vpc" }
}

resource "aws_subnet" "private" {
  for_each = var.private_subnets
  tags = { Name = "${local.name_prefix}-private-${each.key}" }
}

# Results: myapp-production-vpc, myapp-production-private-us-east-1a
```

## File Organization
```
module/
├── main.tf           # Primary resources
├── variables.tf      # All input variables
├── outputs.tf        # All outputs
├── versions.tf       # Provider and Terraform version constraints
├── locals.tf         # Local values (optional)
├── data.tf           # Data sources (optional)
└── README.md         # Module documentation
```

## Good Examples
```hcl
# Resource naming
resource "aws_security_group" "web_alb" {}
resource "aws_iam_role" "lambda_execution" {}
resource "aws_s3_bucket" "application_logs" {}

# Variable naming
variable "database_instance_class" {
  type        = string
  description = "RDS instance class for the application database"
}

# Output naming
output "load_balancer_dns_name" {
  description = "DNS name of the application load balancer"
}
```

## Bad Examples
```hcl
# Bad: meaningless names
resource "aws_instance" "this" {}
resource "aws_instance" "main" {}  # OK for singleton, bad if multiple

# Bad: abbreviations without context
variable "db_ic" {}  # What is "ic"?

# Bad: inconsistent casing
variable "VPC_CIDR" {}
output "DatabaseEndpoint" {}
```

## Enforcement
- Use tflint with naming convention rules
- CI pipeline validation with `terraform fmt -check`
- Team code review checklist includes naming verification