Validate HCL Block Structure

Structural HCL Validation

Before running terraform validate (which requires provider plugins and initialization), you can catch many common errors with structural validation. The formatter checks for balanced delimiters and proper nesting.

Common Structural Errors

Unclosed brace:

resource "aws_instance" "web" {
  ami           = "ami-12345678"
  instance_type = "t3.micro"

  tags = {
    Name = "web"
  # Missing closing brace for tags
}

Mismatched brackets:

variable "allowed_cidrs" {
  type    = list(string)
  default = [
    "10.0.0.0/8",
    "172.16.0.0/12",
  # Missing closing bracket
}

Unclosed parenthesis:

locals {
  subnet = cidrsubnet(var.vpc_cidr, 8, 0
}

What the Validator Checks

Check	Description
Matched {}	Every opening brace has a closing brace
Matched []	Every opening bracket has a closing bracket
Matched ()	Every opening parenthesis has a closing parenthesis
Nesting order	Closing delimiters match the most recent opening delimiter
String boundaries	Unclosed string literals are detected

What It Does NOT Check

• Provider-specific attribute requirements
• Resource argument types and constraints
• Variable type compatibility
• Module source availability
• State file consistency

For full semantic validation, use terraform init followed by terraform validate. The structural check here is a fast first pass that catches syntax errors without needing provider plugins.