Terraform Validate and fmt

This lesson explains how to use terraform validate and terraform fmt to catch configuration errors early and enforce consistent HCL (HashiCorp Configuration Language) formatting.

Overview

terraform validate performs static validation of Terraform configuration files. When run after terraform init, it loads provider schemas and checks configuration structure and types against those schemas.
terraform fmt reformats HCL files to the canonical style defined by HashiCorp. It changes only formatting (whitespace, indentation) and does not alter any configuration logic.

Both commands are fast and lightweight and are ideal for local development checks and CI pipelines.

terraform validate — static validation (syntax + provider schema)

terraform validate parses your configuration, checks HCL syntax, and — if you previously ran terraform init — uses provider schemas to validate resource and argument names and types. Important: run terraform init first so Terraform can download provider plugins and schema information. Without initialization, terraform validate still checks basic HCL syntax but may not catch provider-specific schema errors. Example: an Azure Storage Account resource with a subtle argument-name typo

resource "azurerm_storage_account" "example" {
  name                          = var.storage_account_name
  location                      = "East US"
  resource_group_name           = "my-workshop-eus-rg"
  account_tier                  = "Standard"
  account_replication_types     = "LRS"
  public_network_access_enabled = false
}

At a glance the block looks valid, but the correct argument name is account_replication_type (singular). The typo results in a missing required argument plus an unsupported unexpected argument. After running terraform init and terraform validate, Terraform will detect both issues and report file/line numbers with suggestions:

$ terraform validate
Error: Missing required argument

  on main.tf line 1, in resource "azurerm_storage_account" "example":
   1: resource "azurerm_storage_account" "example" {

The argument "account_replication_type" is required, but no definition was found.

Error: Unsupported argument

  on main.tf line 6, in resource "azurerm_storage_account" "example":
   6:   account_replication_types     = "LRS"

An argument named "account_replication_types" is not expected here.
Did you mean "account_replication_type"?

Key characteristics of terraform validate:

Validates HCL syntax and configuration structure.
When initialized, validates against provider schemas (argument names, types, required fields).
Does not make API calls to create or modify cloud resources — no infrastructure changes.
Excellent to use in pre-commit hooks and CI pipelines to catch schema and syntax problems early.

Run terraform init before terraform validate to ensure provider schemas are available for full validation.

terraform fmt — enforce consistent HCL formatting

terraform fmt reformats your Terraform configuration files to the canonical HCL style. This improves readability and reduces noisy diffs in version control. It does not check correctness or change resource semantics. Example of a poorly formatted file:

resource "azurerm_storage_account" "example" {
  name                        = var.storage_account_name
  location                    = "East US"
  resource_group_name         = "my-workshop-eus-rg"
  account_tier                = "Standard"
  account_replication_type    = "LRS"
  public_network_access_enabled = false
}

Format the file with:

$ terraform fmt main.tf

For CI pipelines, use terraform fmt -check to verify that files are already formatted and fail the build if they are not:

$ terraform fmt -check

Notes about terraform fmt:

Only modifies whitespace/indentation and formatting.
Does not validate argument names, types, or provider schemas.
Useful as an automatic pre-commit hook step or CI gate to enforce a consistent code style.

terraform validate does not check runtime constraints or whether a given resource name is already taken by the cloud provider. Those checks require interacting with the provider (for example via terraform plan/apply or provider APIs).

Quick reference

Command	Purpose	CI usage
`terraform init`	Download provider plugins and initialize the working directory.	Always run before `validate` in CI.
`terraform validate`	Static validation of HCL and (after init) provider-schema checks.	Run to catch schema/syntax errors early.
`terraform fmt`	Reformat files to canonical HCL style.	Use `terraform fmt -check` to enforce formatting in CI.

Best practices

Always run terraform init once per working directory (or in your CI job) before terraform validate.
Add terraform fmt -check and terraform validate to CI pipelines to block malformed or invalid configs.
Use terraform fmt as a pre-commit hook to keep repository diffs clean and consistent.
Remember that terraform validate is static — to confirm resource creation and runtime constraints, use terraform plan and terraform apply in a safe environment.

Links and references

Summary:

Use terraform validate to catch syntax and provider-schema issues before planning/applying.
Use terraform fmt to enforce consistent HCL formatting across your team.
Both commands are quick and should be part of your standard Terraform workflow (locally and in CI) before running terraform plan or terraform apply.

We’ll now cover another Terraform command.

Introduction

Infrastructure as Code Fundamentals

Terraform Cloud

Setting up environment

Azure Context for Terraform

HashiCorp Configuration Language

Terraform Providers

Variables

Outputs and Dependencies

Iteration and Logic

Advanced Constructs

Terraform State Fundamentals

Remote State

Terraform Workspaces

Terraform CLI

Lifecycle Meta-Arguments

Data Sources

Provisioners

Debugging Terraform

Terraform Modules

Azure DevOps Integration

Azure Pipelines for Terraform

Terraform Validate and fmt

Overview

terraform validate — static validation (syntax + provider schema)

terraform fmt — enforce consistent HCL formatting

Quick reference

Best practices

Links and references

Watch Video

​Overview

​terraform validate — static validation (syntax + provider schema)

​terraform fmt — enforce consistent HCL formatting

​Quick reference

​Best practices

​Links and references

Watch Video

Overview

terraform validate — static validation (syntax + provider schema)

terraform fmt — enforce consistent HCL formatting

Quick reference

Best practices

Links and references