How to fix Error: Missing required argument in Terraform

The error output will tell you:
- The exact argument name that's missing
- The resource or module type
- The file and line number

Example:

Error: Missing required argument

on main.tf line 5, in resource "aws_instance" "example":
  5: resource "aws_instance" "example" {

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

Look up the resource or module you're using in the official documentation:

1. For built-in resources: Visit the Terraform provider documentation (e.g., terraform.io/docs/providers/aws/r/instance)
2. For modules: Check the module's README or source repository
3. Look at the 'Required' or 'Arguments' section

Note the required arguments and their expected types and formats.

Add the missing argument to the resource or module block. Make sure you use the correct argument name and provide a valid value.

Example for a missing ami argument:

resource "aws_instance" "example" {
  ami           = "ami-12345678"  # Add this
  instance_type = "t2.micro"
}

For module inputs:

module "vpc" {
  source  = "./modules/vpc"
  cidr    = "10.0.0.0/16"        # Add this
  region  = "us-east-1"
}

Run terraform validate to check your configuration syntax and required arguments:

terraform validate

This will catch missing required arguments without applying changes. Fix any errors and re-run validate until it passes.

If you recently upgraded a provider, some arguments may have become required:

# Check current provider versions
terraform version

# Update to latest provider versions
terraform init -upgrade

After upgrading, run terraform validate again to see if new required arguments are needed.