Why do I get The argument "env" is required, but no definition was found?

Question

I have the following directory/files structure:

.
├── main.tf
├── modules
│ └── Resource_group
│ ├── main.tf
│ └── vars.tf

Configuration files

./main.tf

module "app-rg" {
  source = "./modules/Resource_Group"
}

./modules/resource_group/main.tf

provider "azurerm" {
  version = "=2.11.0"
  features { }
}

resource "azurerm_resource_group" "rg" {
  name = "${lookup(var.resource_group, var.env)}"
  location = "${lookup(var.location, var.env)}"
}

./modules/resource_group/vars.tf

variable "env" {
  description = "env : dev or prod"
}

variable "resource_group" {
  type = "map"
  default = {
    dev = "rg-dev"
    prod = "rg-prod"
  }
}

variable "location" {
  type = "map"
  default = {
    dev = "westindia"
    prod = "westeurope"
  }
}

When I run a "terraform plan" I will get a below error.

Error: Missing required argument

on main.tf line 6, in module "app-rg": 6: module "app-rg" {

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

Why do I get The argument "env" is required, but no definition was found?

Solution

You have not provided the env input variable.

As there is no default value present, terraform doesn't know what env you want to use. You have a couple of options to fix that. First, you can include the variable value in the main.tf when calling a module. It would look like that:

module "app-rg" {
source = "./modules/Resource_Group"
env = "dev"
}

You can also include this input variable in a external variable definition file like terraform.tfvars, or pass it as an environmental variable, or set a default value in /modules/resource_group/vars.tf

Here are some resources on variables and modules by HasiCorp:

• https://learn.hashicorp.com/terraform/getting-started/variables
• https://learn.hashicorp.com/terraform/modules/using-modules
• https://www.terraform.io/docs/configuration/modules.html#calling-a-child-module

Comments

[ydaetskcoR]

The error is telling you that your module has env as a required, non defaulted argument and you haven't provided it when calling the module (you only pass the source argument to link to the module and no other arguments).