Generate file with dynamic content with Terragrunt - terraform

Question

I'm really new to Terragrunt.
I was wondering if there is a way to dynamically generate the content of a file?
For example, consider the following piece of code:
generate "provider" {
path = "provider.tf"
if_exists = "overwrite"
contents = <<EOF
terraform {
required_providers {
azurerm = {
source = "azurerm"
version = "=2.49.0"
}
}
}
provider "azurerm" {
features {}
subscription_id = "xxxxxxxxxxxxxxxxx"
}
EOF
}
Is there a way to set values such as subscription_id dynamically? I've tried using something like ${local.providers.subscription_id} but it doesn't work:
provider "azurerm" {
features {}
subscription_id = "${local.providers.subscription_id}"
}

Answer 1

What you have there should work exactly as is, so long as you define the local in the same scope. Just tested the following with Terragrunt v0.28.24.
In common.hcl, a file located in some parent directory (but still in the same Git repo):
locals {
providers = {
subscription_id = "foo"
}
}
In your terragrunt.hcl:
locals {
common_vars = read_terragrunt_config(find_in_parent_folders("common.hcl"))
}
generate "provider" {
path = "provider.tf"
if_exists = "overwrite"
contents = <<EOF
terraform {
required_providers {
azurerm = {
source = "azurerm"
version = "=2.49.0"
}
}
}
provider "azurerm" {
features {}
subscription_id = "${local.common_vars.locals.providers.subscription_id}"
}
EOF
}
After I run terragrunt init, the provider.tf is generated with the expected contents:
provider "azurerm" {
features {}
subscription_id = "foo"
}