Error about variable not declared on root module

[Tiago-SD]

Hello everyone,

I'm currently facing an error and not sure how to deal with it, because I know what is intended but can't see why it is happening on this specific case.

I'm using Terragrunt and starting on version 0.69.0 it starts to use TFLint v0.50.3. On that version It starts to give the following error:

Error

Variable assigned, but the root module does not declare a variable of that name.

Example

Error: Value for undeclared variable

  on <value for var.private_subnet> line 1:
  (source code not available)

A variable named "private_subnet" was assigned, but the root module does not declare a variable of that name.

Declaration

# stacks/dev/env.hcl

locals {
  environment    = "dev"
  instance_type  = "t2.micro"
  key_pair_name  = "Tiago-Playground"
  ec2_sg         = "sg-02e0f64609fb51b12"
  private_subnet = "subnet-07dd094ef8758b766"
}

Utilization

# stacks/dev/eu-west-1/ec2/terragrunt.hcl

include "root" {
  path   = find_in_parent_folders("root.hcl")
  expose = true
}

include "common" {
  path = "${dirname(find_in_parent_folders("root.hcl"))}/_common/ec2/ec2.hcl"
}

locals {
  environment_vars = read_terragrunt_config(find_in_parent_folders("env.hcl"))
  environment      = local.environment_vars.locals.environment
  instance_type    = local.environment_vars.locals.instance_type
  key_pair_name    = local.environment_vars.locals.key_pair_name
  ec2_sg           = local.environment_vars.locals.ec2_sg
  private_subnet   = local.environment_vars.locals.private_subnet
}

inputs = {
  instance_type          = local.instance_type
  key_name               = local.key_pair_name
  vpc_security_group_ids = [local.ec2_sg]
  subnet_id              = local.private_subnet

  tags = {
    Terraform   = "true"
    environment = local.environment
  }
}

# _common/ec2/ec2.hcl

terraform {
  source = "${local.terraform_module_source}?version=${local.terraform_module_version}"
}

locals {
  terraform_module_source  = "tfr:///terraform-aws-modules/ec2-instance/aws"
  terraform_module_version = "5.7.1"
}

inputs = {
  name       = "single-instance"
  monitoring = true
}

Example Repo

https://github.com/Tiago-SD/terragrunt-test

---

I hope I could make it somehow clear what is the issue I'm facing.

Thank you in advance for the support,
Tiago

[bendrucker]

Variables passed with --var must be declared in Terraform. TFLint didn't enforce that until #1941.

TFLint has also long supported the same TF_VAR_* environment variables that Terraform does. Unlike those specified via var files or flags, these are not required to exist in the module.

Which is appropriate depends on the context. You should generally prefer the var file/flag forms, since they protect against simple things like typos in variable names. But if your goal is to provide many variables, some of which aren't valid, you'll need to use the environment variable form. If you already have to call Terraform with TF_VAR_* because of this, you/Terragrunt should do the same for TFLint.

[Tiago-SD]

The variables tflint is complaining that are not being declared on the root module in fact are, but as locals. I'm using Terragrunt where we have a file called env.hcl where we are declaring all environment specific variables. It looks like it is ignoring what is inside locals {}.

[bendrucker]

This doesn't make sense:

in fact are, but as locals

Locals and variables are two different things. Variable values can be set with a varfile.

The error you have refers to a variable being set without a corresponding variable block.

[bendrucker]

Ultimately all that matters is what input variables you pass which is apparently inputs in Terragrunt. The locals and includes are distractions/indirection. The error ultimately means you are setting an input variable that the module doesn't declare.