I have the next config.

main.tf

./modules/vpc

vpc.tf

./modules/compute_engine

ce.tf

on main I have

module "vpc" {
  source = "./modules/vpc"
}

module "compute_engine_controller" {
  source = "./modules/compute_engine"
  vpc_name = module.vpc.vpc_network_name
}

on vpc I have

output "vpc_network_name" {
  value = google_compute_network.vpc_network.name
}

on ce I have

resource "google_compute_instance" "controller" {
...
  network_interface {
    network = var.vpc_name
  }
...
}

I get an error

│ Error: Unsupported argument
│
│ on main.tf line 34, in module "compute_engine_controller":
│ 34: vpc_name = module.vpc.vpc_network_name
│
│ An argument named "vpc_name" is not expected here.

why?

>Solution :

Since the module is complaining about not expecting an argument called vpc_name, that means that the corresponding variable has not been defined in the variables.tf of the module. To fix this, what needs to be added is:

variable "vpc_name" {
  type        = string
  description = "The name of the VPC to be used."
}