Resource Group variable should accept entire resource_group object

[troyready]

Passing in the resource_group name only and relying on depends_on on the module causes lifecycle issues for the resources in this module. E.g., if the tags on the resource group are changed then the subnets will be replaced (because of a new computed location attribute on the resource group data_source in the module).

Martin's recommendation is that:

In current versions of Terraform we generally recommend that a specific configuration should either be managing an object or reading the object using a date resource, but not both at the same time.

He then details what a variable design would be that avoids this issue:

variable "resource_group" {
  type = object({
    name     = string
    location = string
  })
}

Able to be consumed like:

provider "azurerm" {
  features {}
}

resource "azurerm_resource_group" "example" {
  name     = "my-resources"
  location = "West Europe"
}

module "vnet" {
  source              = "Azure/vnet/azurerm"
  resource_group      = azurerm_resource_group.example
  address_space       = ["10.0.0.0/16"]
  subnet_prefixes     = ["10.0.1.0/24", "10.0.2.0/24", "10.0.3.0/24"]
  subnet_names        = ["subnet1", "subnet2", "subnet3"]

  subnet_service_endpoints = {
    subnet2 = ["Microsoft.Storage", "Microsoft.Sql"],
    subnet3 = ["Microsoft.AzureActiveDirectory"]
  }

  tags = {
    environment = "dev"
    costcenter  = "it"
  }

}

This would obviously be a breaking change to the module (requiring a major version bump), but it wouldn't be hazardous to users: accidental upgrades would cause an error that the new variable is missing, allowing them to update the variable and continue using the module.

[lonegunmanb]

Thanks @troyready for opening this issue. I'm closing it since it has been fixed by #72. Please feel free to reopen it if you have any further question.