I’m new to Terraform, and I’m trying to handle creating/accessing a resource group. In our staging environment, the resource group was created manually via the Azure console, and I want to access it in Terraform via a data block, as so:

data "azurerm_resource_group" "my_rg" {
  name = "existing_staging_rg_name"
}

However, in our dev env, this resource group doesn’t exist yet, so I plan to create it via a module block, in order to use my company’s repo of pre-approved published TF modules:

module "my_rg" {
  source = "github.com/org-name/module-that-creates-an-rg-repo-name"
  # Additional input vars...
}

My questions are:

1. How can I ensure that only one of the above blocks is executed, depending on the env?
2. How can I access this resource group uniformly from other modules? I.e. if the env is staging, I want to use data.azurerm_resource_group.my_rg.name, in dev I want to use module.my_rg.rg_name.