how to variablize the resource attribute as input value in terraform

I am trying to use below code

data "azurerm_resource_group" "rg_tst_na" {
  name     = "test1"
}

data "azurerm_resource_group" "rg_dev_na" {
  name     = "test2"
}

resource "azurerm_role_assignment" "test_role_assign" {
  for_each = var.test_role_assignment
  principal_id         = azurerm_user_assigned_identity.test_setup["${each.key}_${each.value}"].principal_id # this is created as separate resource using a for_each loop this resource is validate by terraform apply
  role_definition_name = "Network Contributor"          
  scope                = data.azurerm_resource_group."${each.key}_${each.value}".id
}

variable "var.test_role_assignment" {
  type = map(string)
  default={
    "na" = "dev",
    "na" = "tst",    
  }
}

I am getting error that scope cannot be read during terraform plan, how can I variablize the input of resource attribute

  scope = data.azurerm_resource_group.rg_"${each.value}"_"${each.key}".id

Is this possible?

Can I use variable in the value of scope as resource attribute but variablized? Is this violation of terraform rules

There are a couple of things to note:

1. variable "var.test_role_assignment" should be only variable "test_role_assignment"
2. The other part you are asking about, scope, that's not how terraform works and cannot be done.

However, you could use the same for_each for the data source, and reference that in the resource block. Something along the lines should work:

data "azurerm_resource_group" "rg_na" {
 for_each = var.test_role_assignment
 name     = each.value
}

resource "azurerm_role_assignment" "test_role_assign" {
  for_each             = var.test_role_assignment
  principal_id         = azurerm_user_assigned_identity.test_setup["${each.key}_${each.value}"].principal_id # this is created as separate resource using a for_each loop this 
resource is validate by terraform apply
  role_definition_name = "Network Contributor"          
  scope                = data.azurerm_resource_group.rg_na[each.key].id
}

variable "test_role_assignment" {
  type    = map(string)
  default = {
    "na" = "dev",
    "na" = "tst",    
  }
}