Optional and required properties for object variable when default is {}

I have the following variable maintenance_window_auto_upgrade that defaults to {}. My issue is Terraform throws an error as it expects the non-optional properties duration, frequency, and interval to be supplied. The exact error I get is below. What is the correct way to have the variable be optional while still supporting the required properties when maintenance_window_auto_upgrade is supplied? Also below is how I expect to use this variable with the azurerm_kubernetes_cluster resource. Thanks!

“This default value is not compatible with the variable’s type constraint: attributes “duration”, “frequency”, and “interval” are required.”

variable "maintenance_window_auto_upgrade" {
  type = object({
    day_of_week = optional(string) 
    duration    = number 
    frequency   = string 
    interval    = number
    start_date  = optional(string)
    start_time  = optional(string)
    utc_offset  = optional(string)
    week_index  = optional(string) 
    not_allowed = optional(list(object({
      end   = string 
      start = string 
    })), [])

  default = {}
  description = "Use Planned Maintenance to schedule and control upgrades for your Azure Kubernetes Service (AKS) cluster."

  validation { # day_of_week
    condition = contains(["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"], var.maintenance_window_auto_upgrade.day_of_week)
    error_message = "day_of_week must be one of 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', or 'Sunday'."
  validation { # week_index
    condition = contains(["First", "Second", "Third", "Fourth", "Last"], var.maintenance_window_auto_upgrade.week_index)
    error_message = "week_index must be one of 'First', 'Second', 'Third', 'Fourth', or 'Last'."
  validation { # frequency
    condition = contains(["Weekly", "AbsoluteMonthly", "RelativeMonthly"], var.maintenance_window_auto_upgrade.frequency)
    error_message = "frequency must be one of 'Weekly', 'AbsoluteMonthly', or 'RelativeMonthly'."
  validation { # duration
    condition = (
      var.maintenance_window_auto_upgrade.duration >= 4 &&
      var.maintenance_window_auto_upgrade.duration <= 24
    error_message = "day_of_month must be between 4 and 24."

// example showing variable usage
resource "azurerm_kubernetes_cluster" "aks" {
  name = var.name

  dynamic "maintenance_window_auto_upgrade" {
    for_each = var.maintenance_window_auto_upgrade != null ? [var.maintenance_window_auto_upgrade] : []

    content {
      day_of_week = maintenance_window_auto_upgrade.value["day_of_week"]
      duration    = maintenance_window_auto_upgrade.value["duration"]
      frequency   = maintenance_window_auto_upgrade.value["frequency"]
      interval    = maintenance_window_auto_upgrade.value["interval"]
      start_date  = maintenance_window_auto_upgrade.value["start_date"]
      start_time  = maintenance_window_auto_upgrade.value["start_time"]
      utc_offset  = maintenance_window_auto_upgrade.value["utc_offset"]
      week_index  = maintenance_window_auto_upgrade.value["week_index"]
      dynamic "not_allowed" {
      for_each = length(maintenance_window_auto_upgrade.value["not_allowed"]) > 0 ? maintenance_window_auto_upgrade.value["not_allowed"] : []

        content {
          end   = not_allowed.value["end"]
          start = not_allowed.value["start"]

Hi @joeypiccola,

I think what you need to answer first is: what do you expect for the value of duration, frequency, and interval in the default value? If they are not optional, then you must supply them somehow in the given object. If there is no valid default, then that means there really isn’t a valid default for the variable as a whole either, and the default should be left out.

hi @jbardin, I just noticed your reply, sorry about that. I ended up taking out the defaults. I was trying to do too many things at once. Thanks for the input!