Terraform: null values and for_each

Null values don’t go well hand in hand with Terraform’s for_each, but, as always, here’s some hack on how to get through.

Prerequisites

• Terraform

Solution

Personally, I’ve used null values in conditionals, being part of a dynamic blocks so to speak. Here’s some example though:

using tolist() function in a dynamic resource block

# variables.tf
variable "enable_access_config" {
  description = "Access configurations, i.e. IPs via which this instance can be accessed via the Internet."
  type        = string
  default     = null
}

# module.tf
resource "google_compute_instance" "this" {
  ...
  network_interface {
    subnetwork         = var.subnetwork
    subnetwork_project = var.subnetwork_project

    dynamic "access_config" {
      for_each = var.enable_access_config == null ? [] : tolist([var.enable_access_config])

      content {}
    }
  }
  ...
}

# main.tf 
module "vms" {
  ...
  enable_access_config = "true"
}

Conclusion

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