Input Validation - Combine two or more variables

[galamiram]

Terraform

v0.12.26

Use-cases

When trying to enforce one variable is required not to be empty, if another variable is provided.

Attempted Solutions

variable "alias_record" {
  description = "The record name to associate with the RDS."
  type        = string
  default     = ""
}

variable "hosted_zone_name" {
  description = "The hosted zone name, where to create the alias record. Requieres if alias_record provided"
  type        = string
  default     = ""

  validation {
    condition     = var.alias_record != "" ? var.hosted_zone_name != "" : true
    error_message = "ERROR: hosted_zone_name can not be empty if alias_record provided."
  }
}

[galamiram]

It's solvable using an object:

variable "alias_record" {
  description = "The record name to associate with the RDS."
  type = object({
    record_name      = string,
    hosted_zone_name = string
  })
  default = {
    record_name      = ""
    hosted_zone_name = ""
  }

  validation {
    condition     = var.alias_record.record_name != "" ? var.alias_record.hosted_zone_name != "" : true
    error_message = "ERROR: alias_record.hosted_zone_name can not be empty if alias_record.record_name provided."
  }
}

Though I believe it would be useful to have this functionality.

[halberom]

seems to be related to #24374