TFNFR24 - Handling Deprecated Variables

Sometimes we will find names for some variable are not suitable anymore, or a change SHOULD be made to the data type. We want to ensure forward compatibility within a major version, so direct changes are strictly forbidden. The right way to do this is move this variable to an independent deprecated_variables.tf file, then redefine the new parameter in variable.tf and make sure it’s compatible everywhere else.

Deprecated variable MUST be annotated as DEPRECATED at the beginning of the description, at the same time the replacement’s name SHOULD be declared. E.g.,

variable "enable_network_security_group" {
  type        = string
  default     = null
  description = "DEPRECATED, use `network_security_group_enabled` instead; Whether to generate a network security group and assign it to the subnet. Changing this forces a new resource to be created."
}

A cleanup of deprecated_variables.tf SHOULD be performed during a major version release.