Terraform – How to restrict an input variable to a list of possible choices

Stumbled across this question.

Since v0.13.0 input validation has been possible directly via the input variables. Thus you can actually achieve this with a snippet such as below.

variable "test_variable" {
  type        = string
  description = "some test value"

  validation {
    condition     = contains(["item1", "item2", "item3"], var.test_variable)
    error_message = "Valid values for var: test_variable are (item1, item2, item3)."
  } 
}

Read more here – https://www.hashicorp.com/blog/custom-variable-validation-in-terraform-0-13