How to use the default value in Terraform when the corresponding environment variable exists?

Question

I have a TF variable:

variable "test" {
  type = number
  default = 1
}

I want Terraform to use the specified default value 1 when I pass the TF_VAR_test variable with an empty value.

Trying this way

TF_VAR_test= terraform plan

fails with

│ Error: Invalid value for input variable
│ 
│ The environment variable TF_VAR_test does not contain a valid
│ value for variable "test": a number is required.

How can I use the default value if the environment variable exists and is empty?

Answer 1

In that case you can't use a type. Empty string is not a number . Instead, you can do the following:

variable "test" {
  default = 1
  validation {
      condition =  var.test != "" && can(tonumber(var.test))
      error_message = "Only number of emptry string are accepted."
  }
}

locals {
    test_value = coalesce(tonumber(var.test), 1)
}

And then you use local.test_value later on.

Answer 2

use local and if statement

variable "test" {
  type    = string
  default = "defaultValue"
}
locals {
  test = var.test != "" ? var.test : "defaultValue"
}

output "name" {
  value = local.test
}