Terraform: Input Variable Checking

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Description:

Quick post here about how you can go about using Input Validation checks with Terraform variables.

To Resolve:

  1. A simple example with two values:

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    variable "region" {
   description = "(Optional) The name of the region. Example: West US."
   type        = string
   default     = "westus"

   validation {
      condition     = var.region == "westus" || var.region == "eastus"
      error_message = "The region must be westus or eastus."
   }
}

  2. An example with many values:

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    variable "sub_abbr" {
   description = <<EOF
   (Required) The abbreviated name of the subscription. Used for naming resources.
   Must be one of the following:
   abc  => subscription abc
   def  => subscription def
   ghi  => subscription ghi
   EOF
   
   type        = string
   
   validation {
   condition = (var.sub_abbr == "abc" ||
      var.sub_abbr == "def" ||
      var.sub_abbr == "ghi")
   error_message = "The subscription abbreviation must be one of: `abc,def,ghi` ."
}
}

  3. A cleaner way using contains:

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    variable "sub_abbr" {
   description = <<EOF
   (Required) The abbreviated name of the subscription. Used for naming resources.
   Must be one of the following:
   abc  => subscription abc
   def  => subscription def
   ghi  => subscription ghi
   EOF
   
   type        = string
   
   validation {
      condition     = contains(["abc","def","ghi"], var.sub_abbr)
      error_message = "The subscription abbreviation must be one of: `abc,def,ghi` ."
   }
}

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