Terraform Assertion

A simple module that asserts that a condition is true. The assertion is checked during planning, unless the condition depends on a value that will only be known during apply.

The module forces Terraform to fail if the condition is false by providing an invalid input to a Terraform function. It uses the error message in the invalid input so that the resulting Terraform failure message is descriptive (although it is slightly confusing in the format; see the example below).

Usage

module "assertion_unix_only" {
  source  = "Invicton-Labs/assertion/null"
  
  // The condition to ensure is TRUE
  // In this example, assert that the operating system uses forward slashes for path separators
  condition = dirname("/") == "/"
  
  // The error message to print out if the condition evaluates to FALSE
  error_message = "This Terraform configuration can only be run on Unix-based machines."
}

Output on Unix machines:

No changes. Your infrastructure matches the configuration.

Output on Windows machines:

// This is where you see the real error message
var.error_message is "This Terraform configuration can only be run on Unix-based machines."

// Ignore this part
There is no function named "SEE_ABOVE_ERROR_MESSAGE".