Terraform validation builder
A Terraform variable validation generator creates copy-ready validation blocks that catch bad module inputs before a plan runs. Use this free tool to generate allowed values, regex checks, length rules, required map keys, examples, and clear error messages.
Choose a rule set, then tune the generated Terraform validation block.
Terraform variable environment
variable "environment" {
description = "Deployment environment for this workspace."
type = string
default = "dev"
nullable = false
validation {
condition = var.environment != null &&
contains(["dev", "staging", "production"], var.environment) &&
length(var.environment) >= 2 &&
length(var.environment) <= 24 &&
can(regex("^[a-z][a-z0-9-]*$", var.environment))
error_message = "Environment must be dev, staging, or production."
}
}
# Example usage
module "service" {
source = "./modules/service"
environment = "dev"
}
# Validation checklist
# 1. Run terraform fmt.
# 2. Run terraform validate.
# 3. Test one passing value and one failing value in a sandbox plan.Keep error messages specific so plan failures are actionable.
Use can(regex()) to avoid hard failures before validation returns.
Prefer allow lists for environments, sizes, regions, and tag keys.
Variable validation is the first guardrail module consumers see. It can reject unsupported environments, invalid names, malformed CIDR ranges, missing tag keys, or version strings before provider APIs return harder-to-read errors.
Keep validations focused on module contracts. Provider limits, security policies, and organization rules should still be tested with terraform validate, plan checks, and CI policy gates.
A Terraform variable validation generator creates copy-ready validation blocks that check input values before a plan or apply runs.
Use validation for values with clear rules, such as environments, naming patterns, regions, allowed sizes, CIDR ranges, versions, and required tag keys.
Yes. Terraform validation can use regex with can() so invalid input returns a helpful validation error instead of breaking expression evaluation.
No. Add validation when the rule prevents real mistakes. Avoid complex rules that duplicate provider behavior or make modules hard to reuse.
A good error message states the accepted format or value list and tells the caller exactly how to fix the input.
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