feat: add check-block for slug override assert

Author: tobiasehlert

README.md

@@ -92,6 +92,8 @@ postgresql_server = {
 You can override the slug for specific resources by using the `resource-slug-overrides` input map.
 Each key must match the resource output key (for example `analysis_services_server` or `api_management`).
 When provided, the override value is normalized to lowercase and then applied to `slug`, `name`, and `name_unique`.
+Override values that are empty or whitespace-only are rejected at plan time.
+Keys that do not match a known resource output key are ignored silently; a `check` assertion will surface a warning with the offending key names.
 
 ```tf
 module "naming" {
@@ -109,6 +111,7 @@ module "naming" {
 
 | Name | Version |
 |------|---------|
+| <a name="requirement_terraform"></a> [terraform](#requirement\_terraform) | >= 1.5.0 |
 | <a name="requirement_random"></a> [random](#requirement\_random) | >= 3.3.2 |
 
 ## Providers

main.tf

@@ -5,6 +5,7 @@ terraform {
       version = ">= 3.3.2"
     }
   }
+  required_version = ">= 1.5.0"
 }
 
 resource "random_string" "main" {
@@ -36,7 +37,7 @@ locals {
   slug_overrides_safe = {
     for resource_name, slug in var.resource-slug-overrides :
     resource_name => lower(trimspace(coalesce(slug, "")))
-    if trimspace(coalesce(slug, "")) != ""
+    if trimspace(coalesce(slug, "")) != "" && contains(keys(local.az_default), resource_name)
   }
   // Names based in the recomendations of
   // https://docs.microsoft.com/en-us/azure/cloud-adoption-framework/ready/azure-best-practices/naming-and-tagging
@@ -4227,3 +4228,10 @@ locals {
     }
   }
 }
+
+check "resource_slug_overrides_keys" {
+  assert {
+    condition     = length(setsubtract(keys(var.resource-slug-overrides), keys(local.az_default))) == 0
+    error_message = "resource-slug-overrides contains unknown resource key(s): ${join(", ", tolist(setsubtract(keys(var.resource-slug-overrides), keys(local.az_default))))}"
+  }
+}

templates/main.tmpl

@@ -28,6 +28,7 @@ terraform {
       version = ">= 3.3.2"
     }
   }
+  required_version = ">= 1.5.0"
 }
 
 resource "random_string" "main" {
@@ -59,7 +60,7 @@ locals {
   slug_overrides_safe = {
     for resource_name, slug in var.resource-slug-overrides :
     resource_name => lower(trimspace(coalesce(slug, "")))
-    if trimspace(coalesce(slug, "")) != ""
+    if trimspace(coalesce(slug, "")) != "" && contains(keys(local.az_default), resource_name)
   }
   // Names based in the recomendations of
   // https://docs.microsoft.com/en-us/azure/cloud-adoption-framework/ready/azure-best-practices/naming-and-tagging
@@ -84,4 +85,11 @@ locals {
     {{- end }}
   }
 }
+
+check "resource_slug_overrides_keys" {
+  assert {
+    condition     = length(setsubtract(keys(var.resource-slug-overrides), keys(local.az_default))) == 0
+    error_message = "resource-slug-overrides contains unknown resource key(s): ${join(", ", tolist(setsubtract(keys(var.resource-slug-overrides), keys(local.az_default))))}"
+  }
+}
 {{ end }}