terraform_data resource only shifts the problem, use null_data_source…

… instead

modules/ionos-mongodb-cluster/data.tf

@@ -1,4 +1,15 @@
 data "ionoscloud_mongo_template" "mongo_template" {
   count = var.resource_template == null ? 0 : 1
   name = var.resource_template
+}
+
+# Workaround
+# There's probably a bug in the IONOS Provider: The DataSource ionoscloud_mongo_template doesn't define id
+# as computed, leading to an inconsistent final plan (id is null instead of unknown in the initial plan)
+# This null_data_source is in between and the output is unknown in the initial plan, solving the problem.
+data "null_data_source" "template_workaround" {
+  inputs = {
+    mongo_template_id = var.resource_template == null ? null : data.ionoscloud_mongo_template.mongo_template[0].id
+  }
+  depends_on = [ data.ionoscloud_mongo_template.mongo_template ]
 }

modules/ionos-mongodb-cluster/main.tf

@@ -16,7 +16,7 @@ resource ionoscloud_mongo_cluster "mongo_cluster" {
     cidr_list     = local.cidrs
   }
 
-  template_id = terraform_data.template_id_workaround.output
+  template_id = data.null_data_source.template_workaround.outputs["mongo_template_id"]
   edition     = var.resource_template == null ? "enterprise" : null
 
   maintenance_window {
@@ -25,15 +25,6 @@ resource ionoscloud_mongo_cluster "mongo_cluster" {
   }
 }
 
-# Workaround
-# There's probably a bug in the IONOS Provider: The DataSource ionoscloud_mongo_template doesn't define id
-# as computed, leading to an inconsistent final plan (id is null instead of unknown in the initial plan)
-# This resource is in between and the output is unknown in the initial plan, solving the problem.
-resource "terraform_data" "template_id_workaround" {
-  input = var.resource_template == null ? null : data.ionoscloud_mongo_template.mongo_template[0].id
-  depends_on = [ data.ionoscloud_mongo_template.mongo_template ]
-}
-
 resource "ionoscloud_mongo_user" "initial_mongo_user" {
   for_each   = var.users
   cluster_id = ionoscloud_mongo_cluster.mongo_cluster.id