Engine is required to validate the plan (#101)

Author: lechuk47

er_aws_rds/input.py

@@ -133,7 +133,7 @@ class Rds(RdsAppInterface):
 
     model_config = ConfigDict(extra="allow")
     identifier: str
-    engine: str | None = None
+    engine: str = "postgres"
     allow_major_version_upgrade: bool | None = False
     availability_zone: str | None = None
     monitoring_interval: int | None = None
@@ -191,12 +191,15 @@ def unset_az_if_multi_region(self) -> "Rds":
 
     @model_validator(mode="after")
     def unset_replica_or_snapshot_not_allowed_attrs(self) -> "Rds":
-        """Some attributes are not allowed if the instance is a replica or needs to be created from a snapshot"""
+        """
+        Some attributes are not allowed if the instance is a read replica or is created from a snapshot.
+
+        engine is not removed because it's needed in the plan validation.
+        """
         if self.replica_source or self.replicate_source_db or self.snapshot_identifier:
             self.username = None
             self.password = None
             self.name = None
-            self.engine = None
             self.allocated_storage = None
         return self
 

hooks/post_plan.py

@@ -89,7 +89,7 @@ def _validate_version_on_create(self) -> None:
         for u in self.aws_db_instance_creations:
             if not u.change or not u.change.after:
                 continue
-            engine = u.change.after["engine"]
+            engine = self.input.data.engine
             version = u.change.after["engine_version"]
             if not self.aws_api.is_rds_engine_version_available(
                 engine=engine, version=version

module/main.tf

@@ -41,9 +41,10 @@ resource "aws_iam_role_policy_attachment" "this" {
 }
 
 locals {
-  parameter_groups        = { for pg in try(var.parameter_groups, []) : pg.name => pg }
-  parameter_group_name    = try(var.rds_instance.parameter_group_name, null)
-  parameter_group_managed = local.parameter_group_name != null ? contains(keys(local.parameter_groups), local.parameter_group_name) : false
+  parameter_groups             = { for pg in try(var.parameter_groups, []) : pg.name => pg }
+  parameter_group_name         = try(var.rds_instance.parameter_group_name, null)
+  parameter_group_managed      = local.parameter_group_name != null ? contains(keys(local.parameter_groups), local.parameter_group_name) : false
+  aws_db_instance_needs_engine = try(var.rds_instance.replicate_source_db, null) == null && try(var.rds_instance.snapshot_identifier, null) == null ? true : false
 }
 
 resource "aws_db_parameter_group" "this" {
@@ -115,7 +116,7 @@ resource "aws_db_instance" "this" {
   domain_iam_role_name                  = try(var.rds_instance.domain_iam_role_name, null)
   domain_ou                             = try(var.rds_instance.domain_ou, null)
   enabled_cloudwatch_logs_exports       = try(var.rds_instance.enabled_cloudwatch_logs_exports, null)
-  engine                                = try(var.rds_instance.engine, null)
+  engine                                = local.aws_db_instance_needs_engine ? var.rds_instance.engine : null
   engine_version                        = try(var.rds_instance.engine_version, null)
   final_snapshot_identifier             = try(var.rds_instance.final_snapshot_identifier, null)
   iam_database_authentication_enabled   = try(var.rds_instance.iam_database_authentication_enabled, null)