Merge pull request #17755 from hashicorp/b-db-instance-forcenew-confi…

…cts-snapshot-id

r/db_instance: update plan-time validation for snapshot_identifier/name/username

.changelog/17755.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_db_instance: Fix conflicting argument validation error
+```

aws/resource_aws_db_instance.go

@@ -1,7 +1,6 @@
 package aws
 
 import (
-	"context"
 	"fmt"
 	"log"
 	"regexp"
@@ -12,7 +11,6 @@ import (
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/service/rds"
 	"github.com/hashicorp/aws-sdk-go-base/tfawserr"
-	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/customdiff"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/validation"
@@ -415,10 +413,9 @@ func resourceAwsDbInstance() *schema.Resource {
 			},
 
 			"snapshot_identifier": {
-				Type:          schema.TypeString,
-				Optional:      true,
-				ForceNew:      true,
-				ConflictsWith: []string{"username"},
+				Type:     schema.TypeString,
+				Optional: true,
+				ForceNew: true,
 			},
 
 			"auto_minor_version_upgrade": {
@@ -532,20 +529,6 @@ func resourceAwsDbInstance() *schema.Resource {
 
 			"tags": tagsSchema(),
 		},
-
-		CustomizeDiff: customdiff.All(
-			func(_ context.Context, diff *schema.ResourceDiff, v interface{}) error {
-				if _, ok := diff.GetOk("snapshot_identifier"); ok {
-					switch strings.ToLower(diff.Get("engine").(string)) {
-					case "mysql", "postgres", "mariadb":
-						if _, ok := diff.GetOk("name"); ok {
-							return fmt.Errorf("name attribute is not supported with snapshot_identifier when engine is %s", diff.Get("engine").(string))
-						}
-					}
-				}
-				return nil
-			},
-		),
 	}
 }
 
@@ -911,7 +894,14 @@ func resourceAwsDbInstanceCreate(d *schema.ResourceData, meta interface{}) error
 		}
 
 		if attr, ok := d.GetOk("name"); ok {
-			opts.DBName = aws.String(attr.(string))
+			// "Note: This parameter [DBName] doesn't apply to the MySQL, PostgreSQL, or MariaDB engines."
+			// https://docs.aws.amazon.com/AmazonRDS/latest/APIReference/API_RestoreDBInstanceFromDBSnapshot.html
+			switch strings.ToLower(d.Get("engine").(string)) {
+			case "mysql", "postgres", "mariadb":
+				// skip
+			default:
+				opts.DBName = aws.String(attr.(string))
+			}
 		}
 
 		if attr, ok := d.GetOk("allocated_storage"); ok {

aws/resource_aws_db_instance_test.go

@@ -4575,6 +4575,8 @@ resource "aws_db_instance" "mysql_restore" {
 
   instance_class          = data.aws_rds_orderable_db_instance.test.instance_class
   allocated_storage       = 20
+  username                = "root"
+  password                = "password"
   engine                  = data.aws_rds_orderable_db_instance.test.engine
   engine_version          = "5.6.41"
   backup_retention_period = 0