Changing the db_instance resource to mark the engine_version as Optional

builtin/providers/aws/resource_aws_db_instance.go

@@ -54,7 +54,7 @@ func resourceAwsDbInstance() *schema.Resource {
 
 			"engine_version": &schema.Schema{
 				Type:     schema.TypeString,
-				Required: true,
+				Optional: true,
 			},
 
 			"storage_encrypted": &schema.Schema{

builtin/providers/aws/resource_aws_db_instance_test.go

@@ -49,6 +49,25 @@ func TestAccAWSDBInstance_basic(t *testing.T) {
 	})
 }
 
+func TestAccAWSDBInstance_withoutEngineVersion(t *testing.T) {
+	var v rds.DBInstance
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckAWSDBInstanceDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: testAccAWSDBInstanceConfig,
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSDBInstanceExists("aws_db_instance.bar", &v),
+					testAccCheckAWSDBInstanceAttributes(&v),
+				),
+			},
+		},
+	})
+}
+
 func TestAccAWSDBInstanceReplica(t *testing.T) {
 	var s, r rds.DBInstance
 
@@ -194,6 +213,28 @@ resource "aws_db_instance" "bar" {
 	parameter_group_name = "default.mysql5.6"
 }`, rand.New(rand.NewSource(time.Now().UnixNano())).Int())
 
+var testAccAWSDBInstanceConfig_withoutEngineVersion = fmt.Sprintf(`
+resource "aws_db_instance" "bar" {
+	identifier = "foobarbaz-test-terraform-%d"
+
+	allocated_storage = 10
+	engine = "MySQL"
+	instance_class = "db.t1.micro"
+	name = "baz"
+	password = "barbarbarbar"
+	username = "foo"
+
+
+	# Maintenance Window is stored in lower case in the API, though not strictly
+	# documented. Terraform will downcase this to match (as opposed to throw a
+	# validation error).
+	maintenance_window = "Fri:09:00-Fri:09:30"
+
+	backup_retention_period = 0
+
+	parameter_group_name = "default.mysql5.6"
+}`, rand.New(rand.NewSource(time.Now().UnixNano())).Int())
+
 func testAccReplicaInstanceConfig(val int) string {
 	return fmt.Sprintf(`
 	resource "aws_db_instance" "bar" {

website/source/docs/providers/aws/r/db_instance.html.markdown

@@ -36,7 +36,7 @@ The following arguments are supported:
 
 * `allocated_storage` - (Required) The allocated storage in gigabytes.
 * `engine` - (Required) The database engine to use.
-* `engine_version` - (Required) The engine version to use.
+* `engine_version` - (Optional) The engine version to use.
 * `identifier` - (Required) The name of the RDS instance
 * `instance_class` - (Required) The instance type of the RDS instance.
 * `storage_type` - (Optional) One of "standard" (magnetic), "gp2" (general