fix: return SubnetArn and AWS's default subnet fields from CreateSubnet and DescribeSubnets

spinifex/handlers/ec2/vpc/service_impl.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/service/ec2"
+	"github.com/mulgadc/spinifex/spinifex/arn"
 	"github.com/mulgadc/spinifex/spinifex/awserrors"
 	"github.com/mulgadc/spinifex/spinifex/config"
 	"github.com/mulgadc/spinifex/spinifex/filterutil"
@@ -132,6 +133,15 @@ func (s *VPCServiceImpl) localAZ() string {
 	return s.config.AZ
 }
 
+// region returns the configured AWS region, falling back to the default when
+// no config or region is wired.
+func (s *VPCServiceImpl) region() string {
+	if s.config == nil || s.config.Region == "" {
+		return config.DefaultAWSRegion
+	}
+	return s.config.Region
+}
+
 // NewVPCServiceImplWithNATS creates a VPC service with NATS JetStream for persistence.
 func NewVPCServiceImplWithNATS(ctx context.Context, cfg *config.Config, natsConn *nats.Conn) (*VPCServiceImpl, error) {
 	js, err := jetstream.New(natsConn)
@@ -1265,6 +1275,18 @@ func (s *VPCServiceImpl) subnetRecordToEC2(record *SubnetRecord, availableIPs in
 		AvailableIpAddressCount: aws.Int64(int64(availableIPs)),
 		OwnerId:                 aws.String(accountID),
 		MapPublicIpOnLaunch:     aws.Bool(record.MapPublicIpOnLaunch),
+		SubnetArn:               aws.String(arn.FormatEC2(arn.EC2Subnet, s.region(), accountID, record.SubnetId)),
+		// Spinifex subnets are IPv4-only with no customer-owned pool, and
+		// instances are named ip-<a-b-c-d> with no resource-name records.
+		AssignIpv6AddressOnCreation: aws.Bool(false),
+		EnableDns64:                 aws.Bool(false),
+		Ipv6Native:                  aws.Bool(false),
+		MapCustomerOwnedIpOnLaunch:  aws.Bool(false),
+		PrivateDnsNameOptionsOnLaunch: &ec2.PrivateDnsNameOptionsOnLaunch{
+			HostnameType:                    aws.String(ec2.HostnameTypeIpName),
+			EnableResourceNameDnsARecord:    aws.Bool(false),
+			EnableResourceNameDnsAAAARecord: aws.Bool(false),
+		},
 	}
 
 	subnet.Tags = utils.MapToEC2Tags(record.Tags)

spinifex/handlers/ec2/vpc/service_impl_test.go

@@ -287,6 +287,44 @@ func TestCreateSubnet(t *testing.T) {
 	assert.Equal(t, int64(251), *out.Subnet.AvailableIpAddressCount)
 }
 
+// TestSubnetResponse_AWSDefaultFields checks the ARN and the fields AWS
+// reports for a new subnet, on both the create and describe paths.
+func TestSubnetResponse_AWSDefaultFields(t *testing.T) {
+	t.Parallel()
+	svc := setupTestVPCService(t)
+	svc.config = &config.Config{Region: "ap-southeast-2"}
+	vpcID := createTestVPC(t, svc, "10.0.0.0/16")
+
+	out, err := svc.CreateSubnet(context.Background(), &ec2.CreateSubnetInput{
+		VpcId:     aws.String(vpcID),
+		CidrBlock: aws.String("10.0.1.0/24"),
+	}, testAccountID)
+	require.NoError(t, err)
+	desc, err := svc.DescribeSubnets(context.Background(), &ec2.DescribeSubnetsInput{
+		SubnetIds: []*string{out.Subnet.SubnetId},
+	}, testAccountID)
+	require.NoError(t, err)
+	require.Len(t, desc.Subnets, 1)
+
+	for name, subnet := range map[string]*ec2.Subnet{"create": out.Subnet, "describe": desc.Subnets[0]} {
+		assert.Equal(t, "arn:aws:ec2:ap-southeast-2:"+testAccountID+":subnet/"+*out.Subnet.SubnetId, aws.StringValue(subnet.SubnetArn), name)
+		for field, v := range map[string]*bool{
+			"AssignIpv6AddressOnCreation": subnet.AssignIpv6AddressOnCreation,
+			"EnableDns64":                 subnet.EnableDns64,
+			"Ipv6Native":                  subnet.Ipv6Native,
+			"MapCustomerOwnedIpOnLaunch":  subnet.MapCustomerOwnedIpOnLaunch,
+		} {
+			require.NotNil(t, v, "%s %s", name, field)
+			assert.False(t, *v, "%s %s", name, field)
+		}
+		assert.Equal(t, &ec2.PrivateDnsNameOptionsOnLaunch{
+			HostnameType:                    aws.String("ip-name"),
+			EnableResourceNameDnsARecord:    aws.Bool(false),
+			EnableResourceNameDnsAAAARecord: aws.Bool(false),
+		}, subnet.PrivateDnsNameOptionsOnLaunch, name)
+	}
+}
+
 func TestCreateSubnet_MissingVpcId(t *testing.T) {
 	t.Parallel()
 	svc := setupTestVPCService(t)