providers/google: Add subnetwork_project field to enable cross-project networking in instance templates (#11110)

* Add subnetwork_project field to allow for XPN in GCE instance templates

* Missing os import

* Removing unneeded check

* fix formatting

* Add subnetwork_project to read

resource_compute_instance_template.go

@@ -203,6 +203,12 @@ func resourceComputeInstanceTemplate() *schema.Resource {
 							ForceNew: true,
 						},
 
+						"subnetwork_project": &schema.Schema{
+							Type:     schema.TypeString,
+							Optional: true,
+							ForceNew: true,
+						},
+
 						"access_config": &schema.Schema{
 							Type:     schema.TypeList,
 							Optional: true,
@@ -406,14 +412,16 @@ func buildNetworks(d *schema.ResourceData, meta interface{}) ([]*compute.Network
 	for i := 0; i < networksCount; i++ {
 		prefix := fmt.Sprintf("network_interface.%d", i)
 
-		var networkName, subnetworkName string
+		var networkName, subnetworkName, subnetworkProject string
 		if v, ok := d.GetOk(prefix + ".network"); ok {
 			networkName = v.(string)
 		}
 		if v, ok := d.GetOk(prefix + ".subnetwork"); ok {
 			subnetworkName = v.(string)
 		}
-
+		if v, ok := d.GetOk(prefix + ".subnetwork_project"); ok {
+			subnetworkProject = v.(string)
+		}
 		if networkName == "" && subnetworkName == "" {
 			return nil, fmt.Errorf("network or subnetwork must be provided")
 		}
@@ -435,8 +443,11 @@ func buildNetworks(d *schema.ResourceData, meta interface{}) ([]*compute.Network
 			if err != nil {
 				return nil, err
 			}
+			if subnetworkProject == "" {
+				subnetworkProject = project
+			}
 			subnetwork, err := config.clientCompute.Subnetworks.Get(
-				project, region, subnetworkName).Do()
+				subnetworkProject, region, subnetworkName).Do()
 			if err != nil {
 				return nil, fmt.Errorf(
 					"Error referencing subnetwork '%s' in region '%s': %s",
@@ -639,6 +650,7 @@ func flattenNetworkInterfaces(networkInterfaces []*compute.NetworkInterface) ([]
 			subnetworkUrl := strings.Split(networkInterface.Subnetwork, "/")
 			networkInterfaceMap["subnetwork"] = subnetworkUrl[len(subnetworkUrl)-1]
 			region = subnetworkUrl[len(subnetworkUrl)-3]
+			networkInterfaceMap["subnetwork_project"] = subnetworkUrl[len(subnetworkUrl)-5]
 		}
 
 		if networkInterface.AccessConfigs != nil {

resource_compute_instance_template_test.go

@@ -2,6 +2,7 @@ package google
 
 import (
 	"fmt"
+	"os"
 	"strings"
 	"testing"
 
@@ -115,6 +116,27 @@ func TestAccComputeInstanceTemplate_subnet_custom(t *testing.T) {
 	})
 }
 
+func TestAccComputeInstanceTemplate_subnet_xpn(t *testing.T) {
+	var instanceTemplate compute.InstanceTemplate
+	var xpn_host = os.Getenv("GOOGLE_XPN_HOST_PROJECT")
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckComputeInstanceTemplateDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: testAccComputeInstanceTemplate_subnet_xpn(xpn_host),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckComputeInstanceTemplateExists(
+						"google_compute_instance_template.foobar", &instanceTemplate),
+					testAccCheckComputeInstanceTemplateSubnetwork(&instanceTemplate),
+				),
+			},
+		},
+	})
+}
+
 func TestAccComputeInstanceTemplate_metadata_startup_script(t *testing.T) {
 	var instanceTemplate compute.InstanceTemplate
 
@@ -467,6 +489,45 @@ resource "google_compute_instance_template" "foobar" {
 	}
 }`, acctest.RandString(10), acctest.RandString(10), acctest.RandString(10))
 
+func testAccComputeInstanceTemplate_subnet_xpn(xpn_host string) string {
+	return fmt.Sprintf(`
+	resource "google_compute_network" "network" {
+		name = "network-%s"
+		auto_create_subnetworks = false
+		project = "%s"
+	}
+
+	resource "google_compute_subnetwork" "subnetwork" {
+		name = "subnetwork-%s"
+		ip_cidr_range = "10.0.0.0/24"
+		region = "us-central1"
+		network = "${google_compute_network.network.self_link}"
+		project = "%s"
+	}
+
+	resource "google_compute_instance_template" "foobar" {
+		name = "instance-test-%s"
+		machine_type = "n1-standard-1"
+		region = "us-central1"
+
+		disk {
+			source_image = "debian-8-jessie-v20160803"
+			auto_delete = true
+			disk_size_gb = 10
+			boot = true
+		}
+
+		network_interface {
+			subnetwork = "${google_compute_subnetwork.subnetwork.name}"
+			subnetwork_project = "${google_compute_subnetwork.subnetwork.project}"
+		}
+
+		metadata {
+			foo = "bar"
+		}
+	}`, acctest.RandString(10), xpn_host, acctest.RandString(10), xpn_host, acctest.RandString(10))
+}
+
 var testAccComputeInstanceTemplate_startup_script = fmt.Sprintf(`
 resource "google_compute_instance_template" "foobar" {
 	name = "instance-test-%s"
@@ -486,6 +547,6 @@ resource "google_compute_instance_template" "foobar" {
 	network_interface{
 		network = "default"
 	}
-	
+
 	metadata_startup_script = "echo 'Hello'"
 }`, acctest.RandString(10))