Make compute subnetwork ipv6_access_type field updatable

.changelog/6928.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+compute: Made subnetwork ipv6_access_type field updatable
+```

google/resource_compute_subnetwork.go

@@ -111,7 +111,6 @@ creation time.`,
 			"ipv6_access_type": {
 				Type:         schema.TypeString,
 				Optional:     true,
-				ForceNew:     true,
 				ValidateFunc: validateEnum([]string{"EXTERNAL", "INTERNAL", ""}),
 				Description: `The access type of IPv6 address this subnet holds. It's immutable and can only be specified during creation
 or the first time the subnet is updated into IPV4_IPV6 dual stack. If the ipv6_type is EXTERNAL then this subnet
@@ -661,7 +660,7 @@ func resourceComputeSubnetworkUpdate(d *schema.ResourceData, meta interface{}) e
 			return err
 		}
 	}
-	if d.HasChange("private_ipv6_google_access") || d.HasChange("stack_type") {
+	if d.HasChange("private_ipv6_google_access") || d.HasChange("stack_type") || d.HasChange("ipv6_access_type") {
 		obj := make(map[string]interface{})
 
 		getUrl, err := replaceVars(d, config, "{{ComputeBasePath}}projects/{{project}}/regions/{{region}}/subnetworks/{{name}}")
@@ -693,6 +692,12 @@ func resourceComputeSubnetworkUpdate(d *schema.ResourceData, meta interface{}) e
 		} else if v, ok := d.GetOkExists("stack_type"); !isEmptyValue(reflect.ValueOf(v)) && (ok || !reflect.DeepEqual(v, stackTypeProp)) {
 			obj["stackType"] = stackTypeProp
 		}
+		ipv6AccessTypeProp, err := expandComputeSubnetworkIpv6AccessType(d.Get("ipv6_access_type"), d, config)
+		if err != nil {
+			return err
+		} else if v, ok := d.GetOkExists("ipv6_access_type"); !isEmptyValue(reflect.ValueOf(v)) && (ok || !reflect.DeepEqual(v, ipv6AccessTypeProp)) {
+			obj["ipv6AccessType"] = ipv6AccessTypeProp
+		}
 
 		url, err := replaceVars(d, config, "{{ComputeBasePath}}projects/{{project}}/regions/{{region}}/subnetworks/{{name}}")
 		if err != nil {

google/resource_compute_subnetwork_test.go

@@ -331,6 +331,37 @@ func TestAccComputeSubnetwork_flowLogsMigrate(t *testing.T) {
 	})
 }
 
+func TestAccComputeSubnetwork_ipv6(t *testing.T) {
+	t.Parallel()
+
+	cnName := fmt.Sprintf("tf-test-%s", randString(t, 10))
+	subnetworkName := fmt.Sprintf("tf-test-%s", randString(t, 10))
+
+	vcrTest(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckComputeSubnetworkDestroyProducer(t),
+		Steps: []resource.TestStep{
+			{
+				Config: testAccComputeSubnetwork_ipv4(cnName, subnetworkName),
+			},
+			{
+				ResourceName:      "google_compute_subnetwork.subnetwork",
+				ImportState:       true,
+				ImportStateVerify: true,
+			},
+			{
+				Config: testAccComputeSubnetwork_ipv6(cnName, subnetworkName),
+			},
+			{
+				ResourceName:      "google_compute_subnetwork.subnetwork",
+				ImportState:       true,
+				ImportStateVerify: true,
+			},
+		},
+	})
+}
+
 func testAccCheckComputeSubnetworkExists(t *testing.T, n string, subnetwork *compute.Subnetwork) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
 		rs, ok := s.RootModule().Resources[n]
@@ -728,3 +759,37 @@ resource "google_compute_subnetwork" "network-with-flow-logs" {
 }
 `, cnName, subnetworkName)
 }
+
+func testAccComputeSubnetwork_ipv4(cnName, subnetworkName string) string {
+	return fmt.Sprintf(`
+resource "google_compute_network" "custom-test" {
+  name                    = "%s"
+  auto_create_subnetworks = false
+}
+
+resource "google_compute_subnetwork" "subnetwork" {
+  name          = "%s"
+  ip_cidr_range = "10.0.0.0/16"
+  region        = "us-central1"
+  network       = google_compute_network.custom-test.self_link
+}
+`, cnName, subnetworkName)
+}
+
+func testAccComputeSubnetwork_ipv6(cnName, subnetworkName string) string {
+	return fmt.Sprintf(`
+resource "google_compute_network" "custom-test" {
+  name                    = "%s"
+  auto_create_subnetworks = false
+}
+
+resource "google_compute_subnetwork" "subnetwork" {
+  name             = "%s"
+  ip_cidr_range    = "10.0.0.0/16"
+  region           = "us-central1"
+  network          = google_compute_network.custom-test.self_link
+  stack_type       = "IPV4_IPV6"
+  ipv6_access_type = "EXTERNAL"
+}
+`, cnName, subnetworkName)
+}