populate external_ipv6

.changelog/6244.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+compute: fixed missing `network_interface.0.ipv6_access_config.0.external_ipv6` output on `google_compute_instance`
+```

google/compute_instance_helpers.go

@@ -175,6 +175,7 @@ func flattenIpv6AccessConfigs(ipv6AccessConfigs []*compute.AccessConfig) []map[s
 			"network_tier": ac.NetworkTier,
 		}
 		flattened[i]["public_ptr_domain_name"] = ac.PublicPtrDomainName
+		flattened[i]["external_ipv6"] = ac.ExternalIpv6
 	}
 	return flattened
 }

google/resource_compute_instance_test.go

@@ -263,6 +263,7 @@ func TestAccComputeInstance_IPv6(t *testing.T) {
 				Check: resource.ComposeTestCheckFunc(
 					testAccCheckComputeInstanceExists(
 						t, "google_compute_instance.foobar", &instance),
+					testAccCheckComputeInstanceIpv6AccessConfigHasExternalIPv6(&instance),
 				),
 			},
 			{
@@ -2514,6 +2515,20 @@ func testAccCheckComputeInstanceAccessConfigHasNatIP(instance *compute.Instance)
 	}
 }
 
+func testAccCheckComputeInstanceIpv6AccessConfigHasExternalIPv6(instance *compute.Instance) resource.TestCheckFunc {
+	return func(s *terraform.State) error {
+		for _, i := range instance.NetworkInterfaces {
+			for _, c := range i.Ipv6AccessConfigs {
+				if c.ExternalIpv6 == "" {
+					return fmt.Errorf("no External IPv6")
+				}
+			}
+		}
+
+		return nil
+	}
+}
+
 func testAccCheckComputeInstanceAccessConfigHasPTR(instance *compute.Instance) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
 		for _, i := range instance.NetworkInterfaces {