Prepare removal of guest_accelerator ConfigModeAttr (#11425)

mmv1/third_party/terraform/services/compute/resource_compute_instance_test.go.erb

@@ -1741,6 +1741,20 @@ func TestAccComputeInstance_guestAcceleratorSkip(t *testing.T) {
 					testAccCheckComputeInstanceLacksGuestAccelerator(&instance),
 				),
 			},
+			// Recreate with guest_accelerator = []
+			{
+				Config: testAccComputeInstance_guestAcceleratorEmptyBlock(instanceName),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckComputeInstanceExists(t, "google_compute_instance.foobar", &instance),
+					testAccCheckComputeInstanceLacksGuestAccelerator(&instance),
+				),
+			},
+			// Check that count = 0 is the same as empty block []
+			{
+				Config:             testAccComputeInstance_guestAccelerator(instanceName, 0),
+				ExpectNonEmptyPlan: false,
+				PlanOnly:           true,
+			},
 		},
 	})
 
@@ -7098,6 +7112,38 @@ resource "google_compute_instance" "foobar" {
 `, instance, count)
 }
 
+func testAccComputeInstance_guestAcceleratorEmptyBlock(instance string) string {
+	return fmt.Sprintf(`
+data "google_compute_image" "my_image" {
+  family  = "debian-11"
+  project = "debian-cloud"
+}
+
+resource "google_compute_instance" "foobar" {
+  name         = "%s"
+  machine_type = "n1-standard-1"   // can't be e2 because of guest_accelerator
+  zone         = "us-east1-d"
+
+  boot_disk {
+    initialize_params {
+      image = data.google_compute_image.my_image.self_link
+    }
+  }
+
+  network_interface {
+    network = "default"
+  }
+
+  scheduling {
+    # Instances with guest accelerators do not support live migration.
+    on_host_maintenance = "TERMINATE"
+  }
+
+  guest_accelerator = []
+}
+`, instance)
+}
+
 func testAccComputeInstance_minCpuPlatform(instance string) string {
 	return fmt.Sprintf(`
 data "google_compute_image" "my_image" {

mmv1/third_party/terraform/services/container/resource_container_node_pool_test.go.erb

@@ -1322,6 +1322,12 @@ func TestAccContainerNodePool_012_ConfigModeAttr(t *testing.T) {
 				ImportState:             true,
 				ImportStateVerify:       true,
 			},
+			{
+				// Test guest_accelerator.count = 0 is the same as guest_accelerator = []
+				Config:             testAccContainerNodePool_EmptyGuestAccelerator(cluster, np, networkName, subnetworkName),
+				ExpectNonEmptyPlan: false,
+				PlanOnly:           true,
+			},
 		},
 	})
 }
@@ -3800,6 +3806,7 @@ resource "google_container_node_pool" "np" {
 
   node_config {
     guest_accelerator = []
+	machine_type = "n1-highmem-4"
   }
 }
 `, cluster, networkName, subnetworkName, np)

mmv1/third_party/terraform/website/docs/guides/version_6_upgrade.html.markdown

@@ -126,6 +126,20 @@ Removed in favor of field `settings.ip_configuration.ssl_mode`.
 
 An empty value means the setting should be cleared.
 
+## Resources: `google_container_cluster`, `google_container_node_pool`, and `google_compute_instance`
+
+### `guest_accelerator = []` is no longer valid configuration
+
+To explicitly set an empty list of objects, set `guest_accelerator.count = 0`.
+
+Previously, to explicitly set `guest_accelerator` as an empty list of objects, the specific configuration `guest_accelerator = []` was necessary.
+This was to maintain compatability in behavior between Terraform versions 0.11 and 0.12 using a special setting ["attributes as blocks"](https://developer.hashicorp.com/terraform/language/attr-as-blocks).
+This special setting causes other breakages so it is now removed, with setting `guest_accelerator.count = 0` available as an alternative form of empty `guest_accelerator` object.
+
+### `guest_accelerator.gpu_driver_installation_config = []` and `guest_accelerator.gpu_sharing_config = []` are no longer valid configuration
+
+These were never intended to be set this way. Removing the fields from configuration should not produce a diff.
+
 ## Resource: `google_domain`
 
 ### Domain deletion now prevented by default with `deletion_protection`