limit scope of scratchDisks array by using bool, test formatting

google/resource_compute_instance.go

@@ -516,9 +516,9 @@ func resourceComputeInstanceCreate(d *schema.ResourceData, meta interface{}) err
 		disks = append(disks, bootDisk)
 	}
 
-	scratchDisks := []*compute.AttachedDisk{}
-	if _, ok := d.GetOk("scratch_disk"); ok {
-		scratchDisks, err = expandScratchDisks(d, config, zone)
+	var hasScratchDisk bool
+	if _, hasScratchDisk := d.GetOk("scratch_disk"); hasScratchDisk {
+		scratchDisks, err := expandScratchDisks(d, config, zone)
 		if err != nil {
 			return err
 		}
@@ -571,7 +571,7 @@ func resourceComputeInstanceCreate(d *schema.ResourceData, meta interface{}) err
 
 		if v, ok := d.GetOk(prefix + ".scratch"); ok {
 			if v.(bool) {
-				if len(scratchDisks) > 0 {
+				if hasScratchDisk {
 					return fmt.Errorf("Cannot set scratch disks using both `scratch_disk` and `disk` properties")
 				}
 				disk.Type = "SCRATCH"

google/resource_compute_instance_test.go

@@ -1431,30 +1431,31 @@ resource "google_compute_instance" "local-ssd" {
 
 func testAccComputeInstance_scratchDisk(instance string) string {
 	return fmt.Sprintf(`
-	resource "google_compute_instance" "scratch" {
-		name         = "%s"
-		machine_type = "n1-standard-1"
-		zone         = "us-central1-a"
-
-		boot_disk {
-			initialize_params {
-				image = "debian-8-jessie-v20160803"
-			}
-		}
+resource "google_compute_instance" "scratch" {
+	name         = "%s"
+	machine_type = "n1-standard-1"
+	zone         = "us-central1-a"
 
-		scratch_disk {
-			interface = "NVME"
+	boot_disk {
+		initialize_params {
+			image = "debian-8-jessie-v20160803"
 		}
+	}
 
-		scratch_disk {
-			interface = "SCSI"
-		}
+	scratch_disk {
+		interface = "NVME"
+	}
 
-		network_interface {
-			network = "default"
-		}
+	scratch_disk {
+		interface = "SCSI"
+	}
 
-	}`, instance)
+	network_interface {
+		network = "default"
+	}
+
+}
+`, instance)
 }
 
 func testAccComputeInstance_service_account(instance string) string {