func migrateVSphereVirtualMachineStateV3(is *terraform.InstanceState, meta interface{}) error {
	// All we really preserve from the old state is the UUID of the virtual
	// machine. We leverage some of the special parts of the import functionality
	// - namely validating disks, and flagging the VM as imported in the state to
	// guard against someone adding customization to the configuration and
	// accidentally forcing a new resource.
	//
	// Read will handle most of the population post-migration as it does for
	// import, and there will be an unavoidable diff for TF-only options on the
	// next plan.
	client := meta.(*VSphereClient).vimClient
	id := is.ID

	log.Printf("[DEBUG] Migrate state for VM at UUID %q", id)
	vm, err := virtualmachine.FromUUID(client, id)
	if err != nil {
		return fmt.Errorf("error fetching virtual machine: %s", err)
	}
	props, err := virtualmachine.Properties(vm)
	if err != nil {
		return fmt.Errorf("error fetching virtual machine properties: %s", err)
	}

	// Populate the UUID field of all virtual disks in state.
	diskCnt, _ := strconv.Atoi(is.Attributes["disk.#"])
	l := object.VirtualDeviceList(props.Config.Hardware.Device)
	for i := 0; i < diskCnt; i++ {
		v, ok := is.Attributes[fmt.Sprintf("disk.%d.key", i)]
		if !ok {
			return fmt.Errorf("corrupt state: key disk.%d.key not found", i)
		}
		key, err := strconv.Atoi(v)
		if err != nil {
			return fmt.Errorf("corrupt state: strconv.Atoi error on disk.%d.key: %s", i, err)
		}
		if key < 1 {
			// This is a possibility during v1 -> v3 migrations, and would fail to
			// find a device anyway, so we just ignore these.
			continue
		}
		device := l.FindByKey(int32(key))
		if device == nil {
			// Missing device, pass
			continue
		}
		disk, ok := device.(*types.VirtualDisk)
		if !ok {
			// Not the device we are looking for
			continue
		}
		backing, ok := disk.Backing.(*types.VirtualDiskFlatVer2BackingInfo)
		if !ok {
			// Someone has tampered with the VM to the point where we really should
			// not mess with it. We can't account for all cases, but if someone has
			// added something like an RDM disk or something else that is not
			// VMDK-backed, we don't want to continue. We have never supported this.
			return fmt.Errorf("disk device %s is not a VMDK-backed virtual disk and state import cannot continue", l.Name(disk))
		}
		is.Attributes[fmt.Sprintf("disk.%d.uuid", i)] = backing.Uuid
	}

	d := resourceVSphereVirtualMachine().Data(&terraform.InstanceState{})
	log.Printf("[DEBUG] %s: Migration to V3 complete", resourceVSphereVirtualMachineIDString(d))
	return nil
}
func migrateVSphereVirtualMachineStateV3(is *terraform.InstanceState, meta interface{}) error {
	// All we really preserve from the old state is the UUID of the virtual
	// machine. We leverage some of the special parts of the import functionality
	// - namely validating disks, and flagging the VM as imported in the state to
	// guard against someone adding customization to the configuration and
	// accidentally forcing a new resource.
	//
	// Read will handle most of the population post-migration as it does for
	// import, and there will be an unavoidable diff for TF-only options on the
	// next plan.
	client := meta.(*VSphereClient).vimClient
	id := is.ID

	log.Printf("[DEBUG] Migrate state for VM at UUID %q", id)
	vm, err := virtualmachine.FromUUID(client, id)
	if err != nil {
		return fmt.Errorf("error fetching virtual machine: %s", err)
	}
	props, err := virtualmachine.Properties(vm)
	if err != nil {
		return fmt.Errorf("error fetching virtual machine properties: %s", err)
	}

	// Populate the UUID field of all virtual disks in state.
	diskCnt, _ := strconv.Atoi(is.Attributes["disk.#"])
	l := object.VirtualDeviceList(props.Config.Hardware.Device)
	for i := 0; i < diskCnt; i++ {
		v, ok := is.Attributes[fmt.Sprintf("disk.%d.key", i)]
		if !ok {
			return fmt.Errorf("corrupt state: key disk.%d.key not found", i)
		}
		key, err := strconv.Atoi(v)
		if err != nil {
			return fmt.Errorf("corrupt state: strconv.Atoi error on disk.%d.key: %s", i, err)
		}
		if key < 1 {
			// This is a possibility during v1 -> v3 migrations, and would fail to
			// find a device anyway, so we just ignore these.
			continue
		}
		device := l.FindByKey(int32(key))
		if device == nil {
			// Missing device, pass
			continue
		}
		disk, ok := device.(*types.VirtualDisk)
		if !ok {
			// Not the device we are looking for
			continue
		}
		backing, ok := disk.Backing.(*types.VirtualDiskFlatVer2BackingInfo)
		if !ok {
			// Someone has tampered with the VM to the point where we really should
			// not mess with it. We can't account for all cases, but if someone has
			// added something like an RDM disk or something else that is not
			// VMDK-backed, we don't want to continue. We have never supported this.
			return fmt.Errorf("disk device %s is not a VMDK-backed virtual disk and state import cannot continue", l.Name(disk))
		}
		is.Attributes[fmt.Sprintf("disk.%d.uuid", i)] = backing.Uuid
	}

	d := resourceVSphereVirtualMachine().Data(&terraform.InstanceState{})
	log.Printf("[DEBUG] %s: Migration to V3 complete", resourceVSphereVirtualMachineIDString(d))
	return nil
}
// migrateVSphereVirtualMachineStateV3 migrates the state of the
// vsphere_virtual_machine from version 2 to version 3.