[Issue:#2] Fix for disk resize issue

This commit fixes the issue where a resize of disk would result
in deletion and creation of the disk. With this change if the
size of an existing disk is increased, terraform reconfigures
the vm's disk with the new size and does not delete create the
disk.

vsphere/resource_vsphere_virtual_machine.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"log"
 	"net"
+	"reflect"
 	"strconv"
 	"strings"
 
@@ -554,6 +555,67 @@ func resourceVSphereVirtualMachineUpdate(d *schema.ResourceData, meta interface{
 		addedDisks := newDiskSet.Difference(oldDiskSet)
 		removedDisks := oldDiskSet.Difference(newDiskSet)
 
+		log.Printf("[DEBUG] addedDisks : %#v\n", addedDisks)
+		log.Printf("[DEBUG] removedDisks : %#v\n", removedDisks)
+
+		modifiedDisks := make([]map[string]interface{}, 0)
+
+		for _, addedDiskRaw := range addedDisks.List() {
+			addedDisk, _ := addedDiskRaw.(map[string]interface{})
+			newSize := addedDisk["size"].(int)
+			ad := make(map[string]interface{})
+			for k, v := range addedDisk {
+				ad[k] = v
+			}
+			for _, removedDiskRaw := range removedDisks.List() {
+				removedDisk, _ := removedDiskRaw.(map[string]interface{})
+				rd := make(map[string]interface{})
+				for k, v := range removedDisk {
+					rd[k] = v
+				}
+				ad["uuid"], rd["uuid"] = "", ""
+				ad["key"], rd["key"] = 0, 0
+				ad["size"], rd["size"] = 0, 0
+				ok := reflect.DeepEqual(ad, rd)
+				if ok {
+					if removedDisk["size"].(int) < newSize {
+						log.Printf("[DEBUG] Mofifying the size to %d", newSize)
+						addedDisks.Remove(addedDisk)
+						removedDisks.Remove(removedDisk)
+						removedDisk["size"] = newSize
+						modifiedDisks = append(modifiedDisks, removedDisk)
+					}
+					break
+				}
+			}
+		}
+
+		log.Printf("[DEBUG] addedDisks after resize: %#v\n", addedDisks)
+		log.Printf("[DEBUG] removedDisks after resize: %#v\n", removedDisks)
+		log.Printf("[DEBUG] modifiedDisks after resize: %#v\n", modifiedDisks)
+
+		// Just Resized disks
+		for _, disk := range modifiedDisks {
+			log.Printf("[DEBUG] Modifying disk  : %#v\n", disk)
+			devices, err := vm.Device(context.TODO())
+			if err != nil {
+				return fmt.Errorf("[ERROR] Update resize Disk - Could not get virtual device list: %v", err)
+			}
+			v := devices.FindByKey(int32(disk["key"].(int)))
+			virtualDisk, _ := v.(*types.VirtualDisk)
+
+			newSize := disk["size"].(int)
+			virtualDisk.CapacityInKB = int64(newSize * 1024 * 1024)
+
+			config := &types.VirtualDeviceConfigSpec{
+				Device:    virtualDisk,
+				Operation: types.VirtualDeviceConfigSpecOperationEdit,
+			}
+			config.FileOperation = ""
+			configSpec.DeviceChange = append(configSpec.DeviceChange, config)
+
+		}
+
 		// Removed disks
 		for _, diskRaw := range removedDisks.List() {
 			if disk, ok := diskRaw.(map[string]interface{}); ok {