Make the hash consistent again (hashicorp#11546)

The existing hash function for set items cannot generate consistent hashes when using both `Optional` and `Computed` on a schema field.

I tried to add this use case to the existing code base, but came to the conclusion this would be quite an endeavor.

That together with the fact this is the only field in all sets used in all builtin providers/resources that would be using both options at the same time, made me decide to change this single resource instead.

Author: Sander van Harmelen

builtin/providers/cloudstack/resource_cloudstack_port_forward.go

@@ -3,11 +3,10 @@ package cloudstack
 import (
 	"fmt"
 	"log"
-	"sync"
-	"time"
-
 	"strconv"
 	"strings"
+	"sync"
+	"time"
 
 	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/helper/schema"
@@ -68,7 +67,6 @@ func resourceCloudStackPortForward() *schema.Resource {
 						"vm_guest_ip": &schema.Schema{
 							Type:     schema.TypeString,
 							Optional: true,
-							Computed: true,
 						},
 
 						"uuid": &schema.Schema{
@@ -160,7 +158,7 @@ func createPortForward(d *schema.ResourceData, meta interface{}, forward map[str
 	p := cs.Firewall.NewCreatePortForwardingRuleParams(d.Id(), forward["private_port"].(int),
 		forward["protocol"].(string), forward["public_port"].(int), vm.Id)
 
-	if vmGuestIP, ok := forward["vm_guest_ip"]; ok {
+	if vmGuestIP, ok := forward["vm_guest_ip"]; ok && vmGuestIP.(string) != "" {
 		p.SetVmguestip(vmGuestIP.(string))
 
 		// Set the network ID based on the guest IP, needed when the public IP address
@@ -273,7 +271,13 @@ func resourceCloudStackPortForwardRead(d *schema.ResourceData, meta interface{})
 			forward["private_port"] = privPort
 			forward["public_port"] = pubPort
 			forward["virtual_machine_id"] = f.Virtualmachineid
-			forward["vm_guest_ip"] = f.Vmguestip
+
+			// This one is a bit tricky. We only want to update this optional value
+			// if we've set one ourselves. If not this would become a computed value
+			// and that would mess up the calculated hash of the set item.
+			if forward["vm_guest_ip"].(string) != "" {
+				forward["vm_guest_ip"] = f.Vmguestip
+			}
 
 			forwards.Add(forward)
 		}