refactor: use JoinHostPort for vnc tcp dialing (#541)

Replace manual `"%s:%d"` address formatting with `net.JoinHostPort` when dialing VNC. This ensures host/port strings are constructed correctly (including IPv6 hosts) and avoids malformed TCP target addresses.

Write VMX entries directly into the output buffer instead of formatting an intermediate string first. This avoids unnecessary allocations while preserving the same encoded output.

Signed-off-by: Ryan Johnson <ryan@tenthirtyam.org>

Author: tenthirtyam

builder/vmware/common/step_vnc_connect.go

@@ -46,7 +46,7 @@ func (s *StepVNCConnect) ConnectVNC(ctx context.Context, state multistep.StateBa
 	vncPort := state.Get("vnc_port").(int)
 	vncPassword := state.Get("vnc_password")
 
-	nc, err := net.Dial("tcp", fmt.Sprintf("%s:%d", vncIp, vncPort))
+	nc, err := net.Dial("tcp", net.JoinHostPort(vncIp, fmt.Sprintf("%d", vncPort)))
 	if err != nil {
 		err := fmt.Errorf("error connecting to VNC: %s", err)
 		state.Put("error", err)

builder/vmware/common/vmx.go

@@ -73,7 +73,7 @@ func EncodeVMX(contents map[string]string) string {
 		for _, c := range caseSensitive {
 			key = strings.Replace(key, strings.ToLower(c), c, 1)
 		}
-		buf.WriteString(fmt.Sprintf(pat, key, contents[k]))
+		fmt.Fprintf(&buf, pat, key, contents[k])
 	}
 
 	return buf.String()