simplify code flow: skip the step if no run_volume_tags provided

builder/amazon/ebs/step_tag_ebs_volumes.go

@@ -18,34 +18,35 @@ func (s *stepTagEBSVolumes) Run(state multistep.StateBag) multistep.StepAction {
 	instance := state.Get("instance").(*ec2.Instance)
 	ui := state.Get("ui").(packer.Ui)
 
-	if len(s.VolumeRunTags) > 0 {
+	if len(s.VolumeRunTags) == 0 {
+		return multistep.ActionContinue
+	}
 
-		volumeIds := make([]*string, 0)
-		for _, v := range instance.BlockDeviceMappings {
-			if ebs := v.Ebs; ebs != nil {
-				volumeIds = append(volumeIds, ebs.VolumeId)
-			}
+	volumeIds := make([]*string, 0)
+	for _, v := range instance.BlockDeviceMappings {
+		if ebs := v.Ebs; ebs != nil {
+			volumeIds = append(volumeIds, ebs.VolumeId)
 		}
+	}
 
-		if len(volumeIds) == 0 {
-			return multistep.ActionContinue
-		}
+	if len(volumeIds) == 0 {
+		return multistep.ActionContinue
+	}
 
-		ui.Say(fmt.Sprintf("Adding tags to source EBS Volumes:"))
-		tags := common.ConvertToEC2Tags(s.VolumeRunTags, ui)
-
-		_, err := ec2conn.CreateTags(&ec2.CreateTagsInput{
-			Resources: []*string{
-				instance.BlockDeviceMappings[0].Ebs.VolumeId,
-			},
-			Tags: tags,
-		})
-		if err != nil {
-			err := fmt.Errorf("Error tagging source EBS Volumes on %s: %s", *instance.InstanceId, err)
-			state.Put("error", err)
-			ui.Error(err.Error())
-			return multistep.ActionHalt
-		}
+	ui.Say(fmt.Sprintf("Adding tags to source EBS Volumes:"))
+	tags := common.ConvertToEC2Tags(s.VolumeRunTags, ui)
+
+	_, err := ec2conn.CreateTags(&ec2.CreateTagsInput{
+		Resources: []*string{
+			instance.BlockDeviceMappings[0].Ebs.VolumeId,
+		},
+		Tags: tags,
+	})
+	if err != nil {
+		err := fmt.Errorf("Error tagging source EBS Volumes on %s: %s", *instance.InstanceId, err)
+		state.Put("error", err)
+		ui.Error(err.Error())
+		return multistep.ActionHalt
 	}
 
 	return multistep.ActionContinue