From b5f3aa68ae0a08a655c397f575892a921e1f127e Mon Sep 17 00:00:00 2001
From: Matthias Radestock <matthias.radestock@gmail.com>
Date: Mon, 3 Jul 2017 00:32:35 +0100
Subject: [PATCH] refactor: optimise "empty" case in report set constructors

---
 report/id_list.go  | 6 ++++++
 report/node_set.go | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/report/id_list.go b/report/id_list.go
index b285d5dbf..d75df56c3 100644
--- a/report/id_list.go
+++ b/report/id_list.go
@@ -7,11 +7,17 @@ var emptyIDList = IDList(MakeStringSet())
 
 // MakeIDList makes a new IDList.
 func MakeIDList(ids ...string) IDList {
+	if len(ids) == 0 {
+		return emptyIDList
+	}
 	return IDList(MakeStringSet(ids...))
 }
 
 // Add is the only correct way to add ids to an IDList.
 func (a IDList) Add(ids ...string) IDList {
+	if len(ids) == 0 {
+		return a
+	}
 	return IDList(StringSet(a).Add(ids...))
 }
 
diff --git a/report/node_set.go b/report/node_set.go
index 1baf2152c..3c4ba7141 100644
--- a/report/node_set.go
+++ b/report/node_set.go
@@ -27,6 +27,9 @@ func MakeNodeSet(nodes ...Node) NodeSet {
 // Add adds the nodes to the NodeSet. Add is the only valid way to grow a
 // NodeSet. Add returns the NodeSet to enable chaining.
 func (n NodeSet) Add(nodes ...Node) NodeSet {
+	if len(nodes) == 0 {
+		return n
+	}
 	result := n.psMap
 	if result == nil {
 		result = ps.NewMap()