From 133a40d77f437399aada30702ce06158b8f0c3cd Mon Sep 17 00:00:00 2001
From: Sander van Harmelen <sander@xanzy.io>
Date: Thu, 15 Jan 2015 15:33:52 +0100
Subject: [PATCH] Sets should init only once...
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Currently the `sync.Once` call is only used to init a Set in the add()
func. So when you add a value to a Set that is the result of one of the
Set operations (i.e. union, difference, intersect) the Set will be
reinitialised and the exiting values will be lost.

I don’t have a clue why this is showing up in my ACC tests just now, as
this code is in there for quite some time already. Somehow it seems to
have something to do with the refactoring of the helper/schema done
last week, as I cannot reproduce this with
47f02f80bca83ebde01959be840de800fc639a04
---
 helper/schema/set.go      |  6 +++---
 helper/schema/set_test.go | 21 +++++++++++++++------
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/helper/schema/set.go b/helper/schema/set.go
index 689be4f9f..78c68bdb7 100644
--- a/helper/schema/set.go
+++ b/helper/schema/set.go
@@ -59,7 +59,7 @@ func (s *Set) List() []interface{} {
 // a new third set that has only the elements unique to this set.
 func (s *Set) Difference(other *Set) *Set {
 	result := &Set{F: s.F}
-	result.init()
+	result.once.Do(result.init)
 
 	for k, v := range s.m {
 		if _, ok := other.m[k]; !ok {
@@ -74,7 +74,7 @@ func (s *Set) Difference(other *Set) *Set {
 // and returns a new third set.
 func (s *Set) Intersection(other *Set) *Set {
 	result := &Set{F: s.F}
-	result.init()
+	result.once.Do(result.init)
 
 	for k, v := range s.m {
 		if _, ok := other.m[k]; ok {
@@ -89,7 +89,7 @@ func (s *Set) Intersection(other *Set) *Set {
 // set.
 func (s *Set) Union(other *Set) *Set {
 	result := &Set{F: s.F}
-	result.init()
+	result.once.Do(result.init)
 
 	for k, v := range s.m {
 		result.m[k] = v
diff --git a/helper/schema/set_test.go b/helper/schema/set_test.go
index 7c9caa96e..8ae4be479 100644
--- a/helper/schema/set_test.go
+++ b/helper/schema/set_test.go
@@ -40,8 +40,11 @@ func TestSetDifference(t *testing.T) {
 	s2.Add(5)
 	s2.Add(25)
 
-	expected := []interface{}{1}
-	actual := s1.Difference(s2).List()
+	difference := s1.Difference(s2)
+	difference.Add(2)
+
+	expected := []interface{}{1, 2}
+	actual := difference.List()
 	if !reflect.DeepEqual(actual, expected) {
 		t.Fatalf("bad: %#v", actual)
 	}
@@ -57,8 +60,11 @@ func TestSetIntersection(t *testing.T) {
 	s2.Add(5)
 	s2.Add(25)
 
-	expected := []interface{}{5}
-	actual := s1.Intersection(s2).List()
+	intersection := s1.Intersection(s2)
+	intersection.Add(2)
+
+	expected := []interface{}{2, 5}
+	actual := intersection.List()
 	if !reflect.DeepEqual(actual, expected) {
 		t.Fatalf("bad: %#v", actual)
 	}
@@ -74,8 +80,11 @@ func TestSetUnion(t *testing.T) {
 	s2.Add(5)
 	s2.Add(25)
 
-	expected := []interface{}{1, 5, 25}
-	actual := s1.Union(s2).List()
+	union := s1.Union(s2)
+	union.Add(2)
+
+	expected := []interface{}{1, 2, 5, 25}
+	actual := union.List()
 	if !reflect.DeepEqual(actual, expected) {
 		t.Fatalf("bad: %#v", actual)
 	}