From f98bc7d45435d0a48a48178ebe439296c554fb4c Mon Sep 17 00:00:00 2001
From: allencloud <allen.sun@daocloud.io>
Date: Fri, 23 Jun 2017 11:41:18 +0800
Subject: [PATCH] fix CopyStrings and ShuffleStrings for slice when slice is
 nil

Signed-off-by: allencloud <allen.sun@daocloud.io>
---
 pkg/util/slice/slice.go      |  6 ++++++
 pkg/util/slice/slice_test.go | 35 ++++++++++++++++++++++++++++-------
 2 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/pkg/util/slice/slice.go b/pkg/util/slice/slice.go
index 1b8f67c0c1..205b597c40 100644
--- a/pkg/util/slice/slice.go
+++ b/pkg/util/slice/slice.go
@@ -26,6 +26,9 @@ import (
 // CopyStrings copies the contents of the specified string slice
 // into a new slice.
 func CopyStrings(s []string) []string {
+	if s == nil {
+		return nil
+	}
 	c := make([]string, len(s))
 	copy(c, s)
 	return c
@@ -41,6 +44,9 @@ func SortStrings(s []string) []string {
 // ShuffleStrings copies strings from the specified slice into a copy in random
 // order. It returns a new slice.
 func ShuffleStrings(s []string) []string {
+	if s == nil {
+		return nil
+	}
 	shuffled := make([]string, len(s))
 	perm := utilrand.Perm(len(s))
 	for i, j := range perm {
diff --git a/pkg/util/slice/slice_test.go b/pkg/util/slice/slice_test.go
index 7d74437df1..1c02f42041 100644
--- a/pkg/util/slice/slice_test.go
+++ b/pkg/util/slice/slice_test.go
@@ -22,15 +22,29 @@ import (
 )
 
 func TestCopyStrings(t *testing.T) {
-	src := []string{"a", "c", "b"}
-	dest := CopyStrings(src)
+	var src1 []string
+	dest1 := CopyStrings(src1)
 
-	if !reflect.DeepEqual(src, dest) {
-		t.Errorf("%v and %v are not equal", src, dest)
+	if !reflect.DeepEqual(src1, dest1) {
+		t.Errorf("%v and %v are not equal", src1, dest1)
 	}
 
-	src[0] = "A"
-	if reflect.DeepEqual(src, dest) {
+	src2 := []string{}
+	dest2 := CopyStrings(src2)
+
+	if !reflect.DeepEqual(src2, dest2) {
+		t.Errorf("%v and %v are not equal", src2, dest2)
+	}
+
+	src3 := []string{"a", "c", "b"}
+	dest3 := CopyStrings(src3)
+
+	if !reflect.DeepEqual(src3, dest3) {
+		t.Errorf("%v and %v are not equal", src3, dest3)
+	}
+
+	src3[0] = "A"
+	if reflect.DeepEqual(src3, dest3) {
 		t.Errorf("CopyStrings didn't make a copy")
 	}
 }
@@ -50,9 +64,16 @@ func TestSortStrings(t *testing.T) {
 }
 
 func TestShuffleStrings(t *testing.T) {
-	src := []string{"a", "b", "c", "d", "e", "f"}
+	var src []string
 	dest := ShuffleStrings(src)
 
+	if dest != nil {
+		t.Errorf("ShuffleStrings for a nil slice got a non-nil slice")
+	}
+
+	src = []string{"a", "b", "c", "d", "e", "f"}
+	dest = ShuffleStrings(src)
+
 	if len(src) != len(dest) {
 		t.Errorf("Shuffled slice is wrong length, expected %v got %v", len(src), len(dest))
 	}