Make selector parsing deterministic

pkg/labels/selector.go

@@ -18,6 +18,7 @@ package labels
 
 import (
 	"fmt"
+	"sort"
 	"strings"
 )
 
@@ -101,6 +102,7 @@ func SelectorFromSet(ls Set) Selector {
 // Takes a string repsenting a selector and returns an object suitable for matching, or an error.
 func ParseSelector(selector string) (Selector, error) {
 	parts := strings.Split(selector, ",")
+	sort.StringSlice(parts).Sort()
 	var items []Selector
 	for _, part := range parts {
 		if part == "" {

pkg/labels/selector_test.go

@@ -47,6 +47,17 @@ func TestSelectorParse(t *testing.T) {
 	}
 }
 
+func TestDeterministicParse(t *testing.T) {
+	s1, err := ParseSelector("x=a,a=x")
+	s2, err2 := ParseSelector("a=x,x=a")
+	if err != nil || err2 != nil {
+		t.Errorf("Unexpected parse error")
+	}
+	if s1.String() != s2.String() {
+		t.Errorf("Non-deterministic parse")
+	}
+}
+
 func expectMatch(t *testing.T, selector string, ls Set) {
 	lq, err := ParseSelector(selector)
 	if err != nil {