instead of changing existing method, add a new type

pkg/scheduler/framework/plugins/podtopologyspread/filtering_test.go

@@ -505,7 +505,7 @@ func TestPreFilterState(t *testing.T) {
 					{
 						MaxSkew:            3,
 						TopologyKey:        "node",
-						Selector:           labels.SelectorFromValidatedSet(labels.Set{"foo": "bar"}),
+						Selector:           mustConvertLabelSelectorAsSelector(t, st.MakeLabelSelector().Label("foo", "bar").Obj()),
 						MinDomains:         1,
 						NodeAffinityPolicy: v1.NodeInclusionPolicyHonor,
 						NodeTaintsPolicy:   v1.NodeInclusionPolicyIgnore,
@@ -513,7 +513,7 @@ func TestPreFilterState(t *testing.T) {
 					{
 						MaxSkew:            5,
 						TopologyKey:        "rack",
-						Selector:           labels.SelectorFromValidatedSet(labels.Set{"foo": "bar"}),
+						Selector:           mustConvertLabelSelectorAsSelector(t, st.MakeLabelSelector().Label("foo", "bar").Obj()),
 						MinDomains:         1,
 						NodeAffinityPolicy: v1.NodeInclusionPolicyHonor,
 						NodeTaintsPolicy:   v1.NodeInclusionPolicyIgnore,
@@ -1283,7 +1283,7 @@ func TestPreFilterState(t *testing.T) {
 					{
 						MaxSkew:            1,
 						TopologyKey:        "zone",
-						Selector:           labels.SelectorFromValidatedSet(labels.Set{"foo": "a"}),
+						Selector:           mustConvertLabelSelectorAsSelector(t, st.MakeLabelSelector().Label("foo", "a").Obj()),
 						MinDomains:         1,
 						NodeAffinityPolicy: v1.NodeInclusionPolicyHonor,
 						NodeTaintsPolicy:   v1.NodeInclusionPolicyIgnore,

staging/src/k8s.io/apimachinery/pkg/labels/labels.go

@@ -77,6 +77,8 @@ func (ls Set) AsValidatedSelector() (Selector, error) {
 // perform any validation.
 // According to our measurements this is significantly faster
 // in codepaths that matter at high scale.
+// Note: this method copies the Set; if the Set is immutable, consider wrapping it with SetSelector
+// instead, which does not copy.
 func (ls Set) AsSelectorPreValidated() Selector {
 	return SelectorFromValidatedSet(ls)
 }

staging/src/k8s.io/apimachinery/pkg/labels/selector.go

@@ -919,14 +919,6 @@ func SelectorFromSet(ls Set) Selector {
 	return SelectorFromValidatedSet(ls)
 }
 
-var (
-	// Create constants for hot-path selectors
-	value0Path, keyPath = func() (*field.Path, *field.Path) {
-		path := field.ToPath()
-		return path.Child("values").Index(0), path.Child("key")
-	}()
-)
-
 // ValidatedSelectorFromSet returns a Selector which will match exactly the given Set. A
 // nil and empty Sets are considered equivalent to Everything().
 // The Set is validated client-side, which allows to catch errors early.
@@ -934,29 +926,35 @@ func ValidatedSelectorFromSet(ls Set) (Selector, error) {
 	if ls == nil || len(ls) == 0 {
 		return internalSelector{}, nil
 	}
-
-	var allErrs field.ErrorList
-	for k, v := range ls {
-		if err := validateLabelKey(k, keyPath); err != nil {
-			allErrs = append(allErrs, err)
-		}
-		if err := validateLabelValue(k, v, value0Path); err != nil {
-			allErrs = append(allErrs, err)
+	requirements := make([]Requirement, 0, len(ls))
+	for label, value := range ls {
+		r, err := NewRequirement(label, selection.Equals, []string{value})
+		if err != nil {
+			return nil, err
 		}
+		requirements = append(requirements, *r)
 	}
-
-	// TODO: validate labels are valid label values
-	return setSelector(ls), allErrs.ToAggregate()
+	// sort to have deterministic string representation
+	sort.Sort(ByKey(requirements))
+	return internalSelector(requirements), nil
 }
 
 // SelectorFromValidatedSet returns a Selector which will match exactly the given Set.
 // A nil and empty Sets are considered equivalent to Everything().
 // It assumes that Set is already validated and doesn't do any validation.
+// Note: this method copies the Set; if the Set is immutable, consider wrapping it with SetSelector
+// instead, which does not copy.
 func SelectorFromValidatedSet(ls Set) Selector {
 	if ls == nil || len(ls) == 0 {
 		return internalSelector{}
 	}
-	return setSelector(ls)
+	requirements := make([]Requirement, 0, len(ls))
+	for label, value := range ls {
+		requirements = append(requirements, Requirement{key: label, operator: selection.Equals, strValues: []string{value}})
+	}
+	// sort to have deterministic string representation
+	sort.Sort(ByKey(requirements))
+	return internalSelector(requirements)
 }
 
 // ParseToRequirements takes a string representing a selector and returns a list of
@@ -968,9 +966,13 @@ func ParseToRequirements(selector string, opts ...field.PathOption) ([]Requireme
 	return parse(selector, field.ToPath(opts...))
 }
 
-type setSelector Set
+// SetSelector wraps a Set, allowing it to implement the Selector interface. Unlike
+// Set.AsSelectorPreValidated (which copies the input Set), this type simply wraps the underlying
+// Set. As a result, it is substantially more efficient, but requires the caller to not mutate the
+// Set.
+type SetSelector Set
 
-func (s setSelector) Matches(labels Labels) bool {
+func (s SetSelector) Matches(labels Labels) bool {
 	for k, v := range s {
 		if !labels.Has(k) || v != labels.Get(k) {
 			return false
@@ -979,11 +981,11 @@ func (s setSelector) Matches(labels Labels) bool {
 	return true
 }
 
-func (s setSelector) Empty() bool {
+func (s SetSelector) Empty() bool {
 	return len(s) == 0
 }
 
-func (s setSelector) String() string {
+func (s SetSelector) String() string {
 	keys := make([]string, 0, len(s))
 	for k := range s {
 		keys = append(keys, k)
@@ -1004,28 +1006,28 @@ func (s setSelector) String() string {
 	return b.String()
 }
 
-func (s setSelector) Add(r ...Requirement) Selector {
+func (s SetSelector) Add(r ...Requirement) Selector {
 	return s.toFullSelector().Add(r...)
 }
 
-func (s setSelector) Requirements() (requirements Requirements, selectable bool) {
+func (s SetSelector) Requirements() (requirements Requirements, selectable bool) {
 	return s.toFullSelector().Requirements()
 }
 
-func (s setSelector) DeepCopySelector() Selector {
-	res := make(setSelector, len(s))
+func (s SetSelector) DeepCopySelector() Selector {
+	res := make(SetSelector, len(s))
 	for k, v := range s {
 		res[k] = v
 	}
 	return res
 }
 
-func (s setSelector) RequiresExactMatch(label string) (value string, found bool) {
+func (s SetSelector) RequiresExactMatch(label string) (value string, found bool) {
 	v, f := s[label]
 	return v, f
 }
 
-func (s setSelector) toFullSelector() Selector {
+func (s SetSelector) toFullSelector() Selector {
 	if s == nil || len(s) == 0 {
 		return internalSelector{}
 	}
@@ -1038,4 +1040,4 @@ func (s setSelector) toFullSelector() Selector {
 	return internalSelector(requirements)
 }
 
-var _ Selector = setSelector{}
+var _ Selector = SetSelector{}

staging/src/k8s.io/apimachinery/pkg/labels/selector_test.go

@@ -826,6 +826,28 @@ func BenchmarkSelectorFromValidatedSet(b *testing.B) {
 	}
 }
 
+func BenchmarkSetSelector(b *testing.B) {
+	set := map[string]string{
+		"foo": "foo",
+		"bar": "bar",
+	}
+	matchee := Set(map[string]string{
+		"foo":   "foo",
+		"bar":   "bar",
+		"extra": "label",
+	})
+
+	for i := 0; i < b.N; i++ {
+		s := SetSelector(set)
+		if s.Empty() {
+			b.Errorf("Unexpected selector")
+		}
+		if !s.Matches(matchee) {
+			b.Errorf("Unexpected match")
+		}
+	}
+}
+
 func TestSetSelectorString(t *testing.T) {
 	cases := []struct {
 		set Set
@@ -847,7 +869,7 @@ func TestSetSelectorString(t *testing.T) {
 
 	for _, tt := range cases {
 		t.Run(tt.out, func(t *testing.T) {
-			if got := setSelector(tt.set).String(); tt.out != got {
+			if got := SetSelector(tt.set).String(); tt.out != got {
 				t.Fatalf("expected %v, got %v", tt.out, got)
 			}
 		})
@@ -936,13 +958,19 @@ func TestValidatedSelectorFromSet(t *testing.T) {
 	tests := []struct {
 		name             string
 		input            Set
-		expectedSelector Selector
+		expectedSelector internalSelector
 		expectedError    field.ErrorList
 	}{
 		{
-			name:             "Simple Set, no error",
-			input:            Set{"key": "val"},
-			expectedSelector: setSelector{"key": "val"},
+			name:  "Simple Set, no error",
+			input: Set{"key": "val"},
+			expectedSelector: internalSelector{
+				Requirement{
+					key:       "key",
+					operator:  selection.Equals,
+					strValues: []string{"val"},
+				},
+			},
 		},
 		{
 			name:  "Invalid Set, value too long",