Move some code to make it reusable without import cycles.

api/filters/annotations/annotations.go

@@ -24,7 +24,7 @@ type Filter struct {
 var _ kio.Filter = Filter{}
 
 func (f Filter) Filter(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
-	keys := filtersutil.SortedMapKeys(f.Annotations)
+	keys := yaml.SortedMapKeys(f.Annotations)
 	_, err := kio.FilterAll(yaml.FilterFunc(
 		func(node *yaml.RNode) (*yaml.RNode, error) {
 			for _, k := range keys {

api/filters/filtersutil/filtersutil.go

@@ -1,21 +0,0 @@
-// Copyright 2019 The Kubernetes Authors.
-// SPDX-License-Identifier: Apache-2.0
-
-package filtersutil
-
-import (
-	"sort"
-)
-
-// SortedMapKeys returns a sorted slice of keys to the given map.
-// Writing this function never gets old.
-func SortedMapKeys(m map[string]string) []string {
-	keys := make([]string, len(m))
-	i := 0
-	for k := range m {
-		keys[i] = k
-		i++
-	}
-	sort.Strings(keys)
-	return keys
-}

api/filters/filtersutil/filtersutil_test.go

@@ -1,34 +0,0 @@
-package filtersutil_test
-
-import (
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-	"sigs.k8s.io/kustomize/api/filters/filtersutil"
-)
-
-func TestSortedKeys(t *testing.T) {
-	testCases := map[string]struct {
-		input    map[string]string
-		expected []string
-	}{
-		"empty": {
-			input:    map[string]string{},
-			expected: []string{}},
-		"one": {
-			input:    map[string]string{"a": "aaa"},
-			expected: []string{"a"}},
-		"three": {
-			input:    map[string]string{"c": "ccc", "b": "bbb", "a": "aaa"},
-			expected: []string{"a", "b", "c"}},
-	}
-	for tn, tc := range testCases {
-		t.Run(tn, func(t *testing.T) {
-			if !assert.Equal(t,
-				filtersutil.SortedMapKeys(tc.input),
-				tc.expected) {
-				t.FailNow()
-			}
-		})
-	}
-}

api/filters/labels/labels.go

@@ -25,7 +25,7 @@ type Filter struct {
 var _ kio.Filter = Filter{}
 
 func (f Filter) Filter(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
-	keys := filtersutil.SortedMapKeys(f.Labels)
+	keys := yaml.SortedMapKeys(f.Labels)
 	_, err := kio.FilterAll(yaml.FilterFunc(
 		func(node *yaml.RNode) (*yaml.RNode, error) {
 			for _, k := range keys {