Refactor the PrefixSuffixTransformer into separate prefix- and suffix transformers (#4318)

* Refactor prefix filter into its own filter, decoupled from the prefixsuffix filter

* Refactor prefix transformer into its own transformer, decoupled from the prefixsuffix transformer

* Refactor suffix filter into its own filter, decoupled from the prefixsuffix filter

* Refactor suffix transformer into its own transformer, decoupled from the prefixsuffix transformer

* Add a default nameSuffix field spec in addition to the namePrefix

* Remove the PrefixSuffixTransformer from the list of builtin transformers

* Add a multi-transformer to builtinhelpers.TransformFactories

* Remove the implementation of the prefixsuffixtransformer.PrefixSuffixTransformer

* Resolve style and format related feedback from the pull request

* Add test to test the legacy PrefixSuffixTransformer for BC purposes

api/filters/suffix/doc.go

@@ -0,0 +1,6 @@
+// Copyright 2021 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package suffix contains a kio.Filter implementation of the kustomize
+// SuffixTransformer.
+package suffix

api/filters/suffix/example_test.go

@@ -0,0 +1,47 @@
+// Copyright 2021 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package suffix_test
+
+import (
+	"bytes"
+	"log"
+	"os"
+
+	"sigs.k8s.io/kustomize/api/filters/suffix"
+	"sigs.k8s.io/kustomize/api/types"
+	"sigs.k8s.io/kustomize/kyaml/kio"
+)
+
+func ExampleFilter() {
+	err := kio.Pipeline{
+		Inputs: []kio.Reader{&kio.ByteReader{Reader: bytes.NewBufferString(`
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+---
+apiVersion: example.com/v1
+kind: Bar
+metadata:
+  name: instance
+`)}},
+		Filters: []kio.Filter{suffix.Filter{
+			Suffix: "-baz", FieldSpec: types.FieldSpec{Path: "metadata/name"}}},
+		Outputs: []kio.Writer{kio.ByteWriter{Writer: os.Stdout}},
+	}.Execute()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Output:
+	// apiVersion: example.com/v1
+	// kind: Foo
+	// metadata:
+	//   name: instance-baz
+	// ---
+	// apiVersion: example.com/v1
+	// kind: Bar
+	// metadata:
+	//   name: instance-baz
+}

api/filters/suffix/suffix.go

@@ -0,0 +1,42 @@
+// Copyright 2021 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package suffix
+
+import (
+	"fmt"
+
+	"sigs.k8s.io/kustomize/api/filters/fieldspec"
+	"sigs.k8s.io/kustomize/api/filters/filtersutil"
+	"sigs.k8s.io/kustomize/api/types"
+	"sigs.k8s.io/kustomize/kyaml/kio"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
+
+// Filter applies resource name suffix's using the fieldSpecs
+type Filter struct {
+	Suffix string `json:"suffix,omitempty" yaml:"suffix,omitempty"`
+
+	FieldSpec types.FieldSpec `json:"fieldSpec,omitempty" yaml:"fieldSpec,omitempty"`
+}
+
+var _ kio.Filter = Filter{}
+
+func (f Filter) Filter(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
+	return kio.FilterAll(yaml.FilterFunc(f.run)).Filter(nodes)
+}
+
+func (f Filter) run(node *yaml.RNode) (*yaml.RNode, error) {
+	err := node.PipeE(fieldspec.Filter{
+		FieldSpec:  f.FieldSpec,
+		SetValue:   f.evaluateField,
+		CreateKind: yaml.ScalarNode, // Name is a ScalarNode
+		CreateTag:  yaml.NodeTagString,
+	})
+	return node, err
+}
+
+func (f Filter) evaluateField(node *yaml.RNode) error {
+	return filtersutil.SetScalar(fmt.Sprintf(
+		"%s%s", node.YNode().Value, f.Suffix))(node)
+}

api/filters/suffix/suffix_test.go

@@ -0,0 +1,106 @@
+// Copyright 2021 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package suffix_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"sigs.k8s.io/kustomize/api/filters/suffix"
+	filtertest_test "sigs.k8s.io/kustomize/api/testutils/filtertest"
+	"sigs.k8s.io/kustomize/api/types"
+)
+
+var tests = map[string]TestCase{
+	"suffix": {
+		input: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+---
+apiVersion: example.com/v1
+kind: Bar
+metadata:
+  name: instance
+`,
+		expected: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance-foo
+---
+apiVersion: example.com/v1
+kind: Bar
+metadata:
+  name: instance-foo
+`,
+		filter: suffix.Filter{
+			Suffix:    "-foo",
+			FieldSpec: types.FieldSpec{Path: "metadata/name"},
+		},
+	},
+
+	"data-fieldspecs": {
+		input: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+a:
+  b:
+    c: d
+---
+apiVersion: example.com/v1
+kind: Bar
+metadata:
+  name: instance
+a:
+  b:
+    c: d
+`,
+		expected: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+a:
+  b:
+    c: d-foo
+---
+apiVersion: example.com/v1
+kind: Bar
+metadata:
+  name: instance
+a:
+  b:
+    c: d-foo
+`,
+		filter: suffix.Filter{
+			Suffix:    "-foo",
+			FieldSpec: types.FieldSpec{Path: "a/b/c"},
+		},
+	},
+}
+
+type TestCase struct {
+	input    string
+	expected string
+	filter   suffix.Filter
+}
+
+func TestFilter(t *testing.T) {
+	for name := range tests {
+		test := tests[name]
+		t.Run(name, func(t *testing.T) {
+			if !assert.Equal(t,
+				strings.TrimSpace(test.expected),
+				strings.TrimSpace(
+					filtertest_test.RunFilter(t, test.input, test.filter))) {
+				t.FailNow()
+			}
+		})
+	}
+}