Add builtin label transformer.

plugin/builtin/labeltransformer/LabelTransformer.go

@@ -0,0 +1,39 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+//go:generate go run sigs.k8s.io/kustomize/plugin/pluginator
+package main
+
+import (
+	"sigs.k8s.io/kustomize/pkg/ifc"
+	"sigs.k8s.io/kustomize/pkg/resmap"
+	"sigs.k8s.io/kustomize/pkg/transformers"
+	"sigs.k8s.io/kustomize/pkg/transformers/config"
+	"sigs.k8s.io/yaml"
+)
+
+// Add the given labels to the given field specifications.
+type plugin struct {
+	Labels     map[string]string  `json:"labels,omitempty" yaml:"labels,omitempty"`
+	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
+}
+
+var KustomizePlugin plugin
+
+func (p *plugin) Config(
+	ldr ifc.Loader, rf *resmap.Factory, c []byte) (err error) {
+	p.Labels = nil
+	p.FieldSpecs = nil
+	return yaml.Unmarshal(c, p)
+}
+
+func (p *plugin) Transform(m resmap.ResMap) error {
+	t, err := transformers.NewMapTransformer(
+		p.FieldSpecs,
+		p.Labels,
+	)
+	if err != nil {
+		return err
+	}
+	return t.Transform(m)
+}