Implement replica transformer as patch alternative

plugin/builtin/ReplicaCountTransformer.go

@@ -0,0 +1,57 @@
+// Code generated by pluginator on ReplicaCountTransformer; DO NOT EDIT.
+package builtin
+
+import (
+	"github.com/pkg/errors"
+	"sigs.k8s.io/kustomize/pkg/ifc"
+	"sigs.k8s.io/kustomize/pkg/replica"
+	"sigs.k8s.io/kustomize/pkg/resid"
+	"sigs.k8s.io/kustomize/pkg/resmap"
+	"sigs.k8s.io/kustomize/pkg/transformers/config"
+	"sigs.k8s.io/yaml"
+)
+
+// Find matching replicas declarations and replace
+// the count.
+type ReplicaCountTransformerPlugin struct {
+	Replica    replica.Replica    `json:"replica,omitempty" yaml:"replica,omitempty"`
+	FieldSpecs []config.FieldSpec `json:"fieldSpecs,omitempty" yaml:"fieldSpecs,omitempty"`
+}
+
+func NewReplicaCountTransformerPlugin() *ReplicaCountTransformerPlugin {
+	return &ReplicaCountTransformerPlugin{}
+}
+
+func (p *ReplicaCountTransformerPlugin) Config(
+	ldr ifc.Loader, rf *resmap.Factory, c []byte) (err error) {
+
+	p.Replica = replica.Replica{}
+	p.FieldSpecs = nil
+	return yaml.Unmarshal(c, p)
+}
+
+func (p *ReplicaCountTransformerPlugin) Transform(m resmap.ResMap) error {
+	matcher := func(r resid.ResId) bool {
+		return r.ItemId.Name == p.Replica.Name
+	}
+
+	for _, r := range m.GetMatchingIds(matcher) {
+		kMap := m[r].Kunstructured.Map()
+
+		specInterface, ok := kMap["spec"]
+		if !ok {
+			return errors.New("'spec' not specified, replicas cannot be modified")
+		}
+
+		if spec, ok := specInterface.(map[string]interface{}); ok {
+			spec["replicas"] = p.Replica.Count
+			kMap["spec"] = spec
+		} else {
+			return errors.New("'spec' not structured as expected")
+		}
+
+		m[r].Kunstructured.SetMap(kMap)
+	}
+
+	return nil
+}