Patchtransformers - drop copied code, improve deletion handling.

api/resource/resource.go

@@ -9,9 +9,11 @@ import (
 	"reflect"
 	"strings"
 
+	"sigs.k8s.io/kustomize/api/filters/patchstrategicmerge"
 	"sigs.k8s.io/kustomize/api/ifc"
 	"sigs.k8s.io/kustomize/api/resid"
 	"sigs.k8s.io/kustomize/api/types"
+	"sigs.k8s.io/kustomize/kyaml/filtersutil"
 	"sigs.k8s.io/yaml"
 )
 
@@ -396,6 +398,23 @@ func (r *Resource) AppendRefVarName(variable types.Var) {
 	r.refVarNames = append(r.refVarNames, variable.Name)
 }
 
+// ApplySmPatch applies the provided strategic merge patch.
+func (r *Resource) ApplySmPatch(patch *Resource) error {
+	node, err := filtersutil.GetRNode(patch)
+	if err != nil {
+		return err
+	}
+	n, ns := r.GetName(), r.GetNamespace()
+	err = filtersutil.ApplyToJSON(patchstrategicmerge.Filter{
+		Patch: node,
+	}, r)
+	if !r.IsEmpty() {
+		r.SetName(n)
+		r.SetNamespace(ns)
+	}
+	return err
+}
+
 // TODO: Add BinaryData once we sync to new k8s.io/api
 func mergeConfigmap(
 	mergedTo map[string]interface{},