✨ Added the no-op function that just injects its content

Setting the config.kubernetes.io/inject-config annotation will  add the
functionConfig to the set or resources with the
config.kubernetes.io/local-config annotation.

This is meant to inject whatever resource we want for replacement
instead of relying on flat configmaps.

main.go

@@ -13,7 +13,6 @@ import (
 	"sigs.k8s.io/kustomize/kyaml/fn/framework"
 	"sigs.k8s.io/kustomize/kyaml/fn/framework/command"
 	"sigs.k8s.io/kustomize/kyaml/kio/filters"
-	"sigs.k8s.io/kustomize/kyaml/kio/kioutil"
 	"sigs.k8s.io/kustomize/kyaml/resid"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
 )
@@ -28,7 +27,20 @@ func main() {
 
 		plugin, err := plugins.MakeBuiltinPlugin(resid.GvkFromNode(config))
 		if err != nil {
-			return errors.WrapPrefixf(err, "creating plugin")
+			// Check if config asks us to inject it
+			if _, ok := config.GetAnnotations()[utils.FunctionAnnotationInjectLocal]; ok {
+				injected := config.Copy()
+
+				err := utils.MakeResourceLocal(injected)
+				if err != nil {
+					return errors.WrapPrefixf(
+						err, "Error while mangling annotations on %s fails configuration", res.OrgId())
+				}
+				rl.Items = append(rl.Items, injected)
+				return nil
+			} else {
+				return errors.WrapPrefixf(err, "creating plugin")
+			}
 		}
 
 		yamlNode := config.YNode()
@@ -68,7 +80,7 @@ func main() {
 			// As it always add a filename by default, the local resources keep saved.
 			// To avoid this, an annotation `config.kubernetes.io/prune-local` present in a
 			// transformer makes all the local resources disappear.
-			if _, ok := config.GetAnnotations()["config.kubernetes.io/prune-local"]; ok {
+			if _, ok := config.GetAnnotations()[utils.FunctionAnnotationPruneLocal]; ok {
 				filter := &filters.IsLocalConfig{IncludeLocalConfig: false, ExcludeNonLocalConfig: false}
 				err = rl.Filter(filter)
 				if err != nil {
@@ -95,9 +107,7 @@ func main() {
 				// do that on functions. So we have added a special annotation
 				// `config.kubernetes.io/prune-local` to add on the last transformer.
 				// We set the filename of the generated resource in case it is forgotten.
-				r.Pipe(yaml.SetAnnotation(filters.LocalConfigAnnotation, "true"))
-				r.Pipe(yaml.SetAnnotation(kioutil.PathAnnotation, ".generated.yaml"))
-				r.Pipe(yaml.SetAnnotation(kioutil.LegacyPathAnnotation, ".generated.yaml"))
+				utils.MakeResourceLocal(&r.RNode)
 			}
 
 			rl.Items = append(rl.Items, rm.ToRNodeSlice()...)

pkg/utils/constants.go

@@ -12,4 +12,21 @@ const (
 	BuildAnnotationsRefBy             = konfig.ConfigAnnoDomain + "/refBy"
 	BuildAnnotationsGenBehavior       = konfig.ConfigAnnoDomain + "/generatorBehavior"
 	BuildAnnotationsGenAddHashSuffix  = konfig.ConfigAnnoDomain + "/needsHashSuffix"
+
+	// ConfigurationAnnotationDomain is the domain of function configuration
+	// annotations
+	ConfigurationAnnotationDomain = "config.kubernetes.io"
+
+	// Function configuration annotation
+	FunctionAnnotationFunction = ConfigurationAnnotationDomain + "/function"
+
+	// true when the resource is part of the local configuration
+	FunctionAnnotationLocalConfig = ConfigurationAnnotationDomain + "/local-config"
+
+	// Setting to true means we want this function configuration to be injected as a
+	// local configuration resource (local-config)
+	FunctionAnnotationInjectLocal = ConfigurationAnnotationDomain + "/inject-local"
+
+	// if set, the transformation will remove all the resources marked as local-config
+	FunctionAnnotationPruneLocal = ConfigurationAnnotationDomain + "/prune-local"
 )

pkg/utils/utils.go

@@ -1,6 +1,11 @@
 package utils
 
-import "sigs.k8s.io/kustomize/api/resource"
+import (
+	"sigs.k8s.io/kustomize/api/resource"
+	"sigs.k8s.io/kustomize/kyaml/kio/filters"
+	"sigs.k8s.io/kustomize/kyaml/kio/kioutil"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
 
 var buildAnnotations = []string{
 	BuildAnnotationPreviousKinds,
@@ -30,3 +35,15 @@ func RemoveBuildAnnotations(r *resource.Resource) {
 		panic(err)
 	}
 }
+
+func MakeResourceLocal(r *yaml.RNode) error {
+	annotations := r.GetAnnotations()
+
+	annotations[filters.LocalConfigAnnotation] = "true"
+	annotations[kioutil.PathAnnotation] = ".generated.yaml"
+	annotations[kioutil.LegacyPathAnnotation] = ".generated.yaml"
+	delete(annotations, FunctionAnnotationInjectLocal)
+	delete(annotations, FunctionAnnotationFunction)
+
+	return r.SetAnnotations(annotations)
+}