address comments

pkg/plugins/execplugin.go

@@ -134,17 +134,7 @@ func (p *ExecPlugin) writeConfig() (string, error) {
 }
 
 func (p *ExecPlugin) Generate() (resmap.ResMap, error) {
-	args, err := p.getArgs()
-	if err != nil {
-		return nil, err
-	}
-	cmd := exec.Command(p.name, args...)
-	cmd.Env = p.getEnv()
-	cmd.Stderr = os.Stderr
-	if _, err := os.Stat(p.ldr.Root()); err == nil {
-		cmd.Dir = p.ldr.Root()
-	}
-	output, err := cmd.Output()
+	output, err := p.invokePlugin(nil)
 	if err != nil {
 		return nil, err
 	}
@@ -152,30 +142,42 @@ func (p *ExecPlugin) Generate() (resmap.ResMap, error) {
 }
 
 func (p *ExecPlugin) Transform(rm resmap.ResMap) error {
-	args, err := p.getArgs()
+	// add ResIds as annotations to all objects so that we can add them back
+	inputRM, err := p.getResMapWithIdAnnotation(rm)
 	if err != nil {
 		return err
 	}
 
-	inputRM := p.getResMapWithIdAnnotation(rm)
+	// encode the ResMap so it can be fed to the plugin
 	resources, err := inputRM.EncodeAsYaml()
 	if err != nil {
 		return err
 	}
 
-	cmd := exec.Command(p.name, args...)
-	cmd.Env = p.getEnv()
-	cmd.Stdin = bytes.NewReader(resources)
-	cmd.Stderr = os.Stderr
-	if _, err := os.Stat(p.ldr.Root()); err == nil {
-		cmd.Dir = p.ldr.Root()
-	}
-	output, err := cmd.Output()
+	// invoke the plugin with resources as the input
+	output, err := p.invokePlugin(resources)
 	if err != nil {
 		return err
 	}
 
-	return p.parseResMapFromOutput(output, rm)
+	// update the original ResMap based on the output
+	return p.updateResMapValues(output, rm)
+}
+
+// invokePlugin invokes the plugin
+func (p *ExecPlugin) invokePlugin(input []byte) ([]byte, error) {
+	args, err := p.getArgs()
+	if err != nil {
+		return nil, err
+	}
+	cmd := exec.Command(p.name, args...)
+	cmd.Env = p.getEnv()
+	cmd.Stdin = bytes.NewReader(input)
+	cmd.Stderr = os.Stderr
+	if _, err := os.Stat(p.ldr.Root()); err == nil {
+		cmd.Dir = p.ldr.Root()
+	}
+	return cmd.Output()
 }
 
 // The first arg is always the absolute path to a temporary file
@@ -196,32 +198,46 @@ func (p *ExecPlugin) getEnv() []string {
 	return env
 }
 
-func (p *ExecPlugin) getResMapWithIdAnnotation(rm resmap.ResMap) resmap.ResMap {
+// Returns a new copy of the given ResMap with the ResIds annotated in each Resource
+func (p *ExecPlugin) getResMapWithIdAnnotation(rm resmap.ResMap) (resmap.ResMap, error) {
 	inputRM := rm.DeepCopy(p.rf.RF())
 	for id, r := range inputRM {
+		idString, err := yaml.Marshal(id)
+		if err != nil {
+			return nil, err
+		}
 		annotations := r.GetAnnotations()
 		if annotations == nil {
-			annotations = make(map[string]string)
+			annotations = map[string]string{
+				idAnnotation: string(idString),
+			}
+			r.SetAnnotations(annotations)
 		}
-		annotations[idAnnotation] = id.String()
-		r.SetAnnotations(annotations)
+		annotations[idAnnotation] = string(idString)
 	}
-	return inputRM
+	return inputRM, nil
 }
 
-func (p *ExecPlugin) parseResMapFromOutput(output []byte, rm resmap.ResMap) error {
+/*
+updateResMapValues updates the Resource value in the given ResMap
+with the emitted Resource values in output.
+*/
+func (p *ExecPlugin) updateResMapValues(output []byte, rm resmap.ResMap) error {
 	outputRM, err := p.rf.NewResMapFromBytes(output)
 	if err != nil {
 		return err
 	}
 	for _, r := range outputRM {
+		// for each emitted Resource, find the matching Resource in the original ResMap
+		// using its id
 		annotations := r.GetAnnotations()
 		idString, ok := annotations[idAnnotation]
 		if !ok {
 			return fmt.Errorf("the transformer %s should not remove annotation %s",
 				p.name, idAnnotation)
 		}
-		id, err := resid.NewResIdFromString(idString)
+		id := resid.ResId{}
+		err := yaml.Unmarshal([]byte(idString), &id)
 		if err != nil {
 			return err
 		}
@@ -229,8 +245,14 @@ func (p *ExecPlugin) parseResMapFromOutput(output []byte, rm resmap.ResMap) erro
 		if !ok {
 			return fmt.Errorf("unable to find id %s in resource map", id.String())
 		}
+		// remove the annotation set by Kustomize to track the resource
 		delete(annotations, idAnnotation)
+		if len(annotations) == 0 {
+			annotations = nil
+		}
 		r.SetAnnotations(annotations)
+
+		// update the ResMap resource value with the transformed object
 		res.Kunstructured = r.Kunstructured
 	}
 	return nil