Address review comments

Signed-off-by: Sergen Yalçın <yalcinsergen97@gmail.com>

pkg/migration/filesystem.go

@@ -3,7 +3,6 @@ package migration
 import (
 	"bytes"
 	"fmt"
-	"log"
 	"os"
 	"path/filepath"
 
@@ -40,45 +39,44 @@ func NewFileSystemSource(dir string, opts ...FileSystemSourceOption) (*FileSyste
 		f(fs)
 	}
 
-	files, err := fs.afero.ReadDir(dir)
-	if err != nil {
-		log.Fatal(err)
-	}
+	if err := filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return errors.Wrap(err, fmt.Sprintf("cannot read %s", path))
+		}
 
-	for _, file := range files {
-		if file.IsDir() {
-			continue
+		if info.IsDir() {
+			return nil
 		}
-		data, err := fs.afero.ReadFile(filepath.Join(dir, file.Name()))
+
+		data, err := fs.afero.ReadFile(path)
 		if err != nil {
-			return nil, err
+			return errors.Wrap(err, "cannot read source file")
 		}
 
 		decoder := yaml.NewYAMLOrJSONDecoder(bytes.NewBufferString(string(data)), 1024)
 		u := &unstructured.Unstructured{}
 		if err := decoder.Decode(&u); err != nil {
-			if err != nil {
-				return nil, err
-			}
+			return errors.Wrap(err, "cannot decode read data")
 		}
 
 		fs.items = append(fs.items, UnstructuredWithMetadata{
 			Object: *u,
 			Metadata: Metadata{
-				Path: filepath.Join(dir, file.Name()),
+				Path: path,
 			},
 		})
+
+		return nil
+	}); err != nil {
+		return nil, errors.Wrap(err, "cannot read source directory")
 	}
 
 	return fs, nil
 }
 
 // HasNext checks the next item
 func (fs *FileSystemSource) HasNext() (bool, error) {
-	if fs.index < len(fs.items) {
-		return true, nil
-	}
-	return false, nil
+	return fs.index < len(fs.items), nil
 }
 
 // Next returns the next item of slice
@@ -88,7 +86,7 @@ func (fs *FileSystemSource) Next() (UnstructuredWithMetadata, error) {
 		fs.index++
 		return item, nil
 	}
-	return UnstructuredWithMetadata{}, errors.New("failed to get next element")
+	return UnstructuredWithMetadata{}, errors.New("no more elements")
 }
 
 // FileSystemTarget is a target implementation to write/patch/delete resources to file system
@@ -121,26 +119,26 @@ func NewFileSystemTarget(opts ...FileSystemTargetOption) *FileSystemTarget {
 func (ft *FileSystemTarget) Put(o UnstructuredWithMetadata) error {
 	b, err := sigsyaml.Marshal(o.Object.Object)
 	if err != nil {
-		return err
+		return errors.Wrap(err, "cannot marshal object")
 	}
 	if o.Metadata.Parents != "" {
 		f, err := ft.afero.OpenFile(o.Metadata.Path, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600)
 		if err != nil {
-			return err
+			return errors.Wrap(err, "cannot open file")
 		}
 
 		defer f.Close() //nolint:errcheck
 
 		if _, err = f.WriteString(fmt.Sprintf("\n---\n\n%s", string(b))); err != nil {
-			return err
+			return errors.Wrap(err, "cannot write file")
 		}
 	} else {
 		f, err := ft.afero.Create(o.Metadata.Path)
 		if err != nil {
-			return err
+			return errors.Wrap(err, "cannot create file")
 		}
 		if _, err := f.Write(b); err != nil {
-			return err
+			return errors.Wrap(err, "cannot write file")
 		}
 	}
 

pkg/migration/kubernetes.go

@@ -20,6 +20,13 @@ type KubernetesSource struct {
 }
 
 // NewKubernetesSource returns a KubernetesSource
+// DynamicClient is used here to query resources.
+// Elements of gvks (slice of GroupVersionKind) are passed to the Dynamic Client
+// in a loop to get list of resources.
+// An example element of gvks slice:
+// Group:   "ec2.aws.upbound.io",
+// Version: "v1beta1",
+// Kind:    "VPC",
 func NewKubernetesSource(dynamicClient dynamic.Interface, gvks []schema.GroupVersionKind) (*KubernetesSource, error) {
 	ks := &KubernetesSource{
 		dynamicClient: dynamicClient,
@@ -34,7 +41,7 @@ func NewKubernetesSource(dynamicClient dynamic.Interface, gvks []schema.GroupVer
 			})
 		unstructuredList, err := ri.List(context.TODO(), metav1.ListOptions{})
 		if err != nil {
-			return nil, err
+			return nil, errors.Wrap(err, "cannot list resources")
 		}
 		for _, u := range unstructuredList.Items {
 			ks.items = append(ks.items, UnstructuredWithMetadata{
@@ -50,10 +57,7 @@ func NewKubernetesSource(dynamicClient dynamic.Interface, gvks []schema.GroupVer
 
 // HasNext checks the next item
 func (ks *KubernetesSource) HasNext() (bool, error) {
-	if ks.index < len(ks.items) {
-		return true, nil
-	}
-	return false, nil
+	return ks.index < len(ks.items), nil
 }
 
 // Next returns the next item of slice
@@ -63,18 +67,18 @@ func (ks *KubernetesSource) Next() (UnstructuredWithMetadata, error) {
 		ks.index++
 		return item, nil
 	}
-	return UnstructuredWithMetadata{}, errors.New("failed to get next element")
+	return UnstructuredWithMetadata{}, errors.New("no more elements")
 }
 
 // InitializeDynamicClient returns a dynamic client
 func InitializeDynamicClient(kubeconfigPath string) (dynamic.Interface, error) {
 	config, err := clientcmd.BuildConfigFromFlags("", kubeconfigPath)
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrap(err, "cannot create rest config object")
 	}
 	dynamicClient, err := dynamic.NewForConfig(config)
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrap(err, "cannot initialize dynamic client")
 	}
 	return dynamicClient, nil
 }