improve walk function on returning result

image/config.go

@@ -53,15 +53,10 @@ func findConfig(w walker, d *descriptor) (*config, error) {
 	var c config
 	cpath := filepath.Join("blobs", d.normalizeDigest())
 
-	f := func(path string, info os.FileInfo, r io.Reader) error {
-		if info.IsDir() {
-			return nil
+	if err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
+		if info.IsDir() || filepath.Clean(path) != cpath {
+			return fmt.Errorf("%s: config not found", cpath)
 		}
-
-		if filepath.Clean(path) != cpath {
-			return nil
-		}
-
 		buf, err := ioutil.ReadAll(r)
 		if err != nil {
 			return errors.Wrapf(err, "%s: error reading config", path)
@@ -75,18 +70,10 @@ func findConfig(w walker, d *descriptor) (*config, error) {
 			return err
 		}
 
-		return errEOW
-	}
-
-	switch err := w.walk(f); err {
-	case nil:
-		return nil, fmt.Errorf("%s: config not found", cpath)
-	case errEOW:
-		// found, continue below
-	default:
+		return nil
+	}); err != nil {
 		return nil, err
 	}
-
 	return &c, nil
 }
 

image/descriptor.go

@@ -41,58 +41,40 @@ func findDescriptor(w walker, name string) (*descriptor, error) {
 	var d descriptor
 	dpath := filepath.Join("refs", name)
 
-	f := func(path string, info os.FileInfo, r io.Reader) error {
-		if info.IsDir() {
-			return nil
-		}
-
-		if filepath.Clean(path) != dpath {
-			return nil
+	if err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
+		if info.IsDir() || filepath.Clean(path) != dpath {
+			return fmt.Errorf("%s: descriptor not found", dpath)
 		}
 
 		if err := json.NewDecoder(r).Decode(&d); err != nil {
 			return err
 		}
 
-		return errEOW
-	}
-
-	switch err := w.walk(f); err {
-	case nil:
-		return nil, fmt.Errorf("%s: descriptor not found", dpath)
-	case errEOW:
-		// found, continue below
-	default:
+		return nil
+	}); err != nil {
 		return nil, err
 	}
 
 	return &d, nil
 }
 
 func (d *descriptor) validate(w walker) error {
-	f := func(path string, info os.FileInfo, r io.Reader) error {
+	if err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
 		if info.IsDir() {
-			return nil
+			return fmt.Errorf("%s: not found", d.normalizeDigest())
 		}
 
 		digest, err := filepath.Rel("blobs", filepath.Clean(path))
 		if err != nil || d.normalizeDigest() != digest {
-			return nil // ignore
+			return fmt.Errorf("%s: not found", d.normalizeDigest())
 		}
 
 		if err := d.validateContent(r); err != nil {
 			return err
 		}
 
-		return errEOW
-	}
-
-	switch err := w.walk(f); err {
-	case nil:
-		return fmt.Errorf("%s: not found", d.normalizeDigest())
-	case errEOW:
-		// found, continue below
-	default:
+		return nil
+	}); err != nil {
 		return errors.Wrapf(err, "%s: validation failed", d.normalizeDigest())
 	}
 

image/manifest.go

@@ -40,13 +40,9 @@ func findManifest(w walker, d *descriptor) (*manifest, error) {
 	var m manifest
 	mpath := filepath.Join("blobs", d.normalizeDigest())
 
-	f := func(path string, info os.FileInfo, r io.Reader) error {
-		if info.IsDir() {
-			return nil
-		}
-
-		if filepath.Clean(path) != mpath {
-			return nil
+	if err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
+		if info.IsDir() || filepath.Clean(path) != mpath {
+			return fmt.Errorf("%s: manifest not found", mpath)
 		}
 
 		buf, err := ioutil.ReadAll(r)
@@ -66,15 +62,8 @@ func findManifest(w walker, d *descriptor) (*manifest, error) {
 			return fmt.Errorf("%s: no layers found", path)
 		}
 
-		return errEOW
-	}
-
-	switch err := w.walk(f); err {
-	case nil:
-		return nil, fmt.Errorf("%s: manifest not found", mpath)
-	case errEOW:
-		// found, continue below
-	default:
+		return nil
+	}); err != nil {
 		return nil, err
 	}
 
@@ -101,25 +90,22 @@ func (m *manifest) unpack(w walker, dest string) error {
 			continue
 		}
 
-		f := func(path string, info os.FileInfo, r io.Reader) error {
+		if err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
 			if info.IsDir() {
-				return nil
+				return fmt.Errorf("%s: blob digest not found", d.normalizeDigest())
 			}
 
 			dd, err := filepath.Rel("blobs", filepath.Clean(path))
 			if err != nil || d.normalizeDigest() != dd {
-				return nil // ignore
+				return fmt.Errorf("%s: blob digest not found", d.normalizeDigest())
 			}
 
 			if err := unpackLayer(dest, r); err != nil {
 				return errors.Wrap(err, "error extracting layer")
 			}
 
-			return errEOW
-		}
-
-		err := w.walk(f)
-		if err != nil && err != errEOW {
+			return nil
+		}); err != nil {
 			return err
 		}
 	}

image/walker.go

@@ -16,18 +16,13 @@ package image
 
 import (
 	"archive/tar"
-	"fmt"
 	"io"
 	"os"
 	"path/filepath"
 
 	"github.com/pkg/errors"
 )
 
-var (
-	errEOW = fmt.Errorf("end of walk") // error to signal stop walking
-)
-
 // walkFunc is a function type that gets called for each file or directory visited by the Walker.
 type walkFunc func(path string, _ os.FileInfo, _ io.Reader) error