Fix bulk delete operation in S3 driver.

The original implementation of bulk delete was omitting the error check
returned from the bulk operation thus potentially not cathing errors
that may have occurred when deleting individual S3 keys.

This commit introduces storagedriver.Errors type that allows to return
multierrors as a single error from any storage driver implementation.

Signed-off-by: Milos Gajdos <milosthegajdos@gmail.com>

registry/storage/driver/s3-aws/s3.go

@@ -15,6 +15,7 @@ import (
 	"bytes"
 	"context"
 	"crypto/tls"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -937,7 +938,7 @@ func (d *driver) Delete(ctx context.Context, path string) error {
 			// by default the response returns up to 1,000 key names. The response _might_ contain fewer keys but it will never contain more.
 			// 10000 keys is coincidentally (?) also the max number of keys that can be deleted in a single Delete operation, so we'll just smack
 			// Delete here straight away and reset the object slice when successful.
-			_, err = d.S3.DeleteObjects(&s3.DeleteObjectsInput{
+			resp, err := d.S3.DeleteObjects(&s3.DeleteObjectsInput{
 				Bucket: aws.String(d.Bucket),
 				Delete: &s3.Delete{
 					Objects: s3Objects,
@@ -948,6 +949,18 @@ func (d *driver) Delete(ctx context.Context, path string) error {
 				return err
 			}
 
+			if len(resp.Errors) > 0 {
+				// NOTE: AWS SDK s3.Error does not implement error interface which
+				// is pretty intensely sad, so we have to do away with this for now.
+				errs := make([]error, 0, len(resp.Errors))
+				for _, err := range resp.Errors {
+					errs = append(errs, errors.New(err.String()))
+				}
+				return storagedriver.Errors{
+					DriverName: driverName,
+					Errs:       errs,
+				}
+			}
 		}
 		// NOTE: we don't want to reallocate
 		// the slice so we simply "reset" it

registry/storage/driver/storagedriver.go

@@ -169,3 +169,27 @@ type Error struct {
 func (err Error) Error() string {
 	return fmt.Sprintf("%s: %s", err.DriverName, err.Enclosed)
 }
+
+// Errors provides the envelope for multiple errors
+// for use within the storagedriver implementations.
+type Errors struct {
+	DriverName string
+	Errs       []error
+}
+
+var _ error = Errors{}
+
+func (e Errors) Error() string {
+	switch len(e.Errs) {
+	case 0:
+		return "<nil>"
+	case 1:
+		return e.Errs[0].Error()
+	default:
+		msg := "errors:\n"
+		for _, err := range e.Errs {
+			msg += err.Error() + "\n"
+		}
+		return msg
+	}
+}