report result of delete operation after failed upload

The sanity check shouldn't replace the error message if there is already
one.

internal/backend/backend_retry.go

@@ -57,6 +57,7 @@ func (be *RetryBackend) retry(ctx context.Context, msg string, f func() error) e
 
 // Save stores the data in the backend under the given handle.
 func (be *RetryBackend) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
+	firstTry := true
 	return be.retry(ctx, fmt.Sprintf("Save(%v)", h), func() error {
 		err := rd.Rewind()
 		if err != nil {
@@ -65,13 +66,27 @@ func (be *RetryBackend) Save(ctx context.Context, h restic.Handle, rd restic.Rew
 
 		err = be.Backend.Save(ctx, h, rd)
 		if err == nil {
+			if !firstTry {
+				fi, err := be.Backend.Stat(ctx, h)
+				if err != nil {
+					return err
+				}
+				if fi.Size != rd.Length() {
+					return fmt.Errorf("Stat after save found unexpected length %q instead of %q", fi.Size, rd.Length())
+				}
+			}
+
 			return nil
 		}
+		firstTry = false
 
 		debug.Log("Save(%v) failed with error, removing file: %v", h, err)
 		rerr := be.Backend.Remove(ctx, h)
 		if rerr != nil {
 			debug.Log("Remove(%v) returned error: %v", h, err)
+			if be.Report != nil {
+				be.Report(fmt.Sprintf("Delete-failed-Save(%v)", h), err, time.Duration(0))
+			}
 		}
 
 		// return original error

internal/backend/backend_retry_test.go

@@ -16,6 +16,7 @@ import (
 func TestBackendSaveRetry(t *testing.T) {
 	buf := bytes.NewBuffer(nil)
 	errcount := 0
+	uploadSize := int64(0)
 	be := &mock.Backend{
 		SaveFn: func(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
 			if errcount == 0 {
@@ -28,9 +29,13 @@ func TestBackendSaveRetry(t *testing.T) {
 				return errors.New("injected error")
 			}
 
-			_, err := io.Copy(buf, rd)
+			var err error
+			uploadSize, err = io.Copy(buf, rd)
 			return err
 		},
+		StatFn: func(ctx context.Context, h restic.Handle) (restic.FileInfo, error) {
+			return restic.FileInfo{Name: h.Name, Size: uploadSize}, nil
+		},
 	}
 
 	retryBackend := NewRetryBackend(be, 10, nil)

internal/backend/s3/s3.go

@@ -277,7 +277,7 @@ func (be *Backend) Save(ctx context.Context, h restic.Handle, rd restic.RewindRe
 	debug.Log("%v -> %v bytes, err %#v: %v", objName, info.Size, err, err)
 
 	// sanity check
-	if err != nil && info.Size != rd.Length() {
+	if err == nil && info.Size != rd.Length() {
 		return errors.Errorf("wrote %d bytes instead of the expected %d bytes", info.Size, rd.Length())
 	}