Pass original invalid version storage error details into standardized errors

Signed-off-by: Riyaz Faizullabhoy <riyaz.faizullabhoy@docker.com>

server/errors/errors.go

@@ -44,6 +44,12 @@ var (
 		Description:    "An error occurred when attempting to apply an update at the storage layer.",
 		HTTPStatusCode: http.StatusInternalServerError,
 	})
+	ErrOldVersion = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:          "VERSION",
+		Message:        "A newer version of metadata is already available.",
+		Description:    "A newer version of the repository's metadata is already available in storage.",
+		HTTPStatusCode: http.StatusBadRequest,
+	})
 	ErrMetadataNotFound = errcode.Register(errGroup, errcode.ErrorDescriptor{
 		Value:          "METADATA_NOT_FOUND",
 		Message:        "You have requested metadata that does not exist.",

server/handlers/default.go

@@ -96,6 +96,11 @@ func atomicUpdateHandler(ctx context.Context, w http.ResponseWriter, r *http.Req
 	}
 	err = store.UpdateMany(gun, updates)
 	if err != nil {
+		// If we have an old version error, surface to user with error code
+		if _, ok := err.(storage.ErrOldVersion); ok {
+			return errors.ErrOldVersion.WithDetail(err)
+		}
+		// More generic storage update error, possibly due to attempted rollback
 		return errors.ErrUpdating.WithDetail(nil)
 	}
 	return nil

server/handlers/default_test.go

@@ -385,3 +385,43 @@ func TestAtomicUpdateNonValidationFailureNotPropagated(t *testing.T) {
 	assert.Equal(t, errors.ErrInvalidUpdate, errorObj.Code)
 	assert.Nil(t, errorObj.Detail)
 }
+
+type invalidVersionStore struct {
+	storage.MemStorage
+}
+
+func (s *invalidVersionStore) UpdateMany(_ string, _ []storage.MetaUpdate) error {
+	return storage.ErrOldVersion{}
+}
+
+// a non-validation failure, such as the storage failing, will be propagated
+// as a detail in the error (which gets serialized as the body of the response)
+func TestAtomicUpdateVersionErrorPropagated(t *testing.T) {
+	metaStore := storage.NewMemStorage()
+	gun := "testGUN"
+	vars := map[string]string{"imageName": gun}
+
+	kdb, repo, cs := testutils.EmptyRepo()
+	copyTimestampKey(t, kdb, metaStore, gun)
+	state := handlerState{store: &invalidVersionStore{*metaStore}, crypto: cs}
+
+	r, tg, sn, ts, err := testutils.Sign(repo)
+	assert.NoError(t, err)
+	rs, tgs, sns, _, err := testutils.Serialize(r, tg, sn, ts)
+	assert.NoError(t, err)
+
+	req, err := store.NewMultiPartMetaRequest("", map[string][]byte{
+		data.CanonicalRootRole:     rs,
+		data.CanonicalTargetsRole:  tgs,
+		data.CanonicalSnapshotRole: sns,
+	})
+
+	rw := httptest.NewRecorder()
+
+	err = atomicUpdateHandler(getContext(state), rw, req, vars)
+	assert.Error(t, err)
+	errorObj, ok := err.(errcode.Error)
+	assert.True(t, ok, "Expected an errcode.Error, got %v", err)
+	assert.Equal(t, errors.ErrOldVersion, errorObj.Code)
+	assert.Equal(t, storage.ErrOldVersion{}, errorObj.Detail)
+}