lib/versioner: Improve error messages (fixes #7354) (#7357)

lib/api/api.go

@@ -1545,7 +1545,7 @@ func (s *service) postFolderVersionsRestore(w http.ResponseWriter, r *http.Reque
 		http.Error(w, err.Error(), 500)
 		return
 	}
-	sendJSON(w, ferr)
+	sendJSON(w, errorStringMap(ferr))
 }
 
 func (s *service) getFolderErrors(w http.ResponseWriter, r *http.Request) {
@@ -1839,6 +1839,14 @@ func shouldRegenerateCertificate(cert tls.Certificate) error {
 	return nil
 }
 
+func errorStringMap(errs map[string]error) map[string]*string {
+	out := make(map[string]*string, len(errs))
+	for s, e := range errs {
+		out[s] = errorString(e)
+	}
+	return out
+}
+
 func errorString(err error) *string {
 	if err != nil {
 		msg := err.Error()

lib/api/mocked_model_test.go

@@ -96,7 +96,7 @@ func (m *mockedModel) GetFolderVersions(folder string) (map[string][]versioner.F
 	return nil, nil
 }
 
-func (m *mockedModel) RestoreFolderVersions(folder string, versions map[string]time.Time) (map[string]string, error) {
+func (m *mockedModel) RestoreFolderVersions(folder string, versions map[string]time.Time) (map[string]error, error) {
 	return nil, nil
 }