async put - throw the new UniqueViolationException when appropriate

Author: Ivan Dlugos

objectbox/lib/src/native/box.dart

@@ -423,7 +423,9 @@ class _AsyncBoxHelper {
       if (message == null) {
         completer.complete(newId);
       } else if (message is String) {
-        completer.completeError(ObjectBoxException(message));
+        completer.completeError(message.startsWith('Unique constraint')
+            ? UniqueViolationException(message)
+            : ObjectBoxException(message));
       } else {
         completer.completeError(ObjectBoxException(
             'Unknown message type (${message.runtimeType}: $message'));

objectbox/test/box_test.dart

@@ -95,12 +95,14 @@ void main() {
       final future = box.putAsync(object);
       expect(
           future,
-          throwsA(predicate((ObjectBoxException e) =>
+          throwsA(predicate((UniqueViolationException e) =>
               e.toString().contains('Unique constraint'))));
-      // paranoia, should already have waited on the above [expect()]
+
       try {
+        // paranoia, should already have waited on the above [expect()]
         await future;
       } catch (_) {}
+
       expect(object.id, isNull); // ID must remain unassigned
     }
   });