Fix when selecting with an MSFList

multiselectfield/utils.py

@@ -14,8 +14,13 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with this programe.  If not, see <http://www.gnu.org/licenses/>.
 
-import sys
+from __future__ import annotations
 
+import sys
+from collections import UserList
+from typing import Optional, Union
+
+from django.db.models.sql.query import Query
 
 if sys.version_info[0] == 2:
     string = basestring  # noqa: F821
@@ -25,6 +30,16 @@ else:
     string_type = string
 
 
+class _FakeSqlVal(UserList):
+
+    contains_aggregate = False
+    contains_column_references = False
+    contains_over_clause = False
+
+    def __str__(self):
+        return ','.join(map(str, self))
+
+
 class MSFList(list):
 
     def __init__(self, choices, *args, **kwargs):
@@ -35,6 +50,16 @@ class MSFList(list):
         msg_list = [msgl.choices.get(int(i)) if i.isdigit() else msgl.choices.get(i) for i in msgl]
         return u', '.join([string_type(s) for s in msg_list])
 
+    def resolve_expression(
+            self, query: Query = None, allow_joins: bool = True,
+            reuse: Optional[bool] = None, summarize: bool = False,
+            for_save: bool = False) -> Union[list, _FakeSqlVal]:
+        if for_save:
+            result = _FakeSqlVal(self)
+        else:
+            result = list(self)
+        return result
+
     if sys.version_info < (3,):
         def __unicode__(self, msgl):
             return self.__str__(msgl)