fix none() has no effect in update/aggregate / first

mongoengine/queryset/base.py

@@ -289,6 +289,9 @@ def create(self, **kwargs):
     def first(self):
         """Retrieve the first object matching the query."""
         queryset = self.clone()
+        if self._none or self._empty:
+            return None
+
         try:
             result = queryset[0]
         except IndexError:
@@ -551,6 +554,8 @@ def update(
 
         if write_concern is None:
             write_concern = {}
+        if self._none or self._empty:
+            return 0
 
         queryset = self.clone()
         query = queryset._query
@@ -673,6 +678,9 @@ def modify(
         if not update and not upsert and not remove:
             raise OperationError("No update parameters, must either update or remove")
 
+        if self._none or self._empty:
+            return None
+
         queryset = self.clone()
         query = queryset._query
         if not remove:
@@ -1305,6 +1313,10 @@ def aggregate(self, pipeline, *suppl_pipeline, **kwargs):
         user_pipeline += suppl_pipeline
 
         initial_pipeline = []
+        if self._none or self._empty:
+            initial_pipeline.append({"$limit": 1})
+            initial_pipeline.append({"$match": {"fldksjhkjhafds": "lasdjfhlasdhfk"}})
+
         if self._query:
             initial_pipeline.append({"$match": self._query})
 

tests/queryset/test_queryset.py

@@ -408,6 +408,19 @@ class A(Document):
         A.drop_collection()
         A().save()
 
+        # validate collection not empty
+        assert A.objects.count() == 1
+
+        # update operations
+        assert A.objects.none().update(s="1") == 0
+        assert A.objects.none().update_one(s="1") == 0
+        assert A.objects.none().modify(s="1") is None
+
+        # validate noting change by update operations
+        assert A.objects(s="1").count() == 0
+
+        # fetch queries
+        assert A.objects.none().first() is None
         assert list(A.objects.none()) == []
         assert list(A.objects.none().all()) == []
         assert list(A.objects.none().limit(1)) == []

tests/queryset/test_queryset_aggregation.py

@@ -276,6 +276,23 @@ class Aggr(Document):
             {"_id": agg2.id, "c": 0.0, "name": "Y"},
         ]
 
+    def test_queryset_aggregation_none(self):
+        class Person(Document):
+            name = StringField()
+            age = IntField()
+
+        Person.drop_collection()
+
+        p1 = Person(name="Isabella Luanna", age=16)
+        p2 = Person(name="Wilson Junior", age=21)
+        p3 = Person(name="Sandra Mara", age=37)
+        Person.objects.insert([p1, p2, p3])
+
+        pipeline = [{"$project": {"name": {"$toUpper": "$name"}}}]
+        data = Person.objects().none().order_by("name").aggregate(pipeline)
+
+        assert list(data) == []
+
 
 if __name__ == "__main__":
     unittest.main()