Fix Limit 0 QuerySet Empty List (#767)

* fix: debug condition check not none limit count

* test: write a test for check zero limit empty list

* fix: debug assert check empty list with is keyword

ormar/queryset/queries/limit_query.py

@@ -20,6 +20,8 @@ class LimitQuery:
         :return: modified query
         :rtype: sqlalchemy.sql.selectable.Select
         """
-        if self.limit_count:
+
+        if self.limit_count is not None:
             expr = expr.limit(self.limit_count)
+
         return expr

ormar/queryset/queryset.py

@@ -282,10 +282,10 @@ class QuerySet(Generic[T]):
             filter_clauses=self.filter_clauses,
             exclude_clauses=self.exclude_clauses,
             offset=offset or self.query_offset,
-            limit_count=limit or self.limit_count,
             excludable=self._excludable,
             order_bys=order_bys or self.order_bys,
             limit_raw_sql=self.limit_sql_raw,
+            limit_count=limit if limit is not None else self.limit_count,
         )
         exp = qry.build_select_expression()
         # print("\n", exp.compile(compile_kwargs={"literal_binds": True}))

tests/test_queries/test_pagination.py

@@ -47,6 +47,18 @@ def create_test_database():
     metadata.drop_all(engine)
 
 
+@pytest.mark.asyncio
+async def test_limit_zero():
+    async with database:
+        async with database.transaction(force_rollback=True):
+            for i in range(5):
+                await Car(name=f"{i}").save()
+
+            cars = await Car.objects.limit(0).all()
+            assert cars == []
+            assert len(cars) == 0
+
+
 @pytest.mark.asyncio
 async def test_pagination_errors():
     async with database: