Fix some tests.

Author: WaVEV

django_mongodb/compiler.py

@@ -1,8 +1,10 @@
 from django.core.exceptions import EmptyResultSet, FullResultSet
 from django.db import DatabaseError, IntegrityError, NotSupportedError
 from django.db.models import Count, Expression
-from django.db.models.aggregates import Aggregate
+from django.db.models.aggregates import Aggregate, Variance
 from django.db.models.expressions import Col, OrderBy, Value
+from django.db.models.functions.comparison import Coalesce
+from django.db.models.functions.math import Power
 from django.db.models.sql import compiler
 from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE, MULTI, ORDER_DIR, SINGLE
 from django.utils.functional import cached_property
@@ -45,7 +47,11 @@ def _prepare_expressions_for_pipeline(self, expression, target):
                 group[alias] = sub_expr.as_mql(self, self.connection)
                 replacing_expr = inner_column
 
-            sub_expr.as_mql(self, self.connection)
+            if isinstance(sub_expr, Count):
+                replacing_expr = Coalesce(replacing_expr, 0)
+            if isinstance(sub_expr, Variance):
+                replacing_expr = Power(replacing_expr, 2)
+
             replacements[sub_expr] = replacing_expr
         return replacements, group
 

django_mongodb/functions.py

@@ -140,17 +140,11 @@ def count(self, compiler, connection, **extra_context):
             node = self
             lhs_mql = process_lhs(self, compiler, connection)
             null_cond = {"$in": [{"$type": lhs_mql}, ["missing", "null"]]}
-            cond = {
-                "$cond": {"if": null_cond, "then": None, "else": lhs_mql if self.distinct else 1}
-            }
-        operator = "$sum"
-        return {operator: cond}
+            cond = {"$cond": {"if": null_cond, "then": 0, "else": lhs_mql if self.distinct else 1}}
+        return {"$sum": cond}
 
-    operator = "$size"
     lhs_mql = process_lhs(self, compiler, connection)
-
     exits_null = {"$cond": {"if": {"$in": [{"$literal": None}, lhs_mql]}, "then": -1, "else": 0}}
-
     return {"$add": [{"$size": lhs_mql}, exits_null]}
 
 

django_mongodb/operations.py

@@ -132,7 +132,7 @@ def convert_floatfield_value(self, value, expression, connection):
         return None if value is None else float(value)
 
     def convert_integerfield_value(self, value, expression, connection):
-        return None if value is None else float(value)
+        return None if value is None else int(value)
 
     def convert_jsonfield_value(self, value, expression, connection):
         """