Move EmptyResultSet handle to process_lhs

Author: WaVEV

django_mongodb_backend/aggregates.py

@@ -1,4 +1,3 @@
-from django.core.exceptions import EmptyResultSet, FullResultSet
 from django.db import NotSupportedError
 from django.db.models.aggregates import (
     Aggregate,
@@ -30,12 +29,6 @@ def aggregate(self, compiler, connection, operator=None, resolve_inner_expressio
                 # Skip rows that don't meet the criteria.
                 default=Remove(),
             )
-        except FullResultSet:
-            # TODO: CHECK UNIT TEST REACH HERE.
-            pass
-        except EmptyResultSet:
-            # TODO: CHECK UNIT TEST REACH HERE.
-            agg_expression = Remove()
     if lhs_mql is None:
         lhs_mql = agg_expression.as_mql(compiler, connection, as_expr=True)
     if resolve_inner_expression:
@@ -63,11 +56,7 @@ def count(self, compiler, connection, resolve_inner_expression=False):
                     WhereNode(conditions),
                     then=agg_expression if self.distinct else Value(1),
                 )
-                inner_expression = Case(condition)
-            except FullResultSet:
-                inner_expression = agg_expression if self.distinct else Value(1)
-            except EmptyResultSet:
-                inner_expression = Remove() if self.distinct else Value(0)
+                inner_expression = Case(condition, default=Remove())
         else:
             inner_expression = Case(
                 When(WhereNode(conditions), then=agg_expression if self.distinct else Value(1)),

django_mongodb_backend/query_utils.py

@@ -1,4 +1,4 @@
-from django.core.exceptions import FullResultSet
+from django.core.exceptions import EmptyResultSet, FullResultSet
 from django.db.models import F
 from django.db.models.expressions import CombinedExpression, Func, Value
 from django.db.models.sql.query import Query
@@ -19,6 +19,8 @@ def process_lhs(node, compiler, connection, as_expr=False):
                 result.append(expr.as_mql(compiler, connection, as_expr=as_expr))
             except FullResultSet:
                 result.append(Value(True).as_mql(compiler, connection, as_expr=as_expr))
+            except EmptyResultSet:
+                result.append(Value(None).as_mql(compiler, connection, as_expr=as_expr))
         return result
     # node is a Transform with just one source expression, aliased as "lhs".
     if is_direct_value(node.lhs):