fix "'Ref' object has no attribute 'as_mql'" query crash

Author: timgraham

django_mongodb/expressions.py

@@ -10,6 +10,7 @@
     CombinedExpression,
     ExpressionWrapper,
     NegatedExpression,
+    Ref,
     Subquery,
     Value,
     When,
@@ -66,6 +67,10 @@ def query(self, compiler, connection):  # noqa: ARG001
     raise NotSupportedError("Using a QuerySet in annotate() is not supported on MongoDB.")
 
 
+def ref(self, compiler, connection):  # noqa: ARG001
+    return self.refs
+
+
 def subquery(self, compiler, connection):  # noqa: ARG001
     raise NotSupportedError(f"{self.__class__.__name__} is not supported on MongoDB.")
 
@@ -97,6 +102,7 @@ def register_expressions():
     ExpressionWrapper.as_mql = expression_wrapper
     NegatedExpression.as_mql = negated_expression
     Query.as_mql = query
+    Ref.as_mql = ref
     Subquery.as_mql = subquery
     When.as_mql = when
     Value.as_mql = value

django_mongodb/features.py

@@ -67,8 +67,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # pymongo.errors.OperationFailure:  $multiply only supports numeric
         # types, not date. (should be wrapped in DatabaseError).
         "expressions.tests.FTimeDeltaTests.test_invalid_operator",
-        # 'Ref' object has no attribute 'as_mql'.
-        "expressions.tests.BasicExpressionsTests.test_aggregate_subquery_annotation",
     }
     # $bitAnd, #bitOr, and $bitXor are new in MongoDB 6.3.
     _django_test_expected_failures_bitwise = {
@@ -251,6 +249,7 @@ def django_test_expected_failures(self):
             "annotations.tests.NonAggregateAnnotationTestCase.test_full_expression_annotation_with_aggregation",
             "annotations.tests.NonAggregateAnnotationTestCase.test_grouping_by_q_expression_annotation",
             "annotations.tests.NonAggregateAnnotationTestCase.test_q_expression_annotation_with_aggregation",
+            "expressions.tests.BasicExpressionsTests.test_aggregate_subquery_annotation",
             "expressions.tests.FieldTransformTests.test_month_aggregation",
             "expressions_case.tests.CaseDocumentationExamples.test_conditional_aggregation_example",
             # Func not implemented.