fix isnull lookup when querying joined tables

Author: WaVEV

django_mongodb/base.py

@@ -82,14 +82,26 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         "endswith": "LIKE '%%' || {}",
         "iendswith": "LIKE '%%' || UPPER({})",
     }
+
+    def _isnull_operator(a, b):
+        is_null = {
+            "$or": [
+                # The path does not exist (i.e. is "missing")
+                {"$eq": [{"$type": a}, "missing"]},
+                # or the value is None.
+                {"$eq": [a, None]},
+            ]
+        }
+        return is_null if b else {"$not": is_null}
+
     mongo_operators = {
         "exact": lambda a, b: {"$eq": [a, b]},
         "gt": lambda a, b: {"$gt": [a, b]},
         "gte": lambda a, b: {"$gte": [a, b]},
         "lt": lambda a, b: {"$lt": [a, b]},
         "lte": lambda a, b: {"$lte": [a, b]},
         "in": lambda a, b: {"$in": [a, b]},
-        "isnull": lambda a, b: {("$eq" if b else "$ne"): [a, None]},
+        "isnull": _isnull_operator,
         "range": lambda a, b: {"$and": [{"$gte": [a, b[0]]}, {"$lte": [a, b[1]]}]},
         "iexact": lambda a, b: regex_match(a, ("^", b, {"$literal": "$"}), insensitive=True),
         "startswith": lambda a, b: regex_match(a, ("^", b)),

django_mongodb/features.py

@@ -77,34 +77,18 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # decimal.InvalidOperation: [<class 'decimal.ConversionSyntax'>]
         "lookup.tests.LookupTests.test_lookup_rhs",
         # Wrong results in queries with multiple tables.
-        "annotations.tests.NonAggregateAnnotationTestCase.test_annotation_aggregate_with_m2o",
         "annotations.tests.NonAggregateAnnotationTestCase.test_annotation_reverse_m2m",
         "annotations.tests.NonAggregateAnnotationTestCase.test_annotation_with_m2m",
         "annotations.tests.NonAggregateAnnotationTestCase.test_chaining_annotation_filter_with_m2m",
         "annotations.tests.NonAggregateAnnotationTestCase.test_mti_annotations",
         "expressions.test_queryset_values.ValuesExpressionsTests.test_values_list_expression",
         "expressions.test_queryset_values.ValuesExpressionsTests.test_values_list_expression_flat",
         "expressions.tests.IterableLookupInnerExpressionsTests.test_expressions_in_lookups_join_choice",
-        "expressions_case.tests.CaseExpressionTests.test_join_promotion",
-        "expressions_case.tests.CaseExpressionTests.test_join_promotion_multiple_annotations",
         "ordering.tests.OrderingTests.test_order_by_grandparent_fk_with_expression_in_default_ordering",
         "ordering.tests.OrderingTests.test_order_by_parent_fk_with_expression_in_default_ordering",
         "ordering.tests.OrderingTests.test_order_by_ptr_field_with_default_ordering_by_expression",
-        "queries.tests.NullJoinPromotionOrTest.test_isnull_filter_promotion",
-        "queries.tests.NullJoinPromotionOrTest.test_ticket_21366",
-        "queries.tests.NullJoinPromotionOrTest.test_ticket_21748",
         "queries.tests.Queries1Tests.test_order_by_tables",
-        "queries.tests.Queries1Tests.test_ticket1050",
-        "queries.tests.Queries1Tests.test_ticket2400",
         "queries.tests.Queries1Tests.test_ticket4358",
-        "queries.tests.Queries1Tests.test_ticket_10790_1",
-        "queries.tests.Queries1Tests.test_ticket_10790_4",
-        "queries.tests.Queries1Tests.test_ticket_10790_6",
-        "queries.tests.Queries1Tests.test_ticket_10790_7",
-        "queries.tests.Queries4Tests.test_ticket15316_exclude_false",
-        "queries.tests.Queries4Tests.test_ticket15316_filter_true",
-        "queries.tests.Queries4Tests.test_ticket15316_one2one_exclude_false",
-        "queries.tests.Queries4Tests.test_ticket15316_one2one_filter_true",
         "queries.tests.Queries4Tests.test_ticket7095",
         "queries.tests.TestTicket24605.test_ticket_24605",
         "queries.tests.TestInvalidValuesRelation.test_invalid_values",
@@ -113,9 +97,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "annotations.tests.AliasTests.test_order_by_alias_aggregate",
         # annotate() + values_list() + order_by() loses annotated value.
         "expressions_case.tests.CaseExpressionTests.test_annotate_values_not_in_order_by",
-        # Querying the reverse side of a foreign key for None returns no
-        # results: https://github.com/mongodb-labs/django-mongodb/issues/76
-        "one_to_one.tests.OneToOneTests.test_filter_one_to_one_relations",
         # pymongo.errors.OperationFailure: the limit must be positive
         "queries.tests.WeirdQuerysetSlicingTests.test_tickets_7698_10202",
         # QuerySet.explain() not implemented: