add Value support

Author: timgraham

django_mongodb/expressions.py

@@ -1,9 +1,14 @@
-from django.db.models.expressions import Col
+from django.db.models.expressions import Col, Value
 
 
 def col(self, compiler, connection):  # noqa: ARG001
     return f"${self.target.column}"
 
 
+def value(self, compiler, connection):  # noqa: ARG001
+    return self.value
+
+
 def register_expressions():
     Col.as_mql = col
+    Value.as_mql = value

django_mongodb/features.py

@@ -140,9 +140,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
             "lookup.tests.LookupQueryingTests.test_filter_exists_lhs",
             # QuerySet.alias() doesn't work.
             "lookup.tests.LookupQueryingTests.test_alias",
-            # Value() not supported.
-            "lookup.tests.LookupQueryingTests.test_annotate_literal_greater_than_field",
-            "lookup.tests.LookupQueryingTests.test_annotate_value_greater_than_value",
             # annotate() with combined expressions doesn't work:
             # 'WhereNode' object has no attribute 'field'
             "lookup.tests.LookupQueryingTests.test_combined_annotated_lookups_in_filter",