make Value encode Decimal as Decimal128

Author: timgraham

django_mongodb/expressions.py

@@ -1,3 +1,6 @@
+from decimal import Decimal
+
+from bson import Decimal128
 from django.core.exceptions import EmptyResultSet, FullResultSet
 from django.db.models.expressions import (
     Case,
@@ -60,7 +63,10 @@ def when(self, compiler, connection):
 
 
 def value(self, compiler, connection):  # noqa: ARG001
-    return {"$literal": self.value}
+    value = self.value
+    if isinstance(value, Decimal):
+        value = Decimal128(value)
+    return {"$literal": value}
 
 
 def register_expressions():

django_mongodb/features.py

@@ -61,9 +61,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "annotations.tests.NonAggregateAnnotationTestCase.test_annotation_and_alias_filter_in_subquery",
         # Length of null considered zero rather than null.
         "db_functions.text.test_length.LengthTests.test_basic",
-        # annotating with Decimal() crashes: bson.errors.InvalidDocument:
-        # cannot encode object: Decimal('1'), of type: <class 'decimal.Decimal'>
-        "expressions_case.tests.CaseExpressionTests.test_annotate_filter_decimal",
         # Case(..., then=datetime.date()) crashes: bson.errors.InvalidDocument:
         # cannot encode object: datetime.date(2024, 5, 14), of type: <class 'datetime.date'>
         "expressions_case.tests.CaseDocumentationExamples.test_filter_example",