fix QuerySet.annotate() without values/value_list()

Also fix annotating with Value().

Author: timgraham

.github/workflows/test-python.yml

@@ -67,6 +67,7 @@ jobs:
       - name: Run tests
         run: >
           python3 django_repo/tests/runtests.py --settings mongodb_settings -v 2
+          annotations.tests.NonAggregateAnnotationTestCase.test_basic_annotation
           auth_tests.test_models.UserManagerTestCase
           backends.base.test_base.DatabaseWrapperTests
           basic

django_mongodb/compiler.py

@@ -22,8 +22,11 @@ def execute_sql(
         # QuerySet.count()
         if self.query.annotations == {"__count": Count("*")}:
             return [self.get_count()]
+        # Specify columns if there are any annotations so that annotations are
+        # computed via $project.
+        columns = self.get_columns() if self.query.annotations else None
         try:
-            query = self.build_query()
+            query = self.build_query(columns)
         except EmptyResultSet:
             return None
         return query.fetch()

django_mongodb/expressions.py

@@ -9,6 +9,11 @@ def value(self, compiler, connection):  # noqa: ARG001
     return self.value
 
 
+def value_agg(self, compiler, connection):  # noqa: ARG001
+    return {"$literal": self.value}
+
+
 def register_expressions():
     Col.as_mql = col
     Value.as_mql = value
+    Value.as_mql_agg = value_agg