SERVER-29506 Require $changeNotification to be the first stage.

This reverts commit babab967892f81f3107903cb41672503de791998.

1 files changed, 8 insertions, 2 deletions

diff --git a/src/mongo/db/pipeline/document_source_mock.h b/src/mongo/db/pipeline/document_source_mock.h
index 9236e55ad62..513994cd599 100644
--- a/src/mongo/db/pipeline/document_source_mock.h
+++ b/src/mongo/db/pipeline/document_source_mock.h
@@ -48,9 +48,15 @@ public:
     const char* getSourceName() const override;
     Value serialize(
         boost::optional<ExplainOptions::Verbosity> explain = boost::none) const override;
-    InitialSourceType getInitialSourceType() const override {
-        return InitialSourceType::kInitialSource;
+
+    StageConstraints constraints() const override {
+        StageConstraints constraints;
+        constraints.requiredPosition = StageConstraints::PositionRequirement::kFirst;
+        constraints.requiresInputDocSource = false;
+        constraints.isAllowedInsideFacetStage = false;
+        return constraints;
     }
+
     BSONObjSet getOutputSorts() override {
         return sorts;
     }