1 files changed, 24 insertions, 0 deletions
diff --git a/src/mongo/bson/mutable/document.cpp b/src/mongo/bson/mutable/document.cpp
index 6ef13e1de43..acd09f8df79 100644
--- a/src/mongo/bson/mutable/document.cpp
+++ b/src/mongo/bson/mutable/document.cpp
@@ -1898,6 +1898,30 @@ namespace mutablebson {
         }
     }
 
+    Status Element::setValueElement(ConstElement setFrom) {
+        verify(ok());
+
+        // Can't set to your own root element, since this would create a circular document.
+        if (_doc->root() == setFrom) {
+            return Status(ErrorCodes::IllegalOperation,
+                          "Attempt to set an element to its own document's root");
+        }
+
+        // Setting to self is a no-op.
+        //
+        // Setting the root is always an error so we want to fall through to the error handling in
+        // this case.
+        if (*this == setFrom && _repIdx != kRootRepIdx) {
+            return Status::OK();
+        }
+
+        Document::Impl& impl = getDocument().getImpl();
+        ElementRep thisRep = impl.getElementRep(_repIdx);
+        const StringData fieldName = impl.getFieldNameForNewElement(thisRep);
+        Element newValue = getDocument().makeElementWithNewFieldName(fieldName, setFrom);
+        return setValue(newValue._repIdx);
+    }
+
     BSONType Element::getType() const {
         verify(ok());
         const Document::Impl& impl = getDocument().getImpl();