SERVER-8088: $unwind of scalar should return 1 doc with scalar

1 files changed, 12 insertions, 8 deletions

diff --git a/src/mongo/db/pipeline/document_source_unwind.cpp b/src/mongo/db/pipeline/document_source_unwind.cpp
index 11c8d0880ec..2caf7f95c64 100644
--- a/src/mongo/db/pipeline/document_source_unwind.cpp
+++ b/src/mongo/db/pipeline/document_source_unwind.cpp
@@ -87,17 +87,11 @@ namespace mongo {
             return;
         }
 
-        // The target field must be an array to unwind.
-        uassert(15978, str::stream() << "Value at end of $unwind field path '"
-                << _unwindPath.getPath(true) << "' must be an Array, but is a "
-                << typeName(pathValue.getType()),
-                pathValue.getType() == Array);
-
         _inputArray = pathValue;
     }
 
     boost::optional<Document> DocumentSourceUnwind::Unwinder::getNext() {
-        if (_inputArray.missing() || _index == _inputArray.getArrayLength())
+        if (_inputArray.missing())
             return boost::none;
 
         // If needed, this will automatically clone all the documents along the
@@ -107,7 +101,17 @@ namespace mongo {
         // along the path leading to that will be replaced in order not to share
         // that change with any other clones (or the original).
 
-        _output.setNestedField(_unwindPathFieldIndexes, _inputArray[_index]);
+        if (_inputArray.getType() == Array) {
+            if (_index == _inputArray.getArrayLength())
+                return boost::none;
+            _output.setNestedField(_unwindPathFieldIndexes, _inputArray[_index]);
+        }
+        else if (_index > 0) {
+            return boost::none;
+        }
+        else {
+            //_output.setNestedField(_unwindPathFieldIndexes, _inputArray);
+        }
         _index++;
         return _output.peek();
     }