SERVER-32300 Explainable.aggregate should not modify options argument.

Closes #1219
Signed-off-by: Charlie Swanson <charlie.swanson@mongodb.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/src/mongo/shell/explainable.js b/src/mongo/shell/explainable.js
index 795326ab9d0..67348a7e8e9 100644
--- a/src/mongo/shell/explainable.js
+++ b/src/mongo/shell/explainable.js
@@ -100,22 +100,22 @@ var Explainable = (function() {
             }
 
             // Add the explain option.
-            extraOpts = extraOpts || {};
+            let extraOptsCopy = Object.extend({}, (extraOpts || {}));
 
             // For compatibility with 3.4 and older versions, when the verbosity is "queryPlanner",
             // we use the explain option to the aggregate command. Otherwise we issue an explain
             // command wrapping the agg command, which is supported by newer versions of the server.
             if (this._verbosity === "queryPlanner") {
-                extraOpts.explain = true;
-                return this._collection.aggregate(pipeline, extraOpts);
+                extraOptsCopy.explain = true;
+                return this._collection.aggregate(pipeline, extraOptsCopy);
             } else {
                 // The aggregate command requires a cursor field.
-                if (!extraOpts.hasOwnProperty("cursor")) {
-                    extraOpts = Object.extend(extraOpts, {cursor: {}});
+                if (!extraOptsCopy.hasOwnProperty("cursor")) {
+                    extraOptsCopy = Object.extend(extraOptsCopy, {cursor: {}});
                 }
 
                 let aggCmd = Object.extend(
-                    {"aggregate": this._collection.getName(), "pipeline": pipeline}, extraOpts);
+                    {"aggregate": this._collection.getName(), "pipeline": pipeline}, extraOptsCopy);
                 let explainCmd = {"explain": aggCmd, "verbosity": this._verbosity};
                 let explainResult = this._collection.runReadCommand(explainCmd);
                 return throwOrReturn(explainResult);