1 files changed, 28 insertions, 1 deletions
diff --git a/src/mongo/db/pipeline/document_source_bucket_test.cpp b/src/mongo/db/pipeline/document_source_bucket_test.cpp
index 1036c456ef3..e7702d58d28 100644
--- a/src/mongo/db/pipeline/document_source_bucket_test.cpp
+++ b/src/mongo/db/pipeline/document_source_bucket_test.cpp
@@ -79,7 +79,8 @@ public:
 
         // Serialize the DocumentSourceGroup and DocumentSourceSort from $bucket so that we can
         // check the explain output to make sure $group and $sort have the correct fields.
-        auto explain = ExplainOptions::Verbosity::kQueryPlanner;
+        auto explain =
+            SerializationOptions{boost::make_optional(ExplainOptions::Verbosity::kQueryPlanner)};
         vector<Value> explainedStages;
         groupStage->serializeToArray(explainedStages, explain);
         sortStage->serializeToArray(explainedStages, explain);
@@ -227,9 +228,35 @@ TEST_F(BucketReturnsGroupAndSort, BucketSucceedsWithMultipleBoundaryValues) {
     testCreateFromBsonResult(spec, expectedGroupExplain);
 }
 
+TEST_F(BucketReturnsGroupAndSort, BucketWithEmptyGroupByStrDoesNotAccessPastEndOfString) {
+    // Verify that {groupBy: ''} is rejected _without_ attempting to read past the end of the empty
+    // string.
+    const auto spec =
+        fromjson("{$bucket : {groupBy : '', boundaries : [ 1, 5, 8 ], default : 'other'}}");
+
+    // Under a debug build, this would previously fail if an empty str for groupBy led to access
+    // past the end of the string, with pos() > size() in StringData::operator[].
+    // Verify that this reaches the intended uassert, rejecting the empty string, _without_ first
+    // trying to read past the end of the string.
+    ASSERT_THROWS_CODE(DocumentSourceBucket::createFromBson(spec.firstElement(), getExpCtx()),
+                       AssertionException,
+                       40202);
+}
+
+/*
+ * Override the stub interface to allow full execution in these tests.
+ */
+class ExecutableStubMongoProcessInterface : public StubMongoProcessInterface {
+    bool isExpectedToExecuteQueries() override {
+        return true;
+    }
+};
+
 class InvalidBucketSpec : public AggregationContextFixture {
 public:
     list<intrusive_ptr<DocumentSource>> createBucket(BSONObj bucketSpec) {
+        getExpCtx()->mongoProcessInterface =
+            std::make_unique<ExecutableStubMongoProcessInterface>();
         auto sources = DocumentSourceBucket::createFromBson(bucketSpec.firstElement(), getExpCtx());
         return sources;
     }