1 files changed, 36 insertions, 0 deletions
diff --git a/jstests/aggregation/sources/setWindowFields/range_wrong_type.js b/jstests/aggregation/sources/setWindowFields/range_wrong_type.js
new file mode 100644
index 00000000000..26001c40888
--- /dev/null
+++ b/jstests/aggregation/sources/setWindowFields/range_wrong_type.js
@@ -0,0 +1,36 @@
+/**
+ * Test that a window of the form [+N, unbounded] does not trigger a tassert
+ * on mixed-type input.
+ *
+ * Originally intended to reproduce SERVER-71387.
+ */
+(function() {
+"use strict";
+
+const coll = db.set_window_fields_range_wrong_type;
+coll.drop();
+assert.commandWorked(coll.insert([
+    // Numbers sort before strings, so we'll scan {a: 2} first.
+    {a: 2},
+    {a: 'xyz'},
+]));
+
+const err = assert.throws(() => {
+    return coll
+        .aggregate({
+            $setWindowFields: {
+                sortBy: {a: 1},
+                output: {
+                    // The lower bound +3 excludes the current document {a: 2}.
+                    // The only remaining document is {a: 'xyz'}.
+                    // We wrongly consider {a: 'xyz'} to be 'within' the lower bound.
+                    // Then, when we search for the upper bound, we are surprised
+                    // to be starting from 'xyz' which is the wrong type.
+                    b: {$max: 5, window: {range: [+3, 'unbounded']}},
+                },
+            }
+        })
+        .toArray();
+});
+assert.eq(err.code, 5429414, err);
+})();