aggregation query broken after upgrade to Mongo 3.6.2

[thumbert]

Hi,

I have an example of a simple aggregation that is no longer working after upgrading mongodb from version 3.4 to 3.6.2. Here is the error:

00:00 +0: mongo 3.6.2 bug check data
00:00 +1: mongo 3.6.2 bug find max date
00:00 +1 -1: mongo 3.6.2 bug find max date [E]
{ok: 0.0, errmsg: The 'cursor' option is required, except for aggregate with the explain argument, code: 9, codeName: FailedToParse}
dart:async/future_impl.dart 22 _Completer.completeError
package:mongo_dart/src/database/db.dart 281:14 Db.executeDbCommand
===== asynchronous gap ===========================

I add a test file. Thank you for taking a look. The query runs fine in the mongo shell.

Best regards

import 'package:mongo_dart/mongo_dart.dart';
import 'package:test/test.dart';

aggTest() async {
group('mongo 3.6.2 bug', (){
List data = [
{'type': 'A', 'date': '2017-01-01'},
{'type': 'AA', 'date': '2017-01-01'},
{'type': 'B', 'date': '2017-01-02'},
{'type': 'D', 'date': '2017-01-04'},
{'type': 'C', 'date': '2017-01-03'},
];

Db db = new Db('mongodb://127.0.0.1/test');
DbCollection coll = db.collection("agg_bug");

setUp(() async {
  await db.open();
  await coll.insertAll(data);
});
tearDown(() async {
  await coll.remove();
  await db.close();
});
test('check data', () async {
  var res = await coll.count();
  expect(res, 5);
});
test('find max date', () async {
  List pipeline = [];
  pipeline.add({'\$group': {
    '_id': 0,
    'lastDay': {'\$max': '\$date'}}});
  Map res = await coll.aggregate(pipeline);
  var lastDay = res['result'][0]['lastDay'];
  expect(lastDay, '2017-01-04');
});

});
}

main() async {
await aggTest();
}

[thosakwe]

https://pub.dartlang.org/packages/mongo_dart/versions/0.3.4