Unexpected error in aggregation $multiply

[shai-katzir-hs]

issue

Getting an AssertionError on a $multiply aggregation, which is not compatible with pymongo

Aggregation:

collection.aggregate([
        {"$match": {'some_id': 1}},
        {'$project': {'_id': {'some_id': 'some_id'}, 'max_score': {'$multiply': [bson.Decimal128("34"), 8]}}}
    ])

Exception:

AssertionError: $multiply only uses numbers

reproduce

import datetime
import mongomock
import bson
import pymongo
import pytest

@pytest.mark.parametrize("name,db", [('pymongo', pymongo.MongoClient().db),  ('mongomock',mongomock.MongoClient().db)])
def test_increase_votes_pymongo(name, db):
    collection = db['collection']
    collection.insert_one({
        'date_applied': datetime.datetime.now(tz=datetime.timezone.utc),
        'some_id': 1
    })
    print(list(collection.aggregate([
        {"$match": {'some_id': 1}},
        {'$project': {'_id': {'some_id': 'some_id'}, 'max_score': {'$multiply': [bson.Decimal128("34"), 8]}}}
    ])))

will fail on MongoMock only

additional info

versions:
pymongo==4.6.1 mongomock==4.1.2