Pickling objects that contain umongo documents.

[jbkoh]

Hi there,

Thanks for the great project! I'm trying to replace mongoengine with umongo because of its awesome asyncio support. In that, I got a problem. I'd really appreciate any input here:

I'm trying to dump objects that contain umongo documents. I put an MRE here:

import pickle
import cloudpickle
import asyncio

from umongo import Document
from umongo.fields import StringField
from umongo import MotorAsyncIOInstance
from motor.motor_asyncio import AsyncIOMotorClient

instance = MotorAsyncIOInstance()

async def setup_mongo():
    db_name = 'testdb'
    mongourl = f"mongodb://localhost:27017/{db_name}"
    loop = asyncio.get_event_loop()
    conn = AsyncIOMotorClient(mongourl, io_loop=loop)
    db = conn.get_database(db_name)
    instance.init(db)

@instance.register
class TestDoc(Document):
    test_field = StringField()

async def ensure_indexes():
    await TestDoc.ensure_indexes()


class TestClass(object):
    def __init__(self, test_model):
        self.test_model = test_model
        self.test_data = 'abcd'

async def main():
    await setup_mongo()
    await ensure_indexes()

    test_doc = TestDoc(test_field= '1234')
    test_instance = TestClass(test_model=test_doc)
    print(pickle.dumps(test_instance))

if __name__ == '__main__':
    asyncio.run(main())

However, this says:

  File "test.py", line 39, in main
    print(pickle.dumps(test_instance))
_pickle.PicklingError: Can't pickle <class 'umongo.data_proxy.TestDocDataProxy'>: attribute lookup TestDocDataProxy on umongo.data_proxy failed

I also checked #167 saying that umongo has its own way of dumping and loading and pickling won't work. What would be the best way of resolving the above case?

Thanks in advance.