Fix: TypeError: ObjectId is not JSON serializable: A Flask JSONEncoder for Mongoengine documents. Specifically useful for use with Flask-Mongoengine.

mongoengine_jsonencoder.py

from flask import Flask
from flask.json import JSONEncoder
from bson import json_util
from mongoengine.base import BaseDocument
from mongoengine.queryset.base import BaseQuerySet

class MongoEngineJSONEncoder(JSONEncoder):
    def default(self,obj):
        if isinstance(obj,BaseDocument):
            return json_util._json_convert(obj.to_mongo())
        elif isinstance(obj,BaseQuerySet):
            return json_util._json_convert(obj.as_pymongo())
        return JSONEncoder.default(self, obj)

'''
To use:
from mongoengine_jsonencoder import MongoEngineJsonEncoder
app = Flask(__name__)
app.json_encoder = MongoEngineJSONEncoder

Now Flask's jsonify works for Mongoengine querysets, and documents.
'''

Thank you that saved me!

from bson.objectid import ObjectId
from core.services.db_connection import DbConnectionService

class DbExecutionService:
     def __init__(self):
        self.db = DbConnectionService()

     def list(self, collection, search):
        session = self.db.create_connection(collection)
        return list(map(lambda row: {i: str(row[i]) if isinstance(row[i], ObjectId) else row[i] for i in row}, session.find(search))