I'm getting an error while using Flask_JWT with Mongoengine 'dict' object has no attribute 'id'

My User Model looks like this

class UserModel(Document):
    first_name = StringField(required=True, max_length=50)
    last_name = StringField(required=True, max_length=50)
    username = StringField(required=True)
    password = StringField(required=True, min_length=6)

def to_json(self):
    return {
            "id": str(self.pk),
            "first_name": self.first_name,
            "last_name": self.last_name,
            "username": self.username,
            "password": self.password
        }

My authentication methods look like this

def authenticate(username, password):
    user = UserModel.objects.get(username=username)
    if user and checkpw(password.encode('utf-8'), user.password.encode('utf-8')):
    return user.to_json()

def identity(payload):
    user_id = payload['identity']
    u = UserModel.objects.get(pk=user_id)
    return u.to_json


jwt = JWT(app, authenticate, identity)  # /auth endpoint

I created the to_json() method hoping to solve this issue and to serialize the primary key which will appear in a normal query like this

"_id" : ObjectId("5aa9613d4fe35c23fca4d601")
instead of nicely like this~
"id": "5aa9613d4fe35c23fca4d601"

The error I get is:

  "/home/joe/PyRest/FlaskMongo-venv/lib/python3.6/site-packages/flask_jwt/__init__.py", line 53, in _default_jwt_payload_handler
    identity = getattr(identity, 'id') or identity['id']
AttributeError: 'dict' object has no attribute 'id'`

This is a common complaint for Flask-JWT. At a glance it looks like it has 7 open merge requests to fix it: https://github.com/mattupstate/flask-jwt/pulls?utf8=%E2%9C%93&q=is%3Apr+is%3Aopen+id

Unfortunately flask-jwt has been abandoned for a long time now. Perhaps check out flask-jwt-extended or flask-jwt-simple as alternatives that are still actively maintained (and IMO better designed, but I am the author so I am of course biased) ;)