CODEWITHSUNDEEP
pythonflaskmongoengineflask-restfulflask-mongoengine
JacquesJ
JacquesJ

Reputation: 22

Flask Mongoengine ValidationError Field is required on .save() but fields already exist in db

Problem: I get a ValidationError when trying to perform a .save() when appending a value to an EmbeddedDocumentListField because I am missing required fields that already exist on the document.

Note that at this point the User document has already been created as part of the signup process, so it already has an email and password in the DB.

My classes:

class User(gj.Document):
    email = db.EmailField(required=True, unique=True)
    password = db.StringField(required=True)
    long_list_of_thing_1s = db.EmbeddedDocumentListField("Thing1")
    long_list_of_thing_2s = db.EmbeddedDocumentListField("Thing2")

class Thing1(gj.EmbeddedDocument):
    some_string = db.StringField()

class Thing2(gj.EmbeddedDocument):
    some_string = db.StringField()

Trying to append a new EmbeddedDocument to the EmbeddedDocumentListField in my User class in the Thing2 Resource endpoint:

class Thing2(Resource):
    def post(self):
        try:
            body = request.get_json()
            user_id = body["user_id"]

            user = UserModel.objects.only("long_list_of_thing_2s").get(id=user_id)

            some_string = body["some_string"]

            new_thing_2 = Thing2Model()
            new_thing_2.some_string = some_string
        
            user.long_list_of_thing_2s.append(new_thing_2)
            user.save()

            return 201
        except Exception as exception:
            raise InternalServerError

On hitting this endpoint I get the following error on the user.save()

mongoengine.errors.ValidationError: ValidationError (User:603e39e7097f3e9a6829f422) (Field is required: ['email', 'password'])

I think this is because of the .only("long_list_of_thing_2s")

But I am specifically using UserModel.objects.only("long_list_of_thing_2s") because I don't want to be inefficient in bringing the entire UserModel into memory when I only want to append something the long_list_of_thing_2s

Is there a different way I should be going about this? I am relatively new to Flask and Mongoengine so I am not sure what all the best practices are when going about this process.

Upvotes: 0

Views: 625

Answers (1)

bagerard
bagerard

Reputation: 6354

You are correct, this is due to the .only and is a known "bug" in MongoEngine. Unless your Model is really large, using .only() will not make a big difference so I'd recommend to use it only if you observe performance issues.

If you do have to keep the .only() for whatever reason, you should be able to make use of the push atomic operator. An advantage of using the push operator is that in case of race conditions (concurrent requests), it will gracefully deal with the different updates, this is not the case with regular .save() which will overwrite the list.

Upvotes: 1

Related Questions