Reload doesn't check if attribute is writable

[xelhark]

Hello!

I noticed a weird behavior and managed to isolate the problem.

I think this situation is not as uncommon as it might appear:

from mongoengine import Document, IntField, connect

__author__ = 'gabriele'

connect('test_mongoengine')


class MyModel(Document):
    meta = {
        'strict': False
    }

    int_field = IntField()
    deleted_field = IntField()


new_model = MyModel(int_field=3, deleted_field=4)
new_model.save()


class MyModel(Document):
    int_field = IntField()

    meta = {
        'strict': False
    }

    @property
    def deleted_field(self):
        return 'default'


obj = MyModel.objects(int_field=3).first()

obj.reload()

This will cause mongoengine to raise an AttributeError :

[...]/mongoengine/base/document.py", line 187, in __setattr__
    super(BaseDocument, self).__setattr__(name, value)
AttributeError: can't set attribute

This is an inconsistent behavior because the error is NOT raised when the object is first loaded, but when it is reloaded.

[lafrech]

Duplicate of #1259?

[amcgregor]

@lafrech Related, but doesn't seem to be a duplicate. These are two very different problems, #1259 with reloading something that actually is still a field, this one the fact that the field attribute has been overridden with a non-field that can't be written to.

[amcgregor]

Looking into this a bit further, things are even stranger. After obj = MyModel.objects(int_field=3).first(), the following do give correct answers:

MyModel._fields
MyModel._fields_ordered
obj._fields
obj._fields_ordred

The reload code is inappropriately examining _data instead of the actual field lists to determine which attributes to save back out (to trigger the descriptor protocol on those fields).