DeviceType._abs_weight being stored as float value though it is a PositiveBigIntegerField

[bctiemann]

Deployment Type

Self-hosted

Triage priority

I volunteer to perform this work (if approved)

NetBox Version

v4.1.6

Python Version

3.11

Steps to Reproduce

It is possible to store a non-integer value in WeighMixin._abs_weight fields (which are PositiveBigIntegerField) prior to the object being persisted to the database. This potentially causes deserialization errors when populating a new object via a core serializer which uses the field's to_python method.

Expected Behavior

The value of DeviceType._abs_weight should be the same (an integer value) both before and after persistence and refresh from the DB.

Observed Behavior

In [9]: dt.weight = 10.234567

In [10]: dt.save()

In [11]: dt._abs_weight
Out[11]: 10.234567

In [12]: dt.refresh_from_db()

In [13]: dt._abs_weight
Out[13]: 10

As we see here, a DeviceType object populated with a non-integer weight will have that non-integer value assigned to _abs_weight until the object is persisted to the database and refreshed. If, however, the DeviceType object is populated with data and not refreshed from the DB before it is used in another operation (such as deserialization into another DeviceType object), a DeserializationError is raised from the field's to_python code which expects an integer but receives a float.

The cause is this code:

    def save(self, *args, **kwargs):

        # Store the given weight (if any) in grams for use in database ordering
        if self.weight and self.weight_unit:
            self._abs_weight = to_grams(self.weight, self.weight_unit)
        else:
            self._abs_weight = None

        super().save(*args, **kwargs)

The output of to_grams should be coerced to an int before being assigned to self._abs_weight.

Note: Moved from netboxlabs/netbox-branching#162