Updating a GFK field via API does not return the new value

[amhn]

NetBox version

v3.4.8

Python version

3.10

Steps to Reproduce

1. Create IP-Address (do not assign object)
2. Create Object to assign (e.g. FHRP Group
3. curl -H "Authorization: Token $NETBOX_TOKEN" -H "Content-type: application/json" $NETBOX_SCHEME://$NETBOX_URL/api/ipam/ip-addresses/1/ -X PATCH --data '{"assigned_object_type": "ipam.fhrpgroup", "assigned_object_id":1}'

Expected Behavior

assigned_object in the response is not null.

Observed Behavior

assigned_object is null:

{
    "id": 1,
    "url": "http://localhost:8000/api/ipam/ip-addresses/1/",
    "display": "127.0.0.1/32",
    "family": {
        "value": 4,
        "label": "IPv4"
    },
    "address": "127.0.0.1/32",
    "vrf": null,
    "tenant": null,
    "status": {
        "value": "active",
        "label": "Active"
    },
    "role": null,
    "assigned_object_type": "ipam.fhrpgroup",
    "assigned_object_id": 1,
    "assigned_object": null,
    "nat_inside": null,
    "nat_outside": [],
    "dns_name": "",
    "description": "",
    "comments": "",
    "tags": [],
    "custom_fields": {},
    "created": "2023-04-23T09:32:24.766755Z",
    "last_updated": "2023-04-23T09:35:09.908879Z"
}

This is only the case if the assigned_object was not assigned before the request. Changing or removing the assigned object gives the correct response.

[arthanson]

Potentially a bug in DRF / Django? we aren't doing anything special and it should be getting auto-updated, possibly related to using non-default names for the GFK fields as there have been bugs in Django related to that previously. I'll need to test it with a small sample program.

[amhn]

See my previous comment #10221 (comment) to #10221

Instead of only checking if the object exists, the patch in #11550 should have assigned it to the assigned_object field. I think.

The problem seems to be that None is None and not a None of type GFK. Once there is an object assigned to a GFK the auto update works.

[arthanson]

Thanks for that, checking...