Missing change log entries for updated many-to-many fields as part of deletes

[fabi125]

NetBox version

v3.6.4

Python version

3.8

Steps to Reproduce

1. Create a couple of device roles and a config context that is assigned to those two roles:

{
    "id": 1,
    "url": "https://demo.netbox.dev/api/extras/config-contexts/1/",
    "display": "Test Context",
    "name": "Test Context",
    "weight": 1000,
    "description": "",
    "is_active": true,
    "regions": [],
    "site_groups": [],
    "sites": [],
    "locations": [],
    "device_types": [],
    "roles": [
        {
            "id": 13,
            "url": "https://demo.netbox.dev/api/dcim/device-roles/13/",
            "display": "Test Role",
            "name": "Test Role",
            "slug": "test-role"
        },
        {
            "id": 14,
            "url": "https://demo.netbox.dev/api/dcim/device-roles/14/",
            "display": "Test Role 2",
            "name": "Test Role 2",
            "slug": "test-role-2"
        }
    ],
    "platforms": [],
    "cluster_types": [],
    "cluster_groups": [],
    "clusters": [],
    "tenant_groups": [],
    "tenants": [],
    "tags": [],
    "data_source": null,
    "data_path": "",
    "data_file": null,
    "data_synced": null,
    "data": {
        "foo": 123
    },
    "created": "2023-10-18T22:07:46.872083Z",
    "last_updated": "2023-10-18T22:07:46.872120Z"
}

2. Delete one of the roles

Expected Behavior

This should result in two change log entries: one for the device role deletion and one for the update to the config context.

Observed Behavior

Only a single change log entry is created:

GET /api/extras/object-changes/?request_id=8f69edb2-918f-40da-ac13-2fd1b8d5a3e6

{
    "count": 1,
    "next": null,
    "previous": null,
    "results": [
        {
            "id": 5179,
            "url": "https://demo.netbox.dev/api/extras/object-changes/5179/",
            "display": "dcim | device role Test Role deleted by admin",
            "time": "2023-10-18T22:08:46.787241Z",
            "user": {
                "id": 54,
                "url": "https://demo.netbox.dev/api/users/users/54/",
                "display": "admin",
                "username": "admin"
            },
            "user_name": "admin",
            "request_id": "8f69edb2-918f-40da-ac13-2fd1b8d5a3e6",
            "action": {
                "value": "delete",
                "label": "Deleted"
            },
            "changed_object_type": "dcim.devicerole",
            "changed_object_id": 13,
            "changed_object": null,
            "prechange_data": {
                "name": "Test Role",
                "slug": "test-role",
                "tags": [],
                "color": "9e9e9e",
                "created": "2023-10-18T22:07:13.945Z",
                "vm_role": true,
                "description": "",
                "last_updated": "2023-10-18T22:07:13.945Z",
                "custom_fields": {},
                "config_template": null
            },
            "postchange_data": null
        }
    ]
}

But the config context is updated:

{
    "id": 1,
    "url": "https://demo.netbox.dev/api/extras/config-contexts/1/",
    "display": "Test Context",
    "name": "Test Context",
    "weight": 1000,
    "description": "",
    "is_active": true,
    "regions": [],
    "site_groups": [],
    "sites": [],
    "locations": [],
    "device_types": [],
    "roles": [
        {
            "id": 14,
            "url": "https://demo.netbox.dev/api/dcim/device-roles/14/",
            "display": "Test Role 2",
            "name": "Test Role 2",
            "slug": "test-role-2"
        }
    ],
    "platforms": [],
    "cluster_types": [],
    "cluster_groups": [],
    "clusters": [],
    "tenant_groups": [],
    "tenants": [],
    "tags": [],
    "data_source": null,
    "data_path": "",
    "data_file": null,
    "data_synced": null,
    "data": {
        "foo": 123
    },
    "created": "2023-10-18T22:07:46.872083Z",
    "last_updated": "2023-10-18T22:07:46.872120Z"
}

Note: I believe this affects all models that use ManyToManyField relations.

[jeremystretch]

I believe this would be addressed by FR #14059.

[fabi125]

I believe this would be addressed by FR #14059.

Ah yes! I tried to search for open issues, but couldn't find anything. Great timing how you just opened it 2 days ago :)

[fabi125]

Note: I also found this 12 year old Django bug that seems related: https://code.djangoproject.com/ticket/17688
So the easiest way for NetBox to fix this, is probably #14059.

[jeremystretch]

It may be some time before we can tackle #14059 (assuming it's even feasible), so let's see if we can come with a fix in the interim.