Changes API returns 500 when branch with cable deletion is active

[clovehitch]

Plugin Version

0.8.2

NetBox Version

Reproduced on 4.4.10 and 4.5.5

Python Version

3.12.3

Steps to Reproduce

Steps to Reproduce:

1. Create a cable between two physical interfaces on main
2. Create and provision a branch
3. Delete the cable within the branch (using X-NetBox-Branch header)
4. Query GET /api/plugins/branching/changes/?branch_id= with the X-NetBox-Branch header still set

Expected Behavior

The changes API returns the list of branch changes including the cable deletion, interface updates, and cable termination changes.

Observed Behavior

Observed Behavior: Returns HTTP 500:
{
"error": "Cable matching query does not exist.",
"exception": "DoesNotExist",
"netbox_version": "4.5.5",
"python_version": "3.12.3"
}

Removing the X-NetBox-Branch header and querying with only the branch_id parameter returns results correctly.

[jnovinger]

Root cause seems to be in ChangeDiffSerializer.get_object() (api/serializers.py around line 130). When the branch is active, obj.object resolves the GenericForeignKey via the branch schema. If the referenced object was deleted in the branch, that lookup raises DoesNotExist instead of returning None. The serializer already handles SerializerNotFound but not this case.

[jnovinger]

Removing the X-NetBox-Branch header and querying with only the branch_id parameter returns results correctly.

While it's true that removing the header does result in a 200 with data, it's not going to show you the state of the object in the branch. I wouldn't rely on this as a workaround.