Config Render crashes netbox

[ITTV-tools]

Deployment Type

Self-hosted

Triage priority

I volunteer to perform this work (if approved)

NetBox Version

4.2.1

Python Version

3.12

Steps to Reproduce

Create an device with an template

{% for interface in device.interfaces.all() %}
{%- if interface.mgmt_only == false %}
interface {{ interface.name }}
{%- if interface.description %}
description {{interface.description}}
{%- endif%}
{%- if interface.enabled == false %}
shutdown 
{%- elif interface.enabled == true %} 
no shutdown 
{%- endif%}
{%- if not interface.name.startswith('Vlan') %} 
{%- if interface.mode == "access" %}
switchport mode access
switchport nonegotiate
snmp trap mac-notification change added
snmp trap mac-notification change removed
{%- if device.dot1x %}
access-session control-direction in
access-session closed
access-session port-control auto
dot1x pae authenticator
service-policy type control subscriber POLICY_Access-Interfaces
{%- endif %}
{%- if interface.untagged_vlan %}
switchport access vlan {{ interface.untagged_vlan.vid }}
{%- endif %}
spanning-tree portfast
spanning-tree guard root
{%- elif interface.mode == "tagged" %} 
switchport mode trunk
switchport nonegotiate 
{%- if interface.untagged_vlan %}
switchport trunk nativ vlan {{ interface.untagged_vlan.vid }}
{%- endif %}
{%- for vlan in interface.tagged_vlans.all() %} 
switchport trunk allowed vlan add {{vlan.vid }} 
{%- endfor %} 
{%- elif "tagged-all" in interface.mode %}
{%- if "Access Point" in interface.tags.names() %}
snmp trap mac-notification change added
snmp trap mac-notification change removed
{%- endif %}
switchport mode trunk
switchport nonegotiate 
switchport trunk allowed vlan all
{%- if interface.untagged_vlan %}
switchport trunk nativ vlan {{ interface.untagged_vlan.vid }}
{%- endif %} 
{%- else %} 
{%-if interface.lag != None %} 
channel-group {% for char in interface.lag.name %}{%- if char.isdigit() %}{{ char }}{%- endif %}
{%-endfor %} mode on
{%- endif%} 
{%- endif %} 
{%- endif %}
{%- endif %} 
{%- if interface.ip_addresses.all() %}
{%- for ip in interface.ip_addresses.all() %}
ip address {{ ip.address.ip}} {{ ip.address.netmask }}
{%- endfor %}
 no ip route-cache
{%- endif %}
!
{%- endfor %}

Expected Behavior

Config should render, as it has in version: 4.1.7

Observed Behavior

Netbox crashes:

TypeError at /dcim/devices/55/render-config/

argument of type 'NoneType' is not iterable

Request Method:	GET
http:///dcim/devices/55/render-config/
5.1.4
TypeError
argument of type 'NoneType' is not iterable
, line 226, in top-level template code		dcim.views.DeviceRenderConfigView		/opt/netbox/venv/bin/python		3.12.3		['/opt/netbox/netbox/', '/usr/lib/python312.zip', '/usr/lib/python3.12', '/usr/lib/python3.12/lib-dynload', '/opt/netbox/venv/lib/python3.12/site-packages']		Thu, 16 Jan 2025 10:02:34 +0000

[DanSheps]

So it does appear the reverse manager is not being set. This is likely an undocumented upstream change but I am not 100% sure. Still looking into it.

[jeremystretch]

@ITTV-tools please reduce the example template to the minimum amount of logic required to reproduce the bug. This will ease troubleshooting efforts.