Add Device runs into Server Error

[doc-slice]

In a filled netbox instance with a lot of locations, racks, devices and cables i run into a server error while adding a device. To reproduce the error, I setup a new netbox instance with a new database. There is only one site, one manufacturer, one device type and one device role. If I now want to create a device, I get this error:

Server Error
There was a problem with your request. Please contact an administrator.

The complete exception is provided below:

<class 'TypeError'>

object of type 'NoneType' has no len()

Python version: 3.11.5
NetBox version: 3.7.1
Plugins: None installed

What is going wrong here? How can I analyze and fix the problem?

[candlerb]

How can I analyze and fix the problem?

Please generate a full Python backtrace and post it here.

The best way is to set EMAIL and ADMINS in configuration.py; in this case, if an exception ever occurs in production, it will be mailed to the admins. Alternatively, you can set DEBUG=True in configuration.py, in which case the exception will be displayed in the web browser (but only do this in dev environments, or temporarily in production)

[doc-slice]

To analyse the error, I set up an empty netbox instance. Here is the output in debug mode:

Environment:

Request Method: POST
Request URL: https://ip-01.igms.lan/dcim/devices/add/

Django Version: 4.2.9
Python Version: 3.11.5
Installed Applications:
['django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'django.contrib.humanize',
'django.forms',
'corsheaders',
'debug_toolbar',
'graphiql_debug_toolbar',
'django_filters',
'django_tables2',
'django_prometheus',
'graphene_django',
'mptt',
'rest_framework',
'social_django',
'taggit',
'timezone_field',
'core',
'account',
'circuits',
'dcim',
'ipam',
'extras',
'tenancy',
'users',
'utilities',
'virtualization',
'vpn',
'wireless',
'django_rq',
'drf_spectacular',
'drf_spectacular_sidecar']
Installed Middleware:
['graphiql_debug_toolbar.middleware.DebugToolbarMiddleware',
'django_prometheus.middleware.PrometheusBeforeMiddleware',
'corsheaders.middleware.CorsMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware',
'django.middleware.security.SecurityMiddleware',
'netbox.middleware.RemoteUserMiddleware',
'netbox.middleware.CoreMiddleware',
'netbox.middleware.MaintenanceModeMiddleware',
'django_prometheus.middleware.PrometheusAfterMiddleware']

Traceback (most recent call last):
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/core/handlers/exception.py", line 55, in inner
response = get_response(request)
^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/core/handlers/base.py", line 197, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/views/generic/base.py", line 104, in view
return self.dispatch(request, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/netbox/views/generic/object_views.py", line 172, in dispatch
return super().dispatch(request, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/netbox/views/generic/base.py", line 26, in dispatch
return super().dispatch(request, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/utilities/views.py", line 99, in dispatch
return super().dispatch(request, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/views/generic/base.py", line 143, in dispatch
return handler(request, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/netbox/views/generic/object_views.py", line 260, in post
if form.is_valid():
^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/utilities/forms/mixins.py", line 55, in is_valid
is_valid = super().is_valid()
^^^^^^^^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/forms/forms.py", line 201, in is_valid
return self.is_bound and not self.errors
^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/forms/forms.py", line 196, in errors
self.full_clean()
^^^^^^^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/forms/forms.py", line 435, in full_clean
self._post_clean()
^^^^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/netbox/forms/base.py", line 69, in _post_clean
return super()._post_clean()
^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/forms/models.py", line 486, in _post_clean
self.instance.full_clean(exclude=exclude, validate_unique=False)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/db/models/base.py", line 1477, in full_clean
self.clean()
^^^^^^^^^^^^
File "/opt/netbox/netbox/dcim/models/devices.py", line 833, in clean
super().clean()
^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/extras/models/configs.py", line 200, in clean
super().clean()
^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/netbox/models/init.py", line 71, in clean
super().clean()
^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/netbox/models/features.py", line 268, in clean
super().clean()
^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/netbox/models/features.py", line 313, in clean
post_clean.send(sender=self.class, instance=self)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/dispatch/dispatcher.py", line 176, in send
return [

File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/dispatch/dispatcher.py", line 177, in
(receiver, receiver(signal=self, sender=sender, **named))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/extras/signals.py", line 208, in run_save_validators
run_validators(instance, validators)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/extras/signals.py", line 200, in run_validators
validator(instance)
^^^^^^^^^^^^^^^^^^^
File "/opt/netbox/netbox/extras/validators.py", line 98, in call
validator(attr)
^^^^^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/core/validators.py", line 366, in call
cleaned = self.clean(value)
^^^^^^^^^^^^^^^^^
File "/opt/netbox-3.7.1/venv/lib64/python3.11/site-packages/django/core/validators.py", line 432, in clean
return len(x)
^^^^^^

Exception Type: TypeError at /dcim/devices/add/
Exception Value: object of type 'NoneType' has no len()

[candlerb]

Have you customized configuration.py - in particular, have you added any custom validators?

What values are you setting when you create your device: anything other than name, role, type, site and status?

[doc-slice]

Bull's eye! There is a custom validator for the asset tag field.
If I leave the asset tag field empty, I get the error. If I fill the asset tag field correctly, there is no error.
If I remove the custom validator from the configuration, there is also no more error.

Maybe the custom validator is not ok (I am not a regex specialist):

CUSTOM_VALIDATORS = {
"dcim.device": [
{
"asset_tag": {
"min_length": 15,
"max_length": 15,
"regex": '^\d{3}-\d{4}-\d{6}$'
}
}
]
}

Thanks for the quick help!