Custom fields don't fully delete when using bulk delete

[joewesch]

Environment

• Python version: 3.7.13
• Nautobot version: 1.3.7b1

Steps to Reproduce

1. Create a custom field on a Device
2. Bulk delete the custom field

Expected Behavior

The CustomField object gets removed, but Device._custom_field_data still shows the custom field. It also shows up via GraphQL query.

Observed Behavior

The custom field should be removed from Device.

Analysis

When you delete an individual object in Nautobot, the ObjectDeleteView calls the .delete() method for that object. When you do a bulk delete, however, the BulkDeleteView creates a QuerySet of the items and calls QuerySet.delete().

There is a caveat of QuerySet.delete() from the documentation:

The delete() method does a bulk delete and does not call any delete() methods on your models.

In the case of CustomField there is a custom .delete() method that creates a Celery task to iterate through all of the objects that have that custom field and remove them accordingly. Since the CustomField.delete() method is not getting called, it is not cleaning the custom fields off of the related models. This is evident via the ORM or GraphQL.

In addition to CustomField, DeviceType also has a custom delete method, so they would also be susceptible to this same problem where the custom delete methods will not be called during the bulk delete.

Possible fixes

According to the documentation the QuerySet.delete() still emits a post_delete signal that can be used to run the custom delete actions instead.

[bryanculver]

@joewesch What's the use case for bulk-deleting custom fields?

[joewesch]

The use case I know of is when someone created multiple custom fields with dashes instead of underscores in the slugs. Since you can't edit a slug after creation they needed to delete the old custom fields and recreate them. Instead of going to each one individually and deleting them they did a bulk delete, which was easier/faster.