Dynamic Group issues after object modification

[mzbroch]

Environment

• Nautobot version (Docker tag too if applicable): 1.5.16
• Python version:
• Database platform, version:
• Middleware(s):

Steps to Reproduce

1. Create two Platform objects:

- name: juniper_junos
  slug: juniper_junos
- name: cisco_ios
  slug: cisco_ios

2. Create dynamic group for Device object , in a Platform field select two created platforms.

3. Modify Platform slug and name: change cisco_ios to cisco-ios (dash instead of underscore)

4. Attempt to modify dynamic group

5. After modifying Platform, cisco-ios is now not visible in a form.

Expected Behavior

Clicking "Update" button results in modifying the dynamic group.

Observed Behavior

Clicking "Update" button and saving dynamic group results with an error:

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[glennmatthews]

Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/django/forms/models.py", line 413, in _post_clean
    self.instance.full_clean(exclude=exclude, validate_unique=False)
  File "/usr/local/lib/python3.10/site-packages/django/db/models/base.py", line 1251, in full_clean
    raise ValidationError(errors)

During handling of the above exception ({'platform': ['Select a valid choice. cisco-ios is not one of the available choices.']}), another exception occurred:
  File "/usr/local/lib/python3.10/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.10/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/views/generic/base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "/source/nautobot/core/views/generic.py", line 419, in dispatch
    return super().dispatch(request, *args, **kwargs)
  File "/source/nautobot/utilities/views.py", line 114, in dispatch
    return super().dispatch(request, *args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/views/generic/base.py", line 98, in dispatch
    return handler(request, *args, **kwargs)
  File "/source/nautobot/extras/views.py", line 616, in post
    if form.is_valid():
  File "/usr/local/lib/python3.10/site-packages/django/forms/forms.py", line 175, in is_valid
    return self.is_bound and not self.errors
  File "/usr/local/lib/python3.10/site-packages/django/forms/forms.py", line 170, in errors
    self.full_clean()
  File "/usr/local/lib/python3.10/site-packages/django/forms/forms.py", line 374, in full_clean
    self._post_clean()
  File "/usr/local/lib/python3.10/site-packages/django/forms/models.py", line 415, in _post_clean
    self._update_errors(e)
  File "/usr/local/lib/python3.10/site-packages/django/forms/models.py", line 389, in _update_errors
    self.add_error(None, errors)
  File "/usr/local/lib/python3.10/site-packages/django/forms/forms.py", line 343, in add_error
    raise ValueError(

Exception Type: ValueError at /extras/dynamic-groups/test/edit/
Exception Value: 'DynamicGroupForm' has no field named 'platform'.

[glennmatthews]

For context, DynamicGroup updates via the UI are done through multiple forms rather than a single unified form class - DynamicGroupForm only understands/validates/updates the base class attribute (name, content_type, etc.) while the filter is updated via a form dynamically constructed by instance.generate_filter_form(). The issue here is that because the underlying data changed, the existing DynamicGroup instance's filter data is no longer valid (in this specific case it references a slug that no longer exists, but the same issue would happen for e.g. a UUID-based filter that referenced a now-deleted object), and so when the DynamicGroupForm.is_valid() is called, calling the instance.full_clean() fails before the generated "filter_form" has a chance to update the instance to a new (valid) filter value.

Most likely the required fix here will be to change the form definitions and/or code flow in DynamicGroupEditView.post() so that there's only a single form class/object that handles the updating/validation of the entire DynamicGroup instance data in a single pass. This will be pretty invasive code-wise but I think it's necessary.

Changing the model clean/clean_fields/full_clean logic turned out to be a cleaner way to accomplish this specific fix.