Adrien,
Your precise issue eludes me, but I have sometimes come across a similar issue
when changing the field types of models.
It appears that you still have a reference somewhere in your code between the
form and the model. I suspect that form.Form.ticket_description is a Django
default expected file name from one of your (original) CBV’s.
Alternative:
My method to resolve the Catch22 is to delete the most recent migration files,
including in your case, the migration file that originally created the
‘ticketdescription’ model. I move them to a dummy folder, in case they
shouldn’t have been deleted.
Bruckner de Villiers
083 625 1086
From: <django-users@googlegroups.com> on behalf of Adrien Agnel
<adrien.ag...@gmail.com>
Reply to: <django-users@googlegroups.com>
Date: Monday, 20 January 2020 at 22:07
To: Django users <django-users@googlegroups.com>
Subject: Backward migration failing because of old dropped model
Hi everyone,
This is my first post in this group so do not hesitate to ask for some more
specific details if this is not enough. Django version is 2.2.9, Python 3.6.
I'm facing an error when trying to migrate back the initial migration of a
freshly installed new application 'billing'.
The error message is the following one :
ValueError: The field form.Form.ticket_description was declared with a lazy
reference to 'tickets.ticketdescription', but app 'tickets' doesn't provide
model 'ticketdescription'.
However the model 'ticketdescription' has been dropped several month ago and is
no longer present in my project. Thus the part " app 'tickets' doesn't provide
model 'ticketdescription' " is perfectly right, but I don't get why it is not
managed by the migration of app 'tickets' which dropped the model
'ticketdescription'.
The model 'ticketdescription' remains as a pending model of state apps in the
migration executor, I would expect it to be removed.
Until now, I could migrate backward other apps without any issue but after
adding the app 'billing', which is not directly related to app 'tickets', it is
not possible anymore.
I don't know where to look at to fix this issue ? Could you help me debugging
please ? This looks like a bug but I'm not sure !
Best regards,
Adrien
Here is the full error trace :
Traceback (most recent call last):
File "manage.py", line 23, in <module>
execute_from_command_line(sys.argv)
File "[...]/lib/python3.6/site-packages/django/core/management/__init__.py",
line 381, in execute_from_command_line
utility.execute()
File "[...]/lib/python3.6/site-packages/django/core/management/__init__.py",
line 375, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "[...]/lib/python3.6/site-packages/django/core/management/base.py", line
323, in run_from_argv
self.execute(*args, **cmd_options)
File "[...]/lib/python3.6/site-packages/django/core/management/base.py", line
364, in execute
output = self.handle(*args, **options)
File "[...]/lib/python3.6/site-packages/django/core/management/base.py", line
83, in wrapped
res = handle_func(*args, **kwargs)
File
"[...]/lib/python3.6/site-packages/django/core/management/commands/migrate.py",
line 234, in handle
fake_initial=fake_initial,
File "[...]/lib/python3.6/site-packages/django/db/migrations/executor.py",
line 121, in migrate
state = self._migrate_all_backwards(plan, full_plan, fake=fake)
File "[...]/lib/python3.6/site-packages/django/db/migrations/executor.py",
line 173, in _migrate_all_backwards
for migration, _ in full_plan:
File "[...]/lib/python3.6/site-packages/django/utils/functional.py", line 80,
in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "[...]/lib/python3.6/site-packages/django/db/migrations/state.py", line
210, in apps
return StateApps(self.real_apps, self.models)
File "[...]/lib/python3.6/site-packages/django/db/migrations/state.py", line
280, in __init__
raise ValueError("\n".join(error.msg for error in errors))
ValueError: The field form.Form.ticket_description was declared with a lazy
reference to 'tickets.ticketdescription', but app 'tickets' doesn't provide
model 'ticketdescription'.
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