#25109: MigrationLoader.load_disk hides ImportError for invalid
MIGRATION_MODULES
----------------------------+--------------------
Reporter: blueyed | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+--------------------
With an invalid module name in `MIGRATION_MODULES`, you will get a rather
confusing `InvalidBasesError`:
{{{
InvalidBasesError: Cannot resolve bases for [<ModelState:
'djangocms_text_ckeditor.Text'>]
This can happen if you are inheriting models from an app with migrations
(e.g. contrib.auth)
in an app with no migrations; see
https://docs.djangoproject.com/en/1.8/topics/migrations/#dependencies for
more
}}}
This is caused by ignoring the `ImportError` in
https://github.com/django/django/blob/d72f8862cb1a39934952e708c3c869be1399846e/django/db/migrations/loader.py#L70-L78,
which is meant to handle non-existent migrations.
The following patch might fix it:
{{{
diff --git i/django/db/migrations/loader.py
w/django/db/migrations/loader.py
index a8f4be4..e872294 100644
--- i/django/db/migrations/loader.py
+++ w/django/db/migrations/loader.py
@@ -72,7 +72,9 @@ def load_disk(self):
except ImportError as e:
# I hate doing this, but I don't want to squash other
import errors.
# Might be better to try a directory check directly.
- if "No module named" in str(e) and MIGRATIONS_MODULE_NAME
in str(e):
+ if ("No module named" in str(e)
+ and MIGRATIONS_MODULE_NAME in str(e)
+ and app_config.label not in
settings.MIGRATION_MODULES):
self.unmigrated_apps.add(app_config.label)
continue
raise
}}}
But then Django's tests itself fail, because they use this "hack":
{{{
settings.MIGRATION_MODULES = {
# these 'tests.migrations' modules don't actually exist, but this
lets
# us skip creating migrations for the test models.
'auth': 'django.contrib.auth.tests.migrations',
'contenttypes': 'contenttypes_tests.migrations',
}
}}}
([Source](https://github.com/django/django/blob/d72f8862cb1a39934952e708c3c869be1399846e/tests/runtests.py#L142-147))
I've seen this issue multiple times in the context of Django CMS (and its
plugins), because in the progress of migrating to Django's migrations they
were using modules like `djangocms_text_ckeditor.migrations_django` which
then were renamed.
--
Ticket URL: <https://code.djangoproject.com/ticket/25109>
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