As stated in https://code.djangoproject.com/ticket/26099, it is possible
for a project with an unfortunately named application to result in a
migration file being generated which will raise an error on attempting to
migrate, without any prior warning. The problem is that the following
imports can all be generated:
from django.db import migrations, models
from django.conf import settings
from django.utils.timezone import utc
If an application module is named models, migrations, settings or utc and
there is, for example, a function in one of those modules used for a
default of a field, its module will be imported as is and shadow the Django
import.
While the above names arguably aren't good choices for a module name, they
are valid, don't conflict with anything else within Django and the behavior
isn't mentioned in the documentation.
Here are several proposed solutions to the problem:
1. Mention the module names causing the bug to manifest in the
documentation, keep the behavior. This isn't likely to help the affected
users, and the name list must be kept in sync if new imports are added to
the generated migrations.
2. Warn about the name clash, refuse to generate the migration and tell the
user that they must rename a module. This might not be possible in case the
offending name is from a third party library.
3. Generate the imports without aliasing them (e.g. import django.db.models)
to make clashes impossible. This, however, makes the migration files harder
to read to a human, as all the imported names, like Model and Migration,
use full module names: django.db.models.Model,
django.db.migrations.Migration.
4. Only generate the un-aliased imports if there is a module name clash.
I have naively gone with option 3 and provided a patch (
https://github.com/django/django/pull/7810), but Tim Graham pointed out
that the deficiencies I was pondering too.
What is the best way forward here? I have an understanding of what's needed
to implement 4 and 2 (won't be much easier than 4) and can change the patch
accordingly.
Alexey
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