Forbid apps with conflicting labels or names

[Aymeric Augustin]

I'm almost sure Django misbehaves in a variety of ways when two apps have the same label. For starters, manage.py migrate will not pick models from one app.

Django should raise an exception if two apps have the same label. This must be implemented in Apps.populate_apps. It will make the current unicity check in django.conf redundant.

[loic84]

FWIW #12288 (from comment 32 onwards) has discussions regarding the backward compatibility implications of this change.

When I augment an external app {{ app_name }} with extra templates, templatetags or basically anything other than models, I have the convention of creating an app "{{ project_name }}.{{ app_name }}".

I'm not saying this change shouldn't happen, but that would be, by far, the biggest refactor required in my projects caused by a single change in Django core.

Maybe the actual app_label could be customized in AppConfig? That way, we wouldn't impose anything on how the python code should be laid out?

[loic84]

It seems #21683 proposes to do exactly that which answers all my concerns.

[Aymeric Augustin]

Yes #21683 is most likely a prerequisite to pull this off without getting stoned by our users.

[Aymeric Augustin]

AppConfig.name should also be unique across a project.

Currently there's a unicity check in django.conf but it's useless as it won't catch such duplicates.

[Aymeric Augustin]

PR: ​https://github.com/django/django/pull/2133

[Aymeric Augustin <aymeric.augustin@…>]

In 553500133cc4426f20407391f3493716357db45f:

Removed an obsolete unicity check.

It doesn't account for app configs.

Refs #21679.

[Aymeric Augustin <aymeric.augustin@…>]

In 5dfec4e23b4a3b81f8ec19bf0cf45147ad6b18e5:

Checked unicity of app config names when populating the app registry.

This check will miss duplicates until the check for duplicate labels is
added.

Refs #21679.

[Aymeric Augustin <aymeric.augustin@…>]

In 63137a8304d4387132e749c97aad1049526f601c:

Enforced unicity of app labels.

Fixed #21679.