startapp template mustn't encourage using default_app_config

[Aymeric Augustin]

I just noticed that startapp now generates an apps.py. This isn't unreasonable. However it also sets default_app_config in __init__.py. I have strong doubts about this.

default_app_config is an ugly API that I included reluctantly for one targeted use-case: allowing pre-existing pluggable apps to take advantage of app config functionality in a backwards-compatible fashion, that is, without requiring projets to upgrade their INSTALLED_APPS settings. The first use of this feature was in django.contrib.admin in order to get rid of admin.autodiscover() in urls.py.

Relying implicitly on a default app config if one exists is clearly a bad practice. The good practice is to specifiy explicitly the full path to the AppConfig class in INSTALLED_APPS.

I recommend to:

• remove this line from app_template/__init__.py
• promote explicit configuration of app configs in INSTALLED_APPS
• clarify the docs of default_app_config with the information I described above

[Tim Graham]

​PR

[Tim Graham <timograham@…>]

In 862de0b:

Fixed #25356 -- Removed default_app_config from startapp template.

Also discouraged its use outside the intended use case.

[Aymeric Augustin]

Thanks Tim. Assigning to myself as a reminder to restructure the text a bit.

[Aymeric Augustin]

PR: ​https://github.com/django/django/pull/5331

[Aymeric Augustin <aymeric.augustin@…>]

In 94a36cfd:

Recommended against default_app_config.

Most likely this is a losing fight -- people seem to love this small
convention -- but at least the reasons for avoiding it will be
documented.

Refs #25356.

[Aymeric Augustin <aymeric.augustin@…>]

In 76bf4bc:

[1.8.x] Recommended against default_app_config.

Most likely this is a losing fight -- people seem to love this small
convention -- but at least the reasons for avoiding it will be
documented.

Refs #25356.

Backport of 94a36cf from master

[Tim Graham <timograham@…>]

In 6258e163:

Refs #24971, #25356 -- Clarified how apps.py works in 1.9 release notes.

[Tim Graham <timograham@…>]

In 7bbfc43e:

[1.9.x] Refs #24971, #25356 -- Clarified how apps.py works in 1.9 release notes.

Backport of 6258e163352690faf20bfc92c12468316d1a47ae from master