id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
36544	"In some import sequence ./manage.py raises ""populate() isn't reentrant"" hiding the original error"	living-dev		"Hi,

I often add other command line entry points to my project, as a consequence, I ensure that whenever some code use my project code, all the django part is initialized if not already done. This can lead to a import sequence by manage.py that hides the real error.

Here is a reproduction scenario:

{{{
$ python -m venv bug
$ cd bug/
$ . ./bin/activate
$ pip install django==5.2.5
$ django-admin startproject bug
$ cd bug
$ ./manage.py startapp an_app
$ ./manage.py startapp bad_import
}}}

Add ""an_app"" and ""bad_import""  to INSTALLED_APPS:

{{{
INSTALLED_APPS = [
...
    'an_app',
    'bad_import',
]
}}}

Here the automatic django initialization code:

{{{
$ cat > bug/__init__.py << EOF
import os

import django

from django.conf import settings
from django.apps import apps
if not settings.configured and not apps.loading:
    os.environ['DJANGO_SETTINGS_MODULE'] = 'bug.settings'
    django.setup()
EOF
}}}

And a custom entry point under bug project:

{{{
$ cat > bug/cli.py << EOF
from django.conf import settings
if __name__ == '__main__':
    print('My CLI entry point:', settings.configured)
EOF
}}}

At this point both cli and `manage.py` are working:

{{{

$ python -m bug.cli
My CLI entry point: True
$ ./manage.py 
Type 'manage.py help <subcommand>' for help on a specific subcommand.
...
}}}

Now we introduce a bad import line because of typo error in the models:

{{{
$ echo 'import an_app.model' >> bad_import/models.py
}}}

When using our cli entry point, the error is clear:

{{{
$ python -m bug.cli
Traceback (most recent call last):
...
  File ""/home/debian/Support/django/bug-20250807/bug/bug/bug/__init__.py"", line 9, in <module>
    django.setup()
...
  File ""/home/debian/Support/django/bug-20250807/bug/bug/bad_import/models.py"", line 3, in <module>
    import an_app.model
ModuleNotFoundError: No module named 'an_app.model'
}}}

But when we use manage.py, the error is hidden:

{{{
$ ./manage.py 
Traceback (most recent call last):
...
  File ""/home/debian/Support/django/bug-20250807/bug/lib/python3.11/site-packages/django/core/management/__init__.py"", line 416, in execute
    django.setup()
  File ""/home/debian/Support/django/bug-20250807/bug/lib/python3.11/site-packages/django/__init__.py"", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File ""/home/debian/Support/django/bug-20250807/bug/lib/python3.11/site-packages/django/apps/registry.py"", line 83, in populate
    raise RuntimeError(""populate() isn't reentrant"")
RuntimeError: populate() isn't reentrant
}}}

In fact the error is memorized in `django/core/management/__init__.py:381`:

{{{
        try:
            settings.INSTALLED_APPS
        except ImproperlyConfigured as exc:
            self.settings_exception = exc
        except ImportError as exc:
            self.settings_exception = exc
}}}

But we finish on this part, that triggers the reentrant populate `django/core/management/__init__.py:414`:

{{{
            # In all other cases, django.setup() is required to succeed.
            else:
                django.setup()
}}}

I think it could be simply resolved by propagating the memorized exception if `django.setup()` fails, so the trace is more explicit:

{{{
            # In all other cases, django.setup() is required to succeed.
            else:
                try:
                    django.setup()
                except Exception as exc:
                    raise exc from self.settings_exception
}}}

In this case the stack trace can help as it shows both the original error and that we also call `django.setup()` twice:

{{{
$ ./manage.py 
Traceback (most recent call last):
  File ""/home/debian/Support/django/bug-20250807/bug/lib/python3.11/site-packages/django/core/management/__init__.py"", line 382, in execute
    settings.INSTALLED_APPS
...
  File ""/home/debian/Support/django/bug-20250807/bug/bug/bug/__init__.py"", line 9, in <module>
    django.setup()
...
  File ""/home/debian/Support/django/bug-20250807/bug/bug/bad_import/models.py"", line 3, in <module>
    from an_app.model import Model
ModuleNotFoundError: No module named 'an_app.model'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File ""/home/debian/Support/django/bug-20250807/bug/bug/./manage.py"", line 22, in <module>
    main()
...
  File ""/home/debian/Support/django/bug-20250807/bug/lib/python3.11/site-packages/django/core/management/__init__.py"", line 417, in execute
    django.setup()
...
  File ""/home/debian/Support/django/bug-20250807/bug/lib/python3.11/site-packages/django/apps/registry.py"", line 83, in populate
    raise RuntimeError(""populate() isn't reentrant"")
RuntimeError: populate() isn't reentrant
}}}

Best Regards,
"	Bug	closed	Core (Management commands)	5.2	Normal	duplicate	populate reentrant manage.py ImportError		Unreviewed	0	0	0	0	0	0