Autoreloader with StatReloader doesn't track changes in manage.py.

[Keryn Knight]

This is a bit convoluted, but here we go.

Environment (OSX 10.11):

$ python -V
Python 3.6.2
$ pip -V
pip 19.1.1
$ pip install Django==2.2.1

Steps to reproduce:

• Run a server python manage.py runserver
• Edit the manage.py file, e.g. add print():

  def main():
      print('sth')
      os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'ticket_30479.settings')
      ...
  

Under 2.1.8 (and prior), this will trigger the auto-reloading mechanism. Under 2.2.1, it won't. As far as I can tell from the django.utils.autoreload log lines, it never sees the manage.py itself.

[Mariusz Felisiak]

Thanks for the report. I simplified scenario.

Regression in c8720e7696ca41f3262d5369365cc1bd72a216ca.
Reproduced at 8d010f39869f107820421631111417298d1c5bb9.

[Tom Forbes]

Argh. I guess this is because manage.py isn't showing up in the sys.modules. I'm not sure I remember any specific manage.py handling in the old implementation, so I'm not sure how it used to work, but I should be able to fix this pretty easily.

[Keryn Knight]

Done a touch of debugging:

• iter_modules_and_files is where it gets lost.

Specifically, it ends up in there twice:

(<module '__future__' from '/../lib/python3.6/__future__.py'>,
 <module '__main__' from 'manage.py'>,
 <module '__main__' from 'manage.py'>,
 ...,)

But getattr(module, "__spec__", None) is None is True so it continues onwards. I thought I managed to get one of them to have a __spec__ attr but no has_location, but I can't seem to get that again (stepping around with pdb)

Digging into wtf __spec__ is None: ​Here's the py3 docs on it, which helpfully mentions that ​The one exception is __main__, where __spec__ is set to None in some cases

[Mariusz Felisiak]

Tom, will you have time to work on this in the next few days?

[Tom Forbes]

I'm sorry for assigning it to myself Mariusz, I intended to work on it on Tuesday but work overtook me and now I am travelling for a wedding this weekend. So I doubt it I'm afraid.

It seems Keryn's debugging is a great help, it should be somewhat simple to add special case handling for __main__, while __spec__ is None we can still get the filename and watch on that.

[Mariusz Felisiak]

np, Tom, thanks for info.

Keryn, it looks that you've already made most of the work. Would you like to prepare a patch?

[Tom Forbes]

Patch: ​https://github.com/django/django/pull/11422

[Mariusz Felisiak <felisiak.mariusz@…>]

In b2790f74:

Fixed #30479 -- Fixed detecting changes in manage.py by autoreloader when using StatReloader.

Regression in c8720e7696ca41f3262d5369365cc1bd72a216ca.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 5bf2c87e:

[2.2.x] Fixed #30479 -- Fixed detecting changes in manage.py by autoreloader when using StatReloader.

Regression in c8720e7696ca41f3262d5369365cc1bd72a216ca.

Backport of b2790f74d4f38c8b297b7c1cef6875d2378f6fa6 from master