Plugin appears to broken by astroid 2.9.1

[amdw]

With astroid 2.9.1, pylint-django appears not to work correctly.

For example, it produces errors like Class 'MyModel' has no 'objects' member (no-member), even when it should be able to infer that the objects member exists.

Full repro steps, including Pipenv.lock file with precise package versions, is available in the following repo:

https://github.com/amdw/pylint-django-repro

[jhofeditz]

I have the same problem. Downgrading to 2.11 fixes it.
• Updating astroid (2.9.1 -> 2.8.6)
• Updating pylint (2.12.2 -> 2.11.1)

[amdw]

With my repro, the problem can be fixed just by downgrading to astroid 2.9.0 (full instructions in the readme).

I'm unsure whether the actual problem here is in pylint-django, astroid or pylint.

It was quite difficult to debug this, as there were no error messages, just a silent failure to behave as expected. Fortunately I had a working project available, and I was able to start with the simple repro and downgrade dependencies one-by-one to match that project until I pinpointed that the problem was with astroid.

Also fortunately, astroid starts with an "a", so was one of the first dependencies I tried. :)

[amdw]

I should probably have also explicitly said that 2.9.1 is the latest version of astroid at the time of writing, released on 31st December.

So if people try to install pylint-django from a package manager like pip right now, they will run into this problem.

[grnxp]

The problem might be in astroid, in the scoped_nodes.py file or scoped_nodes module.

When pylint-django defines its register method, it tries from pylint_django.augmentations apply_augmentations.
At this point, we have an from astroid.scoped_nodes import ClassDef as ScopedClass, which crashes.

In Astroid version 2.9.1, the _is_metaclass function cannot be imported from astroid.nodes.scoped_nodes:

>>> from astroid.scoped_nodes import ClassDef
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/fred/.venvs/ultron/lib/python3.9/site-packages/astroid/scoped_nodes.py", line 5, in <module>
    from astroid.nodes.scoped_nodes import (
ImportError: cannot import name '_is_metaclass' from 'astroid.nodes.scoped_nodes' (/home/fred/.venvs/ultron/lib/python3.9/site-packages/astroid/nodes/scoped_nodes/__init__.py)

There might have been a change on this module between v2.9.0 and v2.9.1.

(I'll continue later this afternoon).

[carlio]

There is a deprecation warning that scoped_nodes is going away in astroid 3.0 - maybe that was brought forward.

[carlio]

@GrimBox can you try with the code on this branch https://github.com/PyCQA/pylint-django/tree/343-astroid-2.9.1-compat

That seems to fix things - at least the tests are passing. (except the code formatting one I will fix that ;-) )

[carlio]

I tested it with the repro repository, it works too so I will finish up some other bugs/PRs and get a release with the fix in.

Thanks for the awesome repro steps @amdw!

[grnxp]

@carlio Yes, it works for me too 👍 Thanks !

[carlio]

Cool!

So version 2.5.0 was just pushed to PyPI with this fix (and a couple of other improvements)