Unsupported object typing when using attr.ib with default

[danie1k]

This issue seems to be similar/continuation to #628.
pylint misunderstood typing when using attr.ib(default=...).

I've tried typing.cast & attr.ib with type attr and the result is the same.

Tested on

• Python 3.6.8
• pylint 2.3.1
• astroid 2.2.5

Steps to reproduce

1. Sample python file:

   # tst.py
   from typing import Set
   import attr
   
   class ApiKlass:
       def a_method(self):
           pass
   
   @attr.s
   class D1:
       d = attr.ib()
       api: ApiKlass = attr.ib(default=ApiKlass())
       values: Set = attr.ib(default=set)
   
       def test(self):
           return self.api.a_method
   
       def set_test(self, value: str):
           if value not in self.values:
               raise ValueError()

2. Run pylint tst.py.

Current behavior

[skip]
tst.py:16:15: E1101: Instance of '_CountingAttr' has no 'a_method' member (no-member)
[skip]
tst.py:19:24: E1135: Value 'self.values' doesn't support membership test (unsupported-membership-test)
tst.py:13:15: E1101: Instance of '_CountingAttr' has no 'a_method' member (no-member)

Expected behavior

Line 13 (class D1) should not raise no-member & unsupported-membership-test warnings.

python -c "from astroid import __pkginfo__; print(__pkginfo__.version)" output

[PCManticore]

@danie1k Thanks for reporting the issue. Right now pylint does not understand any typing support for attrs. For each library that does things somewhat in a dynamic way, in which bucket attrs falls as well, we have to write custom inference transforms . You are seeing these issues because no one got to add support for attrib defaults just yet.

[PCManticore]

Here's for example the current attrs transform: https://github.com/PyCQA/astroid/blob/master/astroid/brain/brain_attrs.py