undefined-variable on correct return type hints

[craynic]

Steps to reproduce

code:

from enum import Enum


class Right:
    class Result1(Enum):
        OK = 0
    def work(self) -> Result1:
        return self.Result1.OK


class Wrong:
    class Result2(Enum):
        OK = 0
    def work(self) -> self.Result2:
        return self.Result2.OK

Got an error in running:

Traceback (most recent call last):
  File "tmp.py", line 11, in <module>
    class Wrong:
  File "tmp.py", line 14, in Wrong
    def work(self) -> self.Result2:
NameError: name 'self' is not defined

Current behavior

tmp.py:7:22: E0602: Undefined variable 'Result1' (undefined-variable)

Expected behavior

tmp.py:14:22: E0602: Undefined variable 'self' (undefined-variable)

pylint --version output

pylint 2.4.4
astroid 2.3.3
Python 3.8.2 (default, Feb 26 2020, 22:21:03)

The "right" code isn't really correct. You'd need to forward the reference: def work(self) -> "Result1":.

[craynic]

The "right" code isn't really correct. You'd need to forward the reference: def work(self) -> "Result1":.

I could run it with python with no problem. So that's correct.

If that's really not good enough, the message level should be W, not E.

[craynic]

any update?

I could run it with python with no problem. So that's correct.

You're right, my bad, mixed something up. It appears that pylint cannot handle type hints very well. def work(self) -> "Result1": seems to satisfy pylint but so does def work(self) -> "FooBar": which it shouldn't, of course.

[PCManticore]

Thanks for the report. This is definitely a bug, and it's unrelated to type hints. It's caused by pylint not properly scoping annotations in the enclosing scope.

For instance, if the code would be written like this, the error would not be emitted:

from enum import Enum

class Result1(Enum):
   OK = 0

class Right:
    def work(self) -> Result1:
        return Result1.OK

[craynic]

It seems to have been fixed in 2.5. Is it right?
If yes, hope a link to the PR or commit could be given.

[svenpanne]

No, this has not been fixed yet. I've just tried to convert some parts of our code base with https://github.com/ilevkivskyi/com2ann and stumbled over quite a few places which had to be fixed by hand (adding quotes) because pylint doesn't get the scoping right.

It is quite common that signatures of methods in a class Foo involve, well, Foo, so this pylint bug is really annoying in a large code base...

[svenpanne]

One more point: pylint should somehow treat typing.TYPE_CHECKING like mypy does, otherwise the scoping is screwed up for another reason.

[anjsimmo]

It seems to have been fixed in 2.5. Is it right?
If yes, hope a link to the PR or commit could be given.

@craynic Yes, the false positive for Result1 that you reported was fixed by PR #3497 and released in 2.5.0. I've submitted PR #3713 which should also fix the false negative for self.Result2 once merged.

(If converting a large code base, Pylint may encounter other type hint and scoping related issues--some of which have bug reports--but I think the specific case in this issue is now addressed)

[Pierre-Sassoulas]

Fixed in #3713