Regression: Value 'Collection' is unsubscriptable

[Spacerat]

Steps to reproduce

Run pylint on this file

from typing import Collection

def myfunc(arg: Collection[int]):
    print(arg)

myfunc([1, 2, 3])

Current behavior

repro.py:3:16: E1136: Value 'Collection' is unsubscriptable (unsubscriptable-object)

Expected behavior

No errors.

pylint --version output

Breaks for 2.1.0:

pylint 2.1.0
astroid 2.0.2
Python 3.6.4 (default, Mar 12 2018, 17:50:21)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.39.2)]

Does not break for 1.9.2:

pylint 1.9.2,
astroid 1.6.5
Python 3.6.4 (default, Mar 12 2018, 17:50:21)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.39.2)]

If there is a configuration workaround for this (except for disabling unsubscriptable-object globally) that would be nice, but neither ignored-modules=typing or ignored-classes=Collection worked for me.

[Spacerat]

In fact, this seems to be a Python 3.6 specific issue.

pylint 2.1.0
astroid 2.0.2
Python 3.7.0 (default, Aug  1 2018, 18:01:40)
[Clang 9.0.0 (clang-900.0.39.2)]

There's no issue for 3.7, so I'm not sure if this should be considered a regression

[PCManticore]

Hi, thanks for the report. I can also reproduce this bug.

[mthuurne]

This issue also happens for me with the following versions:

pylint 2.2.2
astroid 2.0.4
Python 3.6.5 (default, Mar 31 2018, 19:45:04) [GCC]

[mplanchard]

Also seeing this with

pylint 2.3.1
astroid 2.2.5
Python 3.6.8 (default, Mar  5 2019, 06:26:06)

[mthuurne]

Looking at the code of typing.py, the way Collection is defined is very different between Python 3.6 and 3.7, so fixing this might not be trivial.

I think ignored-classes=Collection does not help as a workaround because PyLint doesn't consider Collection a class on Python 3.6: it reports Value 'Collection' is unsubscriptable after all.

I ended up using this workaround:

from typing import TYPE_CHECKING, Collection

if not TYPE_CHECKING:
    # Work around PyLint issue on Python 3.6.
    #   https://github.com/PyCQA/pylint/issues/2377
    from typing import Sequence # pylint: disable=ungrouped-imports
    Collection = Sequence # pylint: disable=invalid-name

[tuukkamustonen]

Also occurs on python 3.5:

pylint 2.4.4
astroid 2.3.1
Python 3.5.5 (default, May 29 2018, 10:15:24) 
[GCC 5.4.0 20160609]

[jnsnow]

I'm working on adding pylint (+mypy) to all of QEMU's CI for our test infrastructure. We use Python 3.6 as our minimum viable python version for test infrastructure, so we are encountering this issue.

It appears to be an issue on all 2.x.x pylint versions against Python 3.6.10.

For now, my workaround will likely be just using Sequence instead of Collection.

[remort]

Still hurts on

pylint 2.6.0
astroid 2.4.2
Python 3.6.8 (default, Jan 30 2019, 23:58:16)