ABC abstract properties raise W0633 when unpacked

[pylint-bot]

Originally reported by: Anonymous

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Here's the setup I used to check this:

#!python

"""
Test linting rule W0633.
"""

import abc


class TestClass(object):
    __metaclass__ = abc.ABCMeta

    def unpack(self):
        try:
            i, j = self.a # raises W0633
            x, y = self.b # doesn't raise W0633
        except ValueError:
            return

        print i, j, x, y

    @abc.abstractproperty
    def a(self):
        raise NotImplementedError

    @property
    def b(self):
        raise NotImplementedError

Currently the abstract property triggers W0633 but the built-in property does not. This behaviour seems strange given that abc.abstractproperty is a subclass of the builtin property. Neither should be raising this warning.

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• Bitbucket: https://bitbucket.org/logilab/pylint/issue/496

[pylint-bot]

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore):

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Using the latest astroid tip, you won't see the warning for the abstractproperty anymore. But what really happens here is that pylint will raise InferenceError when a function doesn't return anything, as it is the case for these two properties. So there's one question left. Should pylint emit W0633 for these cases, as they aren't returning a sequence at all or should we consider them abstract and ignore them?

[pylint-bot]

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore):

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I'll close the issue, the bug was fixed. Currently there many more checks which needs to handle the case where a function only raises an error and returns nothing, so we'll handle that later on.