inconsistent-mro , but Python does not raise error

[pierluca]

Steps to reproduce

1. pip install autobahn[twisted]
2. Try linting the following code:

from twisted.internet.protocol import ReconnectingClientFactory
from autobahn.twisted import websocket


class RetryFactory(websocket.WampWebSocketClientFactory,
                   ReconnectingClientFactory):
    pass

Current behavior

poc.py:5: [R0901(too-many-ancestors), RetryFactory] Too many ancestors (11/7)
poc.py:5: [E0240(inconsistent-mro), RetryFactory] Inconsistent method resolution order for class 'RetryFactory'

Expected behavior

poc.py:5: [R0901(too-many-ancestors), RetryFactory] Too many ancestors (11/7)

Too many ancestors is expected, given the library imports at hand.
However, we can't reproduce the inconsistent method resolution order on a Python execution of the script. Isn't this a false positive?

pylint --version output

pylint 1.6.5, 
astroid 1.4.9
Python 2.7.9 (default, Jun 29 2016, 13:08:31) 
[GCC 4.9.2]

[PCManticore]

It might be a false positive. We are trying to compute the MRO, but we might have some edge cases we didn't handle properly when we first implemented the algorithm. Thank you, will take a look.

[rogalski]

There is a magic decorator in twisted source that converts old-style class to new-style classes in runtime. Most likely Pylint still sees this class as old-style class, which changes the way MRO works. Our C3 algorithm implementation looks fine to be honest.

[rogalski]

class Factory(object):  # make it old-style class to trigger an error
    pass


class ClientFactory(Factory):
    pass


class ReconnectingClientFactory(ClientFactory):
    pass


class WebSocketAdapterFactory(object):
    pass


class WebSocketClientFactory(WebSocketAdapterFactory, ClientFactory):
    pass


class WampWebSocketClientFactory(WebSocketClientFactory):
    pass


class RetryFactory(WampWebSocketClientFactory, ReconnectingClientFactory):
    pass

Slightly smaller, standalone reproduction.

[PCManticore]

Closed in astroid's master by pylint-dev/astroid@5092504