Incorrect handling of property overriding in subclasses.

[dcbaker]

pylint: 1.5.4
astroid 1.4.4
python: 2.7.11, 3.3.6, 3.5.1

If a class wants to override the getter or setter of a property in the parent class, then pylint incorrectly marks it as a "no-member" error, the code runs and works as expected.

class Parent(object):
    def __init__(self):
        self.__thing = 'foo'

    @property
    def thing(self):
        return self.__thing


class Child(Parent):
    @Parent.thing.getter
    def thing(self):
        return super(Child, self).thing + '!'


print(Child().thing)

I believe that the corollary to this case is that the following case is invalid, but marked as valid by pylint:

class Parent(object):
    def __init__(self):
        self.__thing = 'foo'

    @property
    def thing(self):
        return self.__thing


class Child(Parent):
    @thing.getter
    def thing(self):
        return super(Child, self).thing + '!'


print(Child().thing)

[PCManticore]

True, but this seems like an edge right now. We might improve it though with Pylint / astroid 2.0.

[leynos]

This seems to suddenly have started affecting my Tornado RequestHandler subclass since installing pylint-1.5.5. I get a slew of no-member errors from field accesses to objects returned by self.current_user (which is a property). Downgrading to pylint-1.5.4 and astroid-1.4.4 fixes this.

Since the OP reports this as affecting pylint-1.5.4 and astroid-1.4.4, I wonder if I am experiencing a separate unrelated issue, or if the two are connected.

[PCManticore]

Can you show me an example of how the RequestHandler subclass looks with respect to the current_user property? I'm trying to see if it is the same issue as this one.

[leynos]

An example of this:

from tornado.web import RequestHandler

class User(object):

    def __init__(self):
        self.foo = 'foo'
        self.bar = 'bar'
        self.qux = 'qux'

class MyRequestHandlerSubclass(RequestHandler):

    def get_current_user(self):
        return User()

class TestRequestHandler(MyRequestHandlerSubclass):

    def get(self):

        print(self.current_user.foo)

The method get_current_user() is called by the current_user property and cached. (See: http://www.tornadoweb.org/en/stable/_modules/tornado/web.html#RequestHandler.get_current_user).

The following is displayed by pylint:

E: 19,14: Method 'current_user' has no 'foo' member (no-member)

[sscherfke]

With Tornado 6, calling methods like tornado.web.RequestHandler.get_argument('name') leads to E1120: No value for argument 'default' in method call (no-value-for-parameter) errors b/c of their overload decorators

[backbord]

I think this related to #1623 and thusly to #1581

[sscherfke]

A workaround for Tornado 6 is the following astroid brain:

# astroid/brain/brain_tornado.py
"""
Astroid hooks for tornado.

"""
import astroid


def requesthandler_funcs():
    return astroid.parse(
        """
        from tornado.web import RequestHandler

        class RequestHandlerMock(RequestHandler):
            def get_argument(name, default=None, strip=True):
                return object()
        """
    )


astroid.register_module_extender(astroid.MANAGER, 'tornado.web', requesthandler_funcs)