Move all package files to a pylint package.

1 files changed, 982 insertions, 0 deletions

diff --git a/pylint/checkers/classes.py b/pylint/checkers/classes.py
new file mode 100644
index 0000000..8e51a47
--- /dev/null
+++ b/pylint/checkers/classes.py
@@ -0,0 +1,982 @@
+# Copyright (c) 2003-2014 LOGILAB S.A. (Paris, FRANCE).
+# http://www.logilab.fr/ -- mailto:contact@logilab.fr
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+"""classes checker for Python code
+"""
+from __future__ import generators
+
+import sys
+from collections import defaultdict
+
+import astroid
+from astroid import YES, Instance, are_exclusive, AssAttr, Class
+from astroid.bases import Generator, BUILTINS
+from astroid.inference import InferenceContext
+
+from pylint.interfaces import IAstroidChecker
+from pylint.checkers import BaseChecker
+from pylint.checkers.utils import (
+    PYMETHODS, overrides_a_method, check_messages, is_attr_private,
+    is_attr_protected, node_frame_class, safe_infer, is_builtin_object,
+    decorated_with_property, unimplemented_abstract_methods)
+import six
+
+if sys.version_info >= (3, 0):
+    NEXT_METHOD = '__next__'
+else:
+    NEXT_METHOD = 'next'
+ITER_METHODS = ('__iter__', '__getitem__')
+
+def _called_in_methods(func, klass, methods):
+    """ Check if the func was called in any of the given methods,
+    belonging to the *klass*. Returns True if so, False otherwise.
+    """
+    if not isinstance(func, astroid.Function):
+        return False
+    for method in methods:
+        try:
+            infered = klass.getattr(method)
+        except astroid.NotFoundError:
+            continue
+        for infer_method in infered:
+            for callfunc in infer_method.nodes_of_class(astroid.CallFunc):
+                try:
+                    bound = next(callfunc.func.infer())
+                except (astroid.InferenceError, StopIteration):
+                    continue
+                if not isinstance(bound, astroid.BoundMethod):
+                    continue
+                func_obj = bound._proxied
+                if isinstance(func_obj, astroid.UnboundMethod):
+                    func_obj = func_obj._proxied
+                if func_obj.name == func.name:
+                    return True
+    return False
+
+def class_is_abstract(node):
+    """return true if the given class node should be considered as an abstract
+    class
+    """
+    for method in node.methods():
+        if method.parent.frame() is node:
+            if method.is_abstract(pass_is_abstract=False):
+                return True
+    return False
+
+def _is_attribute_property(name, klass):
+    """ Check if the given attribute *name* is a property
+    in the given *klass*.
+
+    It will look for `property` calls or for functions
+    with the given name, decorated by `property` or `property`
+    subclasses.
+    Returns ``True`` if the name is a property in the given klass,
+    ``False`` otherwise.
+    """
+
+    try:
+        attributes = klass.getattr(name)
+    except astroid.NotFoundError:
+        return False
+    property_name = "{0}.property".format(BUILTINS)
+    for attr in attributes:
+        try:
+            infered = next(attr.infer())
+        except astroid.InferenceError:
+            continue
+        if (isinstance(infered, astroid.Function) and
+                decorated_with_property(infered)):
+            return True
+        if infered.pytype() == property_name:
+            return True
+    return False
+
+
+MSGS = {
+    'F0202': ('Unable to check methods signature (%s / %s)',
+              'method-check-failed',
+              'Used when Pylint has been unable to check methods signature \
+              compatibility for an unexpected reason. Please report this kind \
+              if you don\'t make sense of it.'),
+
+    'E0202': ('An attribute defined in %s line %s hides this method',
+              'method-hidden',
+              'Used when a class defines a method which is hidden by an '
+              'instance attribute from an ancestor class or set by some '
+              'client code.'),
+    'E0203': ('Access to member %r before its definition line %s',
+              'access-member-before-definition',
+              'Used when an instance member is accessed before it\'s actually\
+              assigned.'),
+    'W0201': ('Attribute %r defined outside __init__',
+              'attribute-defined-outside-init',
+              'Used when an instance attribute is defined outside the __init__\
+              method.'),
+
+    'W0212': ('Access to a protected member %s of a client class', # E0214
+              'protected-access',
+              'Used when a protected member (i.e. class member with a name \
+              beginning with an underscore) is access outside the class or a \
+              descendant of the class where it\'s defined.'),
+
+    'E0211': ('Method has no argument',
+              'no-method-argument',
+              'Used when a method which should have the bound instance as \
+              first argument has no argument defined.'),
+    'E0213': ('Method should have "self" as first argument',
+              'no-self-argument',
+              'Used when a method has an attribute different the "self" as\
+              first argument. This is considered as an error since this is\
+              a so common convention that you shouldn\'t break it!'),
+    'C0202': ('Class method %s should have %s as first argument', # E0212
+              'bad-classmethod-argument',
+              'Used when a class method has a first argument named differently '
+              'than the value specified in valid-classmethod-first-arg option '
+              '(default to "cls"), recommended to easily differentiate them '
+              'from regular instance methods.'),
+    'C0203': ('Metaclass method %s should have %s as first argument', # E0214
+              'bad-mcs-method-argument',
+              'Used when a metaclass method has a first agument named '
+              'differently than the value specified in valid-classmethod-first'
+              '-arg option (default to "cls"), recommended to easily '
+              'differentiate them from regular instance methods.'),
+    'C0204': ('Metaclass class method %s should have %s as first argument',
+              'bad-mcs-classmethod-argument',
+              'Used when a metaclass class method has a first argument named '
+              'differently than the value specified in valid-metaclass-'
+              'classmethod-first-arg option (default to "mcs"), recommended to '
+              'easily differentiate them from regular instance methods.'),
+
+    'W0211': ('Static method with %r as first argument',
+              'bad-staticmethod-argument',
+              'Used when a static method has "self" or a value specified in '
+              'valid-classmethod-first-arg option or '
+              'valid-metaclass-classmethod-first-arg option as first argument.'
+             ),
+    'R0201': ('Method could be a function',
+              'no-self-use',
+              'Used when a method doesn\'t use its bound instance, and so could\
+              be written as a function.'
+             ),
+
+    'E0221': ('Interface resolved to %s is not a class',
+              'interface-is-not-class',
+              'Used when a class claims to implement an interface which is not \
+              a class.'),
+    'E0222': ('Missing method %r from %s interface',
+              'missing-interface-method',
+              'Used when a method declared in an interface is missing from a \
+              class implementing this interface'),
+    'W0221': ('Arguments number differs from %s %r method',
+              'arguments-differ',
+              'Used when a method has a different number of arguments than in \
+              the implemented interface or in an overridden method.'),
+    'W0222': ('Signature differs from %s %r method',
+              'signature-differs',
+              'Used when a method signature is different than in the \
+              implemented interface or in an overridden method.'),
+    'W0223': ('Method %r is abstract in class %r but is not overridden',
+              'abstract-method',
+              'Used when an abstract method (i.e. raise NotImplementedError) is \
+              not overridden in concrete class.'
+             ),
+    'F0220': ('failed to resolve interfaces implemented by %s (%s)', # W0224
+              'unresolved-interface',
+              'Used when a Pylint as failed to find interfaces implemented by \
+               a class'),
+
+
+    'W0231': ('__init__ method from base class %r is not called',
+              'super-init-not-called',
+              'Used when an ancestor class method has an __init__ method \
+              which is not called by a derived class.'),
+    'W0232': ('Class has no __init__ method',
+              'no-init',
+              'Used when a class has no __init__ method, neither its parent \
+              classes.'),
+    'W0233': ('__init__ method from a non direct base class %r is called',
+              'non-parent-init-called',
+              'Used when an __init__ method is called on a class which is not \
+              in the direct ancestors for the analysed class.'),
+    'W0234': ('__iter__ returns non-iterator',
+              'non-iterator-returned',
+              'Used when an __iter__ method returns something which is not an \
+               iterable (i.e. has no `%s` method)' % NEXT_METHOD),
+    'E0235': ('__exit__ must accept 3 arguments: type, value, traceback',
+              'bad-context-manager',
+              'Used when the __exit__ special method, belonging to a \
+               context manager, does not accept 3 arguments \
+               (type, value, traceback).'),
+    'E0236': ('Invalid object %r in __slots__, must contain '
+              'only non empty strings',
+              'invalid-slots-object',
+              'Used when an invalid (non-string) object occurs in __slots__.'),
+    'E0237': ('Assigning to attribute %r not defined in class slots',
+              'assigning-non-slot',
+              'Used when assigning to an attribute not defined '
+              'in the class slots.'),
+    'E0238': ('Invalid __slots__ object',
+              'invalid-slots',
+              'Used when an invalid __slots__ is found in class. '
+              'Only a string, an iterable or a sequence is permitted.'),
+    'E0239': ('Inheriting %r, which is not a class.',
+              'inherit-non-class',
+              'Used when a class inherits from something which is not a '
+              'class.'),
+
+
+    }
+
+
+class ClassChecker(BaseChecker):
+    """checks for :
+    * methods without self as first argument
+    * overridden methods signature
+    * access only to existent members via self
+    * attributes not defined in the __init__ method
+    * supported interfaces implementation
+    * unreachable code
+    """
+
+    __implements__ = (IAstroidChecker,)
+
+    # configuration section name
+    name = 'classes'
+    # messages
+    msgs = MSGS
+    priority = -2
+    # configuration options
+    options = (('ignore-iface-methods',
+                {'default' : (#zope interface
+                    'isImplementedBy', 'deferred', 'extends', 'names',
+                    'namesAndDescriptions', 'queryDescriptionFor', 'getBases',
+                    'getDescriptionFor', 'getDoc', 'getName', 'getTaggedValue',
+                    'getTaggedValueTags', 'isEqualOrExtendedBy', 'setTaggedValue',
+                    'isImplementedByInstancesOf',
+                    # twisted
+                    'adaptWith',
+                    # logilab.common interface
+                    'is_implemented_by'),
+                 'type' : 'csv',
+                 'metavar' : '<method names>',
+                 'help' : 'List of interface methods to ignore, \
+separated by a comma. This is used for instance to not check methods defines \
+in Zope\'s Interface base class.'}
+               ),
+               ('defining-attr-methods',
+                {'default' : ('__init__', '__new__', 'setUp'),
+                 'type' : 'csv',
+                 'metavar' : '<method names>',
+                 'help' : 'List of method names used to declare (i.e. assign) \
+instance attributes.'}
+               ),
+               ('valid-classmethod-first-arg',
+                {'default' : ('cls',),
+                 'type' : 'csv',
+                 'metavar' : '<argument names>',
+                 'help' : 'List of valid names for the first argument in \
+a class method.'}
+               ),
+               ('valid-metaclass-classmethod-first-arg',
+                {'default' : ('mcs',),
+                 'type' : 'csv',
+                 'metavar' : '<argument names>',
+                 'help' : 'List of valid names for the first argument in \
+a metaclass class method.'}
+               ),
+               ('exclude-protected',
+                {
+                    'default': (
+                        # namedtuple public API.
+                        '_asdict', '_fields', '_replace', '_source', '_make'),
+                    'type': 'csv',
+                    'metavar': '<protected access exclusions>',
+                    'help': ('List of member names, which should be excluded '
+                             'from the protected access warning.')}
+               ))
+
+    def __init__(self, linter=None):
+        BaseChecker.__init__(self, linter)
+        self._accessed = []
+        self._first_attrs = []
+        self._meth_could_be_func = None
+
+    def visit_class(self, node):
+        """init visit variable _accessed and check interfaces
+        """
+        self._accessed.append(defaultdict(list))
+        self._check_bases_classes(node)
+        self._check_interfaces(node)
+        # if not an interface, exception, metaclass
+        if node.type == 'class':
+            try:
+                node.local_attr('__init__')
+            except astroid.NotFoundError:
+                self.add_message('no-init', args=node, node=node)
+        self._check_slots(node)
+        self._check_proper_bases(node)
+
+    @check_messages('inherit-non-class')
+    def _check_proper_bases(self, node):
+        """
+        Detect that a class inherits something which is not
+        a class or a type.
+        """
+        for base in node.bases:
+            ancestor = safe_infer(base)
+            if ancestor in (YES, None):
+                continue
+            if (isinstance(ancestor, astroid.Instance) and
+                    ancestor.is_subtype_of('%s.type' % (BUILTINS,))):
+                continue
+            if not isinstance(ancestor, astroid.Class):
+                self.add_message('inherit-non-class',
+                                 args=base.as_string(), node=node)
+
+    @check_messages('access-member-before-definition',
+                    'attribute-defined-outside-init')
+    def leave_class(self, cnode):
+        """close a class node:
+        check that instance attributes are defined in __init__ and check
+        access to existent members
+        """
+        # check access to existent members on non metaclass classes
+        accessed = self._accessed.pop()
+        if cnode.type != 'metaclass':
+            self._check_accessed_members(cnode, accessed)
+        # checks attributes are defined in an allowed method such as __init__
+        if not self.linter.is_message_enabled('attribute-defined-outside-init'):
+            return
+        defining_methods = self.config.defining_attr_methods
+        current_module = cnode.root()
+        for attr, nodes in six.iteritems(cnode.instance_attrs):
+            # skip nodes which are not in the current module and it may screw up
+            # the output, while it's not worth it
+            nodes = [n for n in nodes if not
+                     isinstance(n.statement(), (astroid.Delete, astroid.AugAssign))
+                     and n.root() is current_module]
+            if not nodes:
+                continue # error detected by typechecking
+            # check if any method attr is defined in is a defining method
+            if any(node.frame().name in defining_methods
+                   for node in nodes):
+                continue
+
+            # check attribute is defined in a parent's __init__
+            for parent in cnode.instance_attr_ancestors(attr):
+                attr_defined = False
+                # check if any parent method attr is defined in is a defining method
+                for node in parent.instance_attrs[attr]:
+                    if node.frame().name in defining_methods:
+                        attr_defined = True
+                if attr_defined:
+                    # we're done :)
+                    break
+            else:
+                # check attribute is defined as a class attribute
+                try:
+                    cnode.local_attr(attr)
+                except astroid.NotFoundError:
+                    for node in nodes:
+                        if node.frame().name not in defining_methods:
+                            # If the attribute was set by a callfunc in any
+                            # of the defining methods, then don't emit
+                            # the warning.
+                            if _called_in_methods(node.frame(), cnode,
+                                                  defining_methods):
+                                continue
+                            self.add_message('attribute-defined-outside-init',
+                                             args=attr, node=node)
+
+    def visit_function(self, node):
+        """check method arguments, overriding"""
+        # ignore actual functions
+        if not node.is_method():
+            return
+        klass = node.parent.frame()
+        self._meth_could_be_func = True
+        # check first argument is self if this is actually a method
+        self._check_first_arg_for_type(node, klass.type == 'metaclass')
+        if node.name == '__init__':
+            self._check_init(node)
+            return
+        # check signature if the method overloads inherited method
+        for overridden in klass.local_attr_ancestors(node.name):
+            # get astroid for the searched method
+            try:
+                meth_node = overridden[node.name]
+            except KeyError:
+                # we have found the method but it's not in the local
+                # dictionary.
+                # This may happen with astroid build from living objects
+                continue
+            if not isinstance(meth_node, astroid.Function):
+                continue
+            self._check_signature(node, meth_node, 'overridden')
+            break
+        if node.decorators:
+            for decorator in node.decorators.nodes:
+                if isinstance(decorator, astroid.Getattr) and \
+                        decorator.attrname in ('getter', 'setter', 'deleter'):
+                    # attribute affectation will call this method, not hiding it
+                    return
+                if isinstance(decorator, astroid.Name) and decorator.name == 'property':
+                    # attribute affectation will either call a setter or raise
+                    # an attribute error, anyway not hiding the function
+                    return
+        # check if the method is hidden by an attribute
+        try:
+            overridden = klass.instance_attr(node.name)[0] # XXX
+            overridden_frame = overridden.frame()
+            if (isinstance(overridden_frame, astroid.Function)
+                    and overridden_frame.type == 'method'):
+                overridden_frame = overridden_frame.parent.frame()
+            if (isinstance(overridden_frame, Class)
+                    and klass.is_subtype_of(overridden_frame.qname())):
+                args = (overridden.root().name, overridden.fromlineno)
+                self.add_message('method-hidden', args=args, node=node)
+        except astroid.NotFoundError:
+            pass
+
+        # check non-iterators in __iter__
+        if node.name == '__iter__':
+            self._check_iter(node)
+        elif node.name == '__exit__':
+            self._check_exit(node)
+
+    def _check_slots(self, node):
+        if '__slots__' not in node.locals:
+            return
+        for slots in node.igetattr('__slots__'):
+            # check if __slots__ is a valid type
+            for meth in ITER_METHODS:
+                try:
+                    slots.getattr(meth)
+                    break
+                except astroid.NotFoundError:
+                    continue
+            else:
+                self.add_message('invalid-slots', node=node)
+                continue
+
+            if isinstance(slots, astroid.Const):
+                # a string, ignore the following checks
+                continue
+            if not hasattr(slots, 'itered'):
+                # we can't obtain the values, maybe a .deque?
+                continue
+
+            if isinstance(slots, astroid.Dict):
+                values = [item[0] for item in slots.items]
+            else:
+                values = slots.itered()
+            if values is YES:
+                return
+
+            for elt in values:
+                try:
+                    self._check_slots_elt(elt)
+                except astroid.InferenceError:
+                    continue
+
+    def _check_slots_elt(self, elt):
+        for infered in elt.infer():
+            if infered is YES:
+                continue
+            if (not isinstance(infered, astroid.Const) or
+                    not isinstance(infered.value, six.string_types)):
+                self.add_message('invalid-slots-object',
+                                 args=infered.as_string(),
+                                 node=elt)
+                continue
+            if not infered.value:
+                self.add_message('invalid-slots-object',
+                                 args=infered.as_string(),
+                                 node=elt)
+
+    def _check_iter(self, node):
+        try:
+            infered = node.infer_call_result(node)
+        except astroid.InferenceError:
+            return
+
+        for infered_node in infered:
+            if (infered_node is YES
+                    or isinstance(infered_node, Generator)):
+                continue
+            if isinstance(infered_node, astroid.Instance):
+                try:
+                    infered_node.local_attr(NEXT_METHOD)
+                except astroid.NotFoundError:
+                    self.add_message('non-iterator-returned',
+                                     node=node)
+                    break
+
+    def _check_exit(self, node):
+        positional = sum(1 for arg in node.args.args if arg.name != 'self')
+        if positional < 3 and not node.args.vararg:
+            self.add_message('bad-context-manager',
+                             node=node)
+        elif positional > 3:
+            self.add_message('bad-context-manager',
+                             node=node)
+
+    def leave_function(self, node):
+        """on method node, check if this method couldn't be a function
+
+        ignore class, static and abstract methods, initializer,
+        methods overridden from a parent class and any
+        kind of method defined in an interface for this warning
+        """
+        if node.is_method():
+            if node.args.args is not None:
+                self._first_attrs.pop()
+            if not self.linter.is_message_enabled('no-self-use'):
+                return
+            class_node = node.parent.frame()
+            if (self._meth_could_be_func and node.type == 'method'
+                    and not node.name in PYMETHODS
+                    and not (node.is_abstract() or
+                             overrides_a_method(class_node, node.name))
+                    and class_node.type != 'interface'):
+                self.add_message('no-self-use', node=node)
+
+    def visit_getattr(self, node):
+        """check if the getattr is an access to a class member
+        if so, register it. Also check for access to protected
+        class member from outside its class (but ignore __special__
+        methods)
+        """
+        attrname = node.attrname
+        # Check self
+        if self.is_first_attr(node):
+            self._accessed[-1][attrname].append(node)
+            return
+        if not self.linter.is_message_enabled('protected-access'):
+            return
+
+        self._check_protected_attribute_access(node)
+
+    def visit_assattr(self, node):
+        if isinstance(node.ass_type(), astroid.AugAssign) and self.is_first_attr(node):
+            self._accessed[-1][node.attrname].append(node)
+        self._check_in_slots(node)
+
+    def _check_in_slots(self, node):
+        """ Check that the given assattr node
+        is defined in the class slots.
+        """
+        infered = safe_infer(node.expr)
+        if infered and isinstance(infered, Instance):
+            klass = infered._proxied
+            if '__slots__' not in klass.locals or not klass.newstyle:
+                return
+
+            slots = klass.slots()
+            if slots is None:
+                return
+            # If any ancestor doesn't use slots, the slots
+            # defined for this class are superfluous.
+            if any('__slots__' not in ancestor.locals and
+                   ancestor.name != 'object'
+                   for ancestor in klass.ancestors()):
+                return
+
+            if not any(slot.value == node.attrname for slot in slots):
+                # If we have a '__dict__' in slots, then
+                # assigning any name is valid.
+                if not any(slot.value == '__dict__' for slot in slots):
+                    if _is_attribute_property(node.attrname, klass):
+                        # Properties circumvent the slots mechanism,
+                        # so we should not emit a warning for them.
+                        return
+                    self.add_message('assigning-non-slot',
+                                     args=(node.attrname, ), node=node)
+
+    @check_messages('protected-access')
+    def visit_assign(self, assign_node):
+        node = assign_node.targets[0]
+        if not isinstance(node, AssAttr):
+            return
+
+        if self.is_first_attr(node):
+            return
+
+        self._check_protected_attribute_access(node)
+
+    def _check_protected_attribute_access(self, node):
+        '''Given an attribute access node (set or get), check if attribute
+        access is legitimate. Call _check_first_attr with node before calling
+        this method. Valid cases are:
+        * self._attr in a method or cls._attr in a classmethod. Checked by
+        _check_first_attr.
+        * Klass._attr inside "Klass" class.
+        * Klass2._attr inside "Klass" class when Klass2 is a base class of
+            Klass.
+        '''
+        attrname = node.attrname
+
+        if (is_attr_protected(attrname) and
+                attrname not in self.config.exclude_protected):
+
+            klass = node_frame_class(node)
+
+            # XXX infer to be more safe and less dirty ??
+            # in classes, check we are not getting a parent method
+            # through the class object or through super
+            callee = node.expr.as_string()
+
+            # We are not in a class, no remaining valid case
+            if klass is None:
+                self.add_message('protected-access', node=node, args=attrname)
+                return
+
+            # If the expression begins with a call to super, that's ok.
+            if isinstance(node.expr, astroid.CallFunc) and \
+               isinstance(node.expr.func, astroid.Name) and \
+               node.expr.func.name == 'super':
+                return
+
+            # We are in a class, one remaining valid cases, Klass._attr inside
+            # Klass
+            if not (callee == klass.name or callee in klass.basenames):
+                # Detect property assignments in the body of the class.
+                # This is acceptable:
+                #
+                # class A:
+                #     b = property(lambda: self._b)
+
+                stmt = node.parent.statement()
+                try:
+                    if (isinstance(stmt, astroid.Assign) and
+                            (stmt in klass.body or klass.parent_of(stmt)) and
+                            isinstance(stmt.value, astroid.CallFunc) and
+                            isinstance(stmt.value.func, astroid.Name) and
+                            stmt.value.func.name == 'property' and
+                            is_builtin_object(next(stmt.value.func.infer(), None))):
+                        return
+                except astroid.InferenceError:
+                    pass
+                self.add_message('protected-access', node=node, args=attrname)
+
+    def visit_name(self, node):
+        """check if the name handle an access to a class member
+        if so, register it
+        """
+        if self._first_attrs and (node.name == self._first_attrs[-1] or
+                                  not self._first_attrs[-1]):
+            self._meth_could_be_func = False
+
+    def _check_accessed_members(self, node, accessed):
+        """check that accessed members are defined"""
+        # XXX refactor, probably much simpler now that E0201 is in type checker
+        for attr, nodes in six.iteritems(accessed):
+            # deactivate "except doesn't do anything", that's expected
+            # pylint: disable=W0704
+            try:
+                # is it a class attribute ?
+                node.local_attr(attr)
+                # yes, stop here
+                continue
+            except astroid.NotFoundError:
+                pass
+            # is it an instance attribute of a parent class ?
+            try:
+                next(node.instance_attr_ancestors(attr))
+                # yes, stop here
+                continue
+            except StopIteration:
+                pass
+            # is it an instance attribute ?
+            try:
+                defstmts = node.instance_attr(attr)
+            except astroid.NotFoundError:
+                pass
+            else:
+                # filter out augment assignment nodes
+                defstmts = [stmt for stmt in defstmts if stmt not in nodes]
+                if not defstmts:
+                    # only augment assignment for this node, no-member should be
+                    # triggered by the typecheck checker
+                    continue
+                # filter defstmts to only pick the first one when there are
+                # several assignments in the same scope
+                scope = defstmts[0].scope()
+                defstmts = [stmt for i, stmt in enumerate(defstmts)
+                            if i == 0 or stmt.scope() is not scope]
+                # if there are still more than one, don't attempt to be smarter
+                # than we can be
+                if len(defstmts) == 1:
+                    defstmt = defstmts[0]
+                    # check that if the node is accessed in the same method as
+                    # it's defined, it's accessed after the initial assignment
+                    frame = defstmt.frame()
+                    lno = defstmt.fromlineno
+                    for _node in nodes:
+                        if _node.frame() is frame and _node.fromlineno < lno \
+                           and not are_exclusive(_node.statement(), defstmt,
+                                                 ('AttributeError', 'Exception', 'BaseException')):
+                            self.add_message('access-member-before-definition',
+                                             node=_node, args=(attr, lno))
+
+    def _check_first_arg_for_type(self, node, metaclass=0):
+        """check the name of first argument, expect:
+
+        * 'self' for a regular method
+        * 'cls' for a class method or a metaclass regular method (actually
+          valid-classmethod-first-arg value)
+        * 'mcs' for a metaclass class method (actually
+          valid-metaclass-classmethod-first-arg)
+        * not one of the above for a static method
+        """
+        # don't care about functions with unknown argument (builtins)
+        if node.args.args is None:
+            return
+        first_arg = node.args.args and node.argnames()[0]
+        self._first_attrs.append(first_arg)
+        first = self._first_attrs[-1]
+        # static method
+        if node.type == 'staticmethod':
+            if (first_arg == 'self' or
+                    first_arg in self.config.valid_classmethod_first_arg or
+                    first_arg in self.config.valid_metaclass_classmethod_first_arg):
+                self.add_message('bad-staticmethod-argument', args=first, node=node)
+                return
+            self._first_attrs[-1] = None
+        # class / regular method with no args
+        elif not node.args.args:
+            self.add_message('no-method-argument', node=node)
+        # metaclass
+        elif metaclass:
+            # metaclass __new__ or classmethod
+            if node.type == 'classmethod':
+                self._check_first_arg_config(
+                    first,
+                    self.config.valid_metaclass_classmethod_first_arg, node,
+                    'bad-mcs-classmethod-argument', node.name)
+            # metaclass regular method
+            else:
+                self._check_first_arg_config(
+                    first,
+                    self.config.valid_classmethod_first_arg, node,
+                    'bad-mcs-method-argument',
+                    node.name)
+        # regular class
+        else:
+            # class method
+            if node.type == 'classmethod':
+                self._check_first_arg_config(
+                    first,
+                    self.config.valid_classmethod_first_arg, node,
+                    'bad-classmethod-argument',
+                    node.name)
+            # regular method without self as argument
+            elif first != 'self':
+                self.add_message('no-self-argument', node=node)
+
+    def _check_first_arg_config(self, first, config, node, message,
+                                method_name):
+        if first not in config:
+            if len(config) == 1:
+                valid = repr(config[0])
+            else:
+                valid = ', '.join(repr(v) for v in config[:-1])
+                valid = '%s or %r' % (valid, config[-1])
+            self.add_message(message, args=(method_name, valid), node=node)
+
+    def _check_bases_classes(self, node):
+        """check that the given class node implements abstract methods from
+        base classes
+        """
+        def is_abstract(method):
+            return method.is_abstract(pass_is_abstract=False)
+
+        # check if this class abstract
+        if class_is_abstract(node):
+            return
+
+        methods = sorted(
+            unimplemented_abstract_methods(node, is_abstract).items(),
+            key=lambda item: item[0],
+        )
+        for name, method in methods:
+            owner = method.parent.frame()
+            if owner is node:
+                continue
+            # owner is not this class, it must be a parent class
+            # check that the ancestor's method is not abstract
+            if name in node.locals:
+                # it is redefined as an attribute or with a descriptor
+                continue
+            self.add_message('abstract-method', node=node,
+                             args=(name, owner.name))
+
+    def _check_interfaces(self, node):
+        """check that the given class node really implements declared
+        interfaces
+        """
+        e0221_hack = [False]
+        def iface_handler(obj):
+            """filter interface objects, it should be classes"""
+            if not isinstance(obj, astroid.Class):
+                e0221_hack[0] = True
+                self.add_message('interface-is-not-class', node=node,
+                                 args=(obj.as_string(),))
+                return False
+            return True
+        ignore_iface_methods = self.config.ignore_iface_methods
+        try:
+            for iface in node.interfaces(handler_func=iface_handler):
+                for imethod in iface.methods():
+                    name = imethod.name
+                    if name.startswith('_') or name in ignore_iface_methods:
+                        # don't check method beginning with an underscore,
+                        # usually belonging to the interface implementation
+                        continue
+                    # get class method astroid
+                    try:
+                        method = node_method(node, name)
+                    except astroid.NotFoundError:
+                        self.add_message('missing-interface-method',
+                                         args=(name, iface.name),
+                                         node=node)
+                        continue
+                    # ignore inherited methods
+                    if method.parent.frame() is not node:
+                        continue
+                    # check signature
+                    self._check_signature(method, imethod,
+                                          '%s interface' % iface.name)
+        except astroid.InferenceError:
+            if e0221_hack[0]:
+                return
+            implements = Instance(node).getattr('__implements__')[0]
+            assignment = implements.parent
+            assert isinstance(assignment, astroid.Assign)
+            # assignment.expr can be a Name or a Tuple or whatever.
+            # Use as_string() for the message
+            # FIXME: in case of multiple interfaces, find which one could not
+            #        be resolved
+            self.add_message('unresolved-interface', node=implements,
+                             args=(node.name, assignment.value.as_string()))
+
+    def _check_init(self, node):
+        """check that the __init__ method call super or ancestors'__init__
+        method
+        """
+        if (not self.linter.is_message_enabled('super-init-not-called') and
+                not self.linter.is_message_enabled('non-parent-init-called')):
+            return
+        klass_node = node.parent.frame()
+        to_call = _ancestors_to_call(klass_node)
+        not_called_yet = dict(to_call)
+        for stmt in node.nodes_of_class(astroid.CallFunc):
+            expr = stmt.func
+            if not isinstance(expr, astroid.Getattr) \
+                   or expr.attrname != '__init__':
+                continue
+            # skip the test if using super
+            if isinstance(expr.expr, astroid.CallFunc) and \
+                   isinstance(expr.expr.func, astroid.Name) and \
+               expr.expr.func.name == 'super':
+                return
+            try:
+                for klass in expr.expr.infer():
+                    if klass is YES:
+                        continue
+                    # The infered klass can be super(), which was
+                    # assigned to a variable and the `__init__`
+                    # was called later.
+                    #
+                    # base = super()
+                    # base.__init__(...)
+
+                    if (isinstance(klass, astroid.Instance) and
+                            isinstance(klass._proxied, astroid.Class) and
+                            is_builtin_object(klass._proxied) and
+                            klass._proxied.name == 'super'):
+                        return
+                    try:
+                        del not_called_yet[klass]
+                    except KeyError:
+                        if klass not in to_call:
+                            self.add_message('non-parent-init-called',
+                                             node=expr, args=klass.name)
+            except astroid.InferenceError:
+                continue
+        for klass, method in six.iteritems(not_called_yet):
+            if klass.name == 'object' or method.parent.name == 'object':
+                continue
+            self.add_message('super-init-not-called', args=klass.name, node=node)
+
+    def _check_signature(self, method1, refmethod, class_type):
+        """check that the signature of the two given methods match
+
+        class_type is in 'class', 'interface'
+        """
+        if not (isinstance(method1, astroid.Function)
+                and isinstance(refmethod, astroid.Function)):
+            self.add_message('method-check-failed',
+                             args=(method1, refmethod), node=method1)
+            return
+        # don't care about functions with unknown argument (builtins)
+        if method1.args.args is None or refmethod.args.args is None:
+            return
+        # if we use *args, **kwargs, skip the below checks
+        if method1.args.vararg or method1.args.kwarg:
+            return
+        if is_attr_private(method1.name):
+            return
+        if len(method1.args.args) != len(refmethod.args.args):
+            self.add_message('arguments-differ',
+                             args=(class_type, method1.name),
+                             node=method1)
+        elif len(method1.args.defaults) < len(refmethod.args.defaults):
+            self.add_message('signature-differs',
+                             args=(class_type, method1.name),
+                             node=method1)
+
+    def is_first_attr(self, node):
+        """Check that attribute lookup name use first attribute variable name
+        (self for method, cls for classmethod and mcs for metaclass).
+        """
+        return self._first_attrs and isinstance(node.expr, astroid.Name) and \
+                   node.expr.name == self._first_attrs[-1]
+
+def _ancestors_to_call(klass_node, method='__init__'):
+    """return a dictionary where keys are the list of base classes providing
+    the queried method, and so that should/may be called from the method node
+    """
+    to_call = {}
+    for base_node in klass_node.ancestors(recurs=False):
+        try:
+            to_call[base_node] = next(base_node.igetattr(method))
+        except astroid.InferenceError:
+            continue
+    return to_call
+
+
+def node_method(node, method_name):
+    """get astroid for <method_name> on the given class node, ensuring it
+    is a Function node
+    """
+    for n in node.local_attr(method_name):
+        if isinstance(n, astroid.Function):
+            return n
+    raise astroid.NotFoundError(method_name)
+
+def register(linter):
+    """required method to auto register this checker """
+    linter.register_checker(ClassChecker(linter))