path: root/scoped_nodes.py

# 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.,
# 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
"""This module extends ast "scoped" node, i.e. which are opening a new
local scope in the language definition : Module, Class, Function (and
Lambda and GenExpr to some extends).

All new methods and attributes added on each class are documented
below.


:author:    Sylvain Thenault
:copyright: 2003-2009 LOGILAB S.A. (Paris, FRANCE)
:contact:   http://www.logilab.fr/ -- mailto:python-projects@logilab.org
:copyright: 2003-2009 Sylvain Thenault
:contact:   mailto:thenault@gmail.com
"""
from __future__ import generators

__doctype__ = "restructuredtext en"

import __builtin__
import sys

from logilab.common.compat import chain, set
from logilab.common.decorators import cached

from logilab.astng import MANAGER, NotFoundError, NoDefault, \
     ASTNGBuildingException, InferenceError
from logilab.astng.node_classes import (Const, Dict, From, List, Pass,
     Raise, Return, Tuple, Yield, DelAttr, are_exclusive, const_factory as cf,
     unpack_infer) 
from logilab.astng._nodes import NodeNG, StmtMixIn, BaseClass
from logilab.astng.infutils import YES, InferenceContext, Instance, Generator, \
     UnboundMethod, _infer_stmts, copy_context

from logilab.astng.nodes_as_string import as_string


def remove_nodes(func, cls):
    def wrapper(*args, **kwargs):
        nodes = [n for n in func(*args, **kwargs) if not isinstance(n, cls)]
        if not nodes:
            raise NotFoundError()
        return nodes
    return wrapper

def function_to_unbound_method(func):
    def wrapper(*args, **kwargs):
        return [isinstance(n, Function) and UnboundMethod(n) or n
                for n in func(*args, **kwargs)]
    return wrapper


def std_special_attributes(self, name, add_locals=True):
    if add_locals:
        locals = self.locals
    else:
        locals = {}
    if name == '__name__':
        return [cf(self.name)] + locals.get(name, [])
    if name == '__doc__':
        return [cf(self.doc)] + locals.get(name, [])
    if name == '__dict__':
        return [Dict()] + locals.get(name, [])
    raise NotFoundError(name)


# MixIns -----------------------------------------------------



class LookupMixIn(BaseClass):
    """Mixin looking up a name in the right scope
    """

    def lookup(self, name):
        """lookup a variable name

        return the scope node and the list of assignments associated to the given
        name according to the scope where it has been found (locals, globals or
        builtin)

        The lookup is starting from self's scope. If self is not a frame itself and
        the name is found in the inner frame locals, statements will be filtered
        to remove ignorable statements according to self's location
        """
        return self.scope().scope_lookup(self, name)

    def ilookup(self, name, context=None):
        """infered lookup

        return an iterator on infered values of the statements returned by
        the lookup method
        """
        frame, stmts = self.lookup(name)
        context = copy_context(context)
        context.lookupname = name
        return _infer_stmts(stmts, context, frame)

    def _filter_stmts(self, stmts, frame, offset):
        """filter statements to remove ignorable statements.

        If self is not a frame itself and the name is found in the inner
        frame locals, statements will be filtered to remove ignorable
        statements according to self's location
        """
        # if offset == -1, my actual frame is not the inner frame but its parent
        #
        # class A(B): pass
        #
        # we need this to resolve B correctly
        if offset == -1:
            myframe = self.frame().parent.frame()
        else:
            myframe = self.frame()
        if not myframe is frame or self is frame:
            return stmts
        mystmt = self.statement()
        # line filtering if we are in the same frame
        #
        # take care node may be missing lineno information (this is the case for
        # nodes inserted for living objects)
        if myframe is frame and mystmt.fromlineno is not None:
            assert mystmt.fromlineno is not None, mystmt
            mylineno = mystmt.fromlineno + offset
        else:
            # disabling lineno filtering
            mylineno = 0
        _stmts = []
        _stmt_parents = []
        for node in stmts:
            stmt = node.statement()
            # line filtering is on and we have reached our location, break
            if mylineno > 0 and stmt.fromlineno > mylineno:
                break
            if isinstance(node, nodes.Class) and self in node.bases:
                break
            assert hasattr(node, 'ass_type'), (node, node.scope(),
                                               node.scope().locals)
            ass_type = node.ass_type()
            if ass_type is mystmt and not isinstance(ass_type, (nodes.Class,
                    nodes.Function, nodes.Import, nodes.From, nodes.Lambda)):
                if not isinstance(ass_type, nodes.Comprehension):
                    break
                if isinstance(self, (nodes.Const, nodes.Name)):
                    _stmts = [self]
                    break
            elif ass_type.statement() is mystmt:
                # original node's statement is the assignment, only keeps
                # current node (gen exp, list comp)
                _stmts = [node]
                break        
            optional_assign = isinstance(ass_type, (nodes.For, nodes.Comprehension))
            if optional_assign and ass_type.parent_of(self):
                # we are inside a loop, loop var assigment is hidding previous
                # assigment
                _stmts = [node]
                _stmt_parents = [stmt.parent]
                continue
            # XXX comment various branches below!!!
            try:
                pindex = _stmt_parents.index(stmt.parent)
            except ValueError:
                pass
            else:
                # we got a parent index, this means the currently visited node
                # is at the same block level as a previously visited node
                if _stmts[pindex].ass_type().parent_of(ass_type):
                    # both statements are not at the same block level
                    continue
                # if currently visited node is following previously considered
                # assignement and both are not exclusive, we can drop the
                # previous one. For instance in the following code ::
                #
                #   if a:
                #     x = 1
                #   else:
                #     x = 2
                #   print x
                #
                # we can't remove neither x = 1 nor x = 2 when looking for 'x'
                # of 'print x'; while in the following ::
                #
                #   x = 1
                #   x = 2
                #   print x
                #
                # we can remove x = 1 when we see x = 2
                #
                # moreover, on loop assignment types, assignment won't
                # necessarily be done if the loop has no iteration, so we don't
                # want to clear previous assigments if any (hence the test on
                # optional_assign)
                if not (optional_assign or are_exclusive(_stmts[pindex], node)):
                    del _stmt_parents[pindex]
                    del _stmts[pindex]
            if isinstance(node, nodes.AssName):
                if not optional_assign and stmt.parent is mystmt.parent:
                    _stmts = []
                    _stmt_parents = []
            elif isinstance(node, nodes.DelName):
                _stmts = []
                _stmt_parents = []
                continue
            if not are_exclusive(self, node):
                _stmts.append(node)
                _stmt_parents.append(stmt.parent)
        return _stmts


def builtin_lookup(name):
    """lookup a name into the builtin module
    return the list of matching statements and the astng for the builtin
    module
    """
    builtinastng = MANAGER.astng_from_module(__builtin__)
    if name == '__dict__':
        return builtinastng, ()
    try:
        stmts = builtinastng.locals[name]
    except KeyError:
        stmts = ()
    return builtinastng, stmts


class LocalsDictNodeNG(LookupMixIn, NodeNG):
    """ this class provides locals handling common to Module, Function
    and Class nodes, including a dict like interface for direct access
    to locals information
    """

    # attributes below are set by the builder module or by raw factories

    # dictionary of locals with name as key and node defining the local as
    # value
    locals = None

    def qname(self):
        """return the 'qualified' name of the node, eg module.name,
        module.class.name ...
        """
        if self.parent is None:
            return self.name
        return '%s.%s' % (self.parent.frame().qname(), self.name)

    def frame(self):
        """return the first parent frame node (i.e. Module, Function or Class)
        """
        return self

    def scope(self):
        """return the first node defining a new scope (i.e. Module,
        Function, Class, Lambda but also GenExpr)
        """
        return self


    def _scope_lookup(self, node, name, offset=0):
        """XXX method for interfacing the scope lookup"""
        try:
            stmts = node._filter_stmts(self.locals[name], self, offset)
        except KeyError:
            stmts = ()
        if stmts:
            return self, stmts
        if self.parent: # i.e. not Module
            # nested scope: if parent scope is a function, that's fine
            # else jump to the module
            pscope = self.parent.scope()
            if not isinstance(pscope, nodes.Function):
                pscope = pscope.root()
            return pscope.scope_lookup(node, name)
        return builtin_lookup(name) # Module



    def set_local(self, name, stmt):
        """define <name> in locals (<stmt> is the node defining the name)
        if the node is a Module node (i.e. has globals), add the name to
        globals

        if the name is already defined, ignore it
        """
        assert self.locals is not None, (self, id(self))
        #assert not stmt in self.locals.get(name, ()), (self, stmt)
        self.locals.setdefault(name, []).append(stmt)

    __setitem__ = set_local

    def _append_node(self, child):
        """append a child, linking it in the tree"""
        self.body.append(child)
        child.parent = self

    def add_local_node(self, child_node, name=None):
        """append a child which should alter locals to the given node"""
        if name != '__class__':
            # add __class__ node as a child will cause infinite recursion later!
            self._append_node(child_node)
        self.set_local(name or child_node.name, child_node)


    def __getitem__(self, item):
        """method from the `dict` interface returning the first node
        associated with the given name in the locals dictionary

        :type item: str
        :param item: the name of the locally defined object
        :raises KeyError: if the name is not defined
        """
        return self.locals[item][0]

    def __iter__(self):
        """method from the `dict` interface returning an iterator on
        `self.keys()`
        """
        return iter(self.keys())

    def keys(self):
        """method from the `dict` interface returning a tuple containing
        locally defined names
        """
        return self.locals.keys()

    def values(self):
        """method from the `dict` interface returning a tuple containing
        locally defined nodes which are instance of `Function` or `Class`
        """
        return [self[key] for key in self.keys()]

    def items(self):
        """method from the `dict` interface returning a list of tuple
        containing each locally defined name with its associated node,
        which is an instance of `Function` or `Class`
        """
        return zip(self.keys(), self.values())

    def has_key(self, name):
        """method from the `dict` interface returning True if the given
        name is defined in the locals dictionary
        """
        return self.locals.has_key(name)

    __contains__ = has_key

# Name classses

class AssName(LookupMixIn, NodeNG):
    """class representing an AssName node"""


class DelName(LookupMixIn, NodeNG):
    """class representing a DelName node"""


class Name(LookupMixIn, NodeNG):
    """class representing a Name node"""


# Module  #####################################################################

class Module(LocalsDictNodeNG):
    """/!\ this class should not be used directly /!\
    It is only used as an additionnal base class for the original class.
    """
    fromlineno = 0
    lineno = 0

    # attributes below are set by the builder module or by raw factories

    # the file from which as been extracted the astng representation. It may
    # be None if the representation has been built from a built-in module
    file = None
    # the module name
    name = None
    # boolean for astng built from source (i.e. ast)
    pure_python = None
    # boolean for package module
    package = None
    # dictionary of globals with name as key and node defining the global
    # as value
    globals = None

    # names of python special attributes (handled by getattr impl.)
    special_attributes = set(('__name__', '__doc__', '__file__', '__path__',
                              '__dict__'))
    # names of module attributes available through the global scope
    scope_attrs = set(('__name__', '__doc__', '__file__', '__path__'))

    # Module is not a Statement node but needs the replace method (see StmtMixIn)
    def replace(self, child, newchild):
        sequence = self.child_sequence(child)
        newchild.parent = self
        child.parent = None
        sequence[sequence.index(child)] = newchild

    def block_range(self, lineno):
        """return block line numbers.

        start from the "class" position whatever the given lineno
        """
        return self.fromlineno, self.tolineno

    def scope_lookup(self, node, name, offset=0):
        if name in self.scope_attrs and not name in self.locals:
            try:
                return self, self.getattr(name)
            except NotFoundError:
                return self, ()
        return self._scope_lookup(node, name, offset)

    def pytype(self):
        return '__builtin__.module'

    def getattr(self, name, context=None):
        if not name in self.special_attributes:
            try:
                return self.locals[name]
            except KeyError:
                pass
        else:
            if name == '__file__':
                return [cf(self.file)] + self.locals.get(name, [])
            if name == '__path__':
                if self.package:
                    return [List()] + self.locals.get(name, [])
            return std_special_attributes(self, name)
        if self.package:
            try:
                return [self.import_module(name, relative_only=True)]
            except (KeyboardInterrupt, SystemExit):
                raise
            except:
                pass
        raise NotFoundError(name)
    getattr = remove_nodes(getattr, DelName)

    def igetattr(self, name, context=None):
        """inferred getattr"""
        # set lookup name since this is necessary to infer on import nodes for
        # instance
        context = copy_context(context)
        context.lookupname = name
        try:
            return _infer_stmts(self.getattr(name, context), context, frame=self)
        except NotFoundError:
            raise InferenceError(name)

    def fully_defined(self):
        """return True if this module has been built from a .py file
        and so contains a complete representation including the code
        """
        return self.file is not None and self.file.endswith('.py')

    def statement(self):
        """return the first parent node marked as statement node
        consider a module as a statement...
        """
        return self

    def previous_sibling(self):
        """module has no sibling"""
        return

    def next_sibling(self):
        """module has no sibling"""
        return

    def absolute_import_activated(self):
        for stmt in self.locals.get('absolute_import', ()):
            if isinstance(stmt, From) and stmt.modname == '__future__':
                return True
        return False

    def import_module(self, modname, relative_only=False, level=None):
        """import the given module considering self as context"""
        try:
            absmodname = self.absolute_modname(modname, level)
            return MANAGER.astng_from_module_name(absmodname)
        except ASTNGBuildingException:
            # we only want to import a sub module or package of this module,
            # skip here
            if relative_only:
                raise
        module = MANAGER.astng_from_module_name(modname)
        return module

    def absolute_modname(self, modname, level):
        if self.absolute_import_activated() and not level:
            return modname
        if level:
            parts = self.name.split('.')
            if self.package:
                parts.append('__init__')
            package_name = '.'.join(parts[:-level])
        elif self.package:
            package_name = self.name
        else:
            package_name = '.'.join(self.name.split('.')[:-1])
        if package_name:
            return '%s.%s' % (package_name, modname)
        return modname

    def wildcard_import_names(self):
        """return the list of imported names when this module is 'wildcard
        imported'

        It doesn't include the '__builtins__' name which is added by the
        current CPython implementation of wildcard imports.
        """
        # take advantage of a living module if it exists
        try:
            living = sys.modules[self.name]
        except KeyError:
            pass
        else:
            try:
                return living.__all__
            except AttributeError:
                return [name for name in living.__dict__.keys()
                        if not name.startswith('_')]
        # else lookup the astng
        #
        # We separate the different steps of lookup in try/excepts
        # to avoid catching too many Exceptions
        # However, we can not analyse dynamically constructed __all__
        try:
            all = self['__all__']
        except KeyError:
            return [name for name in self.keys() if not name.startswith('_')]
        try:
            explicit = all.assigned_stmts().next()
        except InferenceError:
            return [name for name in self.keys() if not name.startswith('_')]
        try:
            # should be a Tuple/List of constant string / 1 string not allowed
            return [const.value for const in explicit.elts]
        except AttributeError:
            return [name for name in self.keys() if not name.startswith('_')]


class GenExpr(LocalsDictNodeNG):
    """/!\ this class should not be used directly /!\
    It is only used as an additionnal base class for the original class.
    """

    def frame(self):
        return self.parent.frame()
GenExpr.scope_lookup = LocalsDictNodeNG._scope_lookup


# Function  ###################################################################

class Lambda(LocalsDictNodeNG):
    """/!\ this class should not be used directly /!\
    It is only used as an additionnal base class for the original class.
    """

    # function's type, 'function' | 'method' | 'staticmethod' | 'classmethod'
    type = 'function'

    def pytype(self):
        if 'method' in self.type:
            return '__builtin__.instancemethod'
        return '__builtin__.function'

    def callable(self):
        return True

    def argnames(self):
        """return a list of argument names"""
        if self.args.args: # maybe None with builtin functions
            names = _rec_get_names(self.args.args)
        else:
            names = []
        if self.args.vararg:
            names.append(self.args.vararg)
        if self.args.kwarg:
            names.append(self.args.kwarg)
        return names

    def infer_call_result(self, caller, context=None):
        """infer what a function is returning when called"""
        return self.body.infer(context)

    def scope_lookup(self, node, name, offset=0):
        if node in self.args.defaults:
            frame = self.parent.frame()
            # line offset to avoid that def func(f=func) resolve the default
            # value to the defined function
            offset = -1
        else:
            # check this is not used in function decorators
            frame = self
        return frame._scope_lookup(node, name, offset)


class Function(StmtMixIn, Lambda):
    """/!\ this class should not be used directly /!\
    It is only used as an additionnal base class for the original class.
    """

    special_attributes = set(('__name__', '__doc__', '__dict__'))
    # attributes below are set by the builder module or by raw factories

    blockstart_tolineno = None

    def set_line_info(self, lastchild):
        self.fromlineno = self.lineno
        # lineno is the line number of the first decorator, we want the def statement lineno
        if self.decorators is not None:
            self.fromlineno += len(self.decorators.nodes)
        self.tolineno = lastchild.tolineno
        self.blockstart_tolineno = self.args.tolineno

    def block_range(self, lineno):
        """return block line numbers.

        start from the "class" position whatever the given lineno
        """
        return self.fromlineno, self.tolineno

    def getattr(self, name, context=None):
        """this method doesn't look in the instance_attrs dictionary since it's
        done by an Instance proxy at inference time.
        """
        if name == '__module__':
            return [cf(self.root().qname())]
        return std_special_attributes(self, name, False)

    def is_method(self):
        """return true if the function node should be considered as a method"""
        # check we are defined in a Class, because this is usually expected
        # (e.g. pylint...) when is_method() return True
        return self.type != 'function' and isinstance(self.parent.frame(), Class)

    @cached
    def decoratornames(self):
        """return a list of decorator qualified names"""
        result = set()
        decoratornodes = []
        if self.decorators is not None:
            decoratornodes += self.decorators.nodes
        decoratornodes += getattr(self, 'extra_decorators', [])
        for decnode in decoratornodes:
            for infnode in decnode.infer():
                result.add(infnode.qname())
        return result


    def is_bound(self):
        """return true if the function is bound to an Instance or a class"""
        return self.type == 'classmethod'

    def is_abstract(self, pass_is_abstract=True):
        """return true if the method is abstract
        It's considered as abstract if the only statement is a raise of
        NotImplementError, or, if pass_is_abstract, a pass statement
        """
        for child_node in self.body:
            if isinstance(child_node, Raise) and child_node.type:
                try:
                    name = child_node.type.nodes_of_class(Name).next()
                    if name.name == 'NotImplementedError':
                        return True
                except StopIteration:
                    pass
            if pass_is_abstract and isinstance(child_node, Pass):
                return True
            return False
        # empty function is the same as function with a single "pass" statement
        if pass_is_abstract:
            return True

    def is_generator(self):
        """return true if this is a generator function"""
        # XXX should be flagged, not computed
        try:
            return self.nodes_of_class(Yield, skip_klass=Function).next()
        except StopIteration:
            return False

    def infer_call_result(self, caller, context=None):
        """infer what a function is returning when called"""
        if self.is_generator():
            yield Generator(self)
            return
        returns = self.nodes_of_class(Return, skip_klass=Function)
        for returnnode in returns:
            if returnnode.value is None:
                yield None
            else:
                try:
                    for infered in returnnode.value.infer(context):
                        yield infered
                except InferenceError:
                    yield YES



def _rec_get_names(args, names=None):
    """return a list of all argument names"""
    if names is None:
        names = []
    for arg in args:
        if isinstance(arg, Tuple):
            _rec_get_names(arg.elts, names)
        else:
            names.append(arg.name)
    return names


def _format_args(args, defaults=None):
    values = []
    if args is None:
        return ''
    if defaults is not None:
        default_offset = len(args) - len(defaults)
    for i, arg in enumerate(args):
        if isinstance(arg, Tuple):
            values.append('(%s)' % _format_args(arg.elts))
        else:
            values.append(arg.name)
            if defaults is not None and i >= default_offset:
                values[-1] += '=' + defaults[i-default_offset].as_string()
    return ', '.join(values)


# Class ######################################################################

def _class_type(klass):
    """return a Class node type to differ metaclass, interface and exception
    from 'regular' classes
    """
    if klass._type is not None:
        return klass._type
    if klass.name == 'type':
        klass._type = 'metaclass'
    elif klass.name.endswith('Interface'):
        klass._type = 'interface'
    elif klass.name.endswith('Exception'):
        klass._type = 'exception'
    else:
        for base in klass.ancestors(recurs=False):
            if base.type != 'class':
                klass._type = base.type
                break
    if klass._type is None:
        klass._type = 'class'
    return klass._type

def _iface_hdlr(iface_node):
    """a handler function used by interfaces to handle suspicious
    interface nodes
    """
    return True


class Class(StmtMixIn, LocalsDictNodeNG):
    """/!\ this class should not be used directly /!\
    It is only used as an additionnal base class for the original class.
    """

    special_attributes = set(('__name__', '__doc__', '__dict__', '__module__',
                              '__bases__', '__mro__'))

    blockstart_tolineno = None

    _type = None
    type = property(_class_type,
                    doc="class'type, possible values are 'class' | "
                    "'metaclass' | 'interface' | 'exception'")

    def _newstyle_impl(self, context=None):
        if context is None:
            context = InferenceContext()
        if self._newstyle is not None:
            return self._newstyle
        for base in self.ancestors(recurs=False, context=context):
            if base._newstyle_impl(context):
                self._newstyle = True
                break
        if self._newstyle is None:
            self._newstyle = False
        return self._newstyle

    _newstyle = None
    newstyle = property(_newstyle_impl,
                        doc="boolean indicating if it's a new style class"
                        "or not")

    def set_line_info(self, lastchild):
        self.fromlineno = self.lineno
        self.blockstart_tolineno = self.bases and self.bases[-1].tolineno or self.fromlineno
        if lastchild is not None:
            self.tolineno = lastchild.tolineno
        # else this is a class with only a docstring, then tolineno is (should be) already ok

    def block_range(self, lineno):
        """return block line numbers.

        start from the "class" position whatever the given lineno
        """
        return self.fromlineno, self.tolineno

    def pytype(self):
        if self.newstyle:
            return '__builtin__.type'
        return '__builtin__.classobj'

    def callable(self):
        return True

    def infer_call_result(self, caller, context=None):
        """infer what a class is returning when called"""
        yield Instance(self)

    def scope_lookup(self, node, name, offset=0):
        if node in self.bases:
            frame = self.parent.frame()
            # line offset to avoid that class A(A) resolve the ancestor to
            # the defined class
            offset = -1
        else:
            frame = self
        return frame._scope_lookup(node, name, offset)

    # attributes below are set by the builder module or by raw factories

    # a dictionary of class instances attributes
    instance_attrs = None

    # list of parent class as a list of string (i.e. names as they appears
    # in the class definition) XXX bw compat
    def basenames(self):
        return [as_string(bnode) for bnode in self.bases]
    basenames = property(basenames)

    def ancestors(self, recurs=True, context=None):
        """return an iterator on the node base classes in a prefixed
        depth first order

        :param recurs:
          boolean indicating if it should recurse or return direct
          ancestors only
        """
        # FIXME: should be possible to choose the resolution order
        # XXX inference make infinite loops possible here (see BaseTransformer
        # manipulation in the builder module for instance !)
        if context is None:
            context = InferenceContext()
        for stmt in self.bases:
            try:
                for baseobj in stmt.infer(context):
                    if not isinstance(baseobj, Class):
                        # duh ?
                        continue
                    if baseobj is self:
                        continue # cf xxx above
                    yield baseobj
                    if recurs:
                        for grandpa in baseobj.ancestors(True, context):
                            if grandpa is self:
                                continue # cf xxx above
                            yield grandpa
            except InferenceError:
                # XXX log error ?
                continue

    def local_attr_ancestors(self, name, context=None):
        """return an iterator on astng representation of parent classes
        which have <name> defined in their locals
        """
        for astng in self.ancestors(context=context):
            if astng.locals.has_key(name):
                yield astng

    def instance_attr_ancestors(self, name, context=None):
        """return an iterator on astng representation of parent classes
        which have <name> defined in their instance attribute dictionary
        """
        for astng in self.ancestors(context=context):
            if astng.instance_attrs.has_key(name):
                yield astng

    def local_attr(self, name, context=None):
        """return the list of assign node associated to name in this class
        locals or in its parents

        :raises `NotFoundError`:
          if no attribute with this name has been find in this class or
          its parent classes
        """
        try:
            return self.locals[name]
        except KeyError:
            # get if from the first parent implementing it if any
            for class_node in self.local_attr_ancestors(name, context):
                return class_node.locals[name]
        raise NotFoundError(name)
    local_attr = remove_nodes(local_attr, DelAttr)

    def instance_attr(self, name, context=None):
        """return the astng nodes associated to name in this class instance
        attributes dictionary and in its parents

        :raises `NotFoundError`:
          if no attribute with this name has been find in this class or
          its parent classes
        """
        values = self.instance_attrs.get(name, [])
        # get if from the first parent implementing it if any
        for class_node in self.instance_attr_ancestors(name, context):
            values += class_node.instance_attrs[name]
        if not values:
            raise NotFoundError(name)
        return values
    instance_attr = remove_nodes(instance_attr, DelAttr)

    def getattr(self, name, context=None):
        """this method doesn't look in the instance_attrs dictionary since it's
        done by an Instance proxy at inference time.

        It may return a YES object if the attribute has not been actually
        found but a __getattr__ or __getattribute__ method is defined
        """
        values = self.locals.get(name, [])
        if name in self.special_attributes:
            if name == '__module__':
                return [cf(self.root().qname())] + values
            if name == '__bases__':
                return [cf(tuple(self.ancestors(recurs=False, context=context)))] + values
            # XXX need proper meta class handling + MRO implementation
            if name == '__mro__' and self.newstyle:
                # XXX mro is read-only but that's not our job to detect that
                return [cf(tuple(self.ancestors(recurs=True, context=context)))] + values
            return std_special_attributes(self, name)
        # don't modify the list in self.locals!
        values = list(values)
        for classnode in self.ancestors(recurs=False, context=context):
            try:
                values += classnode.getattr(name, context)
            except NotFoundError:
                continue
        if not values:
            raise NotFoundError(name)
        return values
    getattr = function_to_unbound_method(remove_nodes(getattr, DelAttr))

    def igetattr(self, name, context=None):
        """inferred getattr, need special treatment in class to handle
        descriptors
        """
        # set lookup name since this is necessary to infer on import nodes for
        # instance
        context = copy_context(context)
        context.lookupname = name
        try:
            for infered in _infer_stmts(self.getattr(name, context), context,
                                        frame=self):
                # yield YES object instead of descriptors when necessary
                if not isinstance(infered, Const) and isinstance(infered, Instance):
                    try:
                        infered._proxied.getattr('__get__', context)
                    except NotFoundError:
                        yield infered
                    else:
                        yield YES
                else:
                    yield infered
        except NotFoundError:
            if not name.startswith('__') and self.has_dynamic_getattr(context):
                # class handle some dynamic attributes, return a YES object
                yield YES
            else:
                raise InferenceError(name)

    def has_dynamic_getattr(self, context=None):
        """return True if the class has a custom __getattr__ or
        __getattribute__ method
        """
        # need to explicitly handle optparse.Values (setattr is not detected)
        if self.name == 'Values' and self.root().name == 'optparse':
            return True
        try:
            self.getattr('__getattr__', context)
            return True
        except NotFoundError:
            #if self.newstyle: XXX cause an infinite recursion error
            try:
                getattribute = self.getattr('__getattribute__', context)[0]
                if getattribute.root().name != '__builtin__':
                    # class has a custom __getattribute__ defined
                    return True
            except NotFoundError:
                pass
        return False

    def methods(self):
        """return an iterator on all methods defined in the class and
        its ancestors
        """
        done = {}
        for astng in chain(iter((self,)), self.ancestors()):
            for meth in astng.mymethods():
                if done.has_key(meth.name):
                    continue
                done[meth.name] = None
                yield meth

    def mymethods(self):
        """return an iterator on all methods defined in the class"""
        for member in self.values():
            if isinstance(member, Function):
                yield member

    def interfaces(self, herited=True, handler_func=_iface_hdlr):
        """return an iterator on interfaces implemented by the given
        class node
        """
        # FIXME: what if __implements__ = (MyIFace, MyParent.__implements__)...
        try:
            implements = Instance(self).getattr('__implements__')[0]
        except NotFoundError:
            return
        if not herited and not implements.frame() is self:
            return
        found = set()
        for iface in unpack_infer(implements):
            if iface is YES:
                continue
            if not iface in found and handler_func(iface):
                found.add(iface)
                yield iface
        if not found:
            raise InferenceError()