python-astroid 1.4.9-1 / usr / lib / python2.7 / dist-packages / astroid / bases.py

# copyright 2003-2013 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of astroid.
#
# astroid is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation, either version 2.1 of the License, or (at your
# option) any later version.
#
# astroid 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 Lesser General Public License
# for more details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with astroid. If not, see <http://www.gnu.org/licenses/>.
"""This module contains base classes and functions for the nodes and some
inference utils.
"""
import functools
import sys
import warnings

import wrapt

from astroid import context as contextmod
from astroid import decorators as decoratorsmod
from astroid import exceptions
from astroid import util


if sys.version_info >= (3, 0):
    BUILTINS = 'builtins'
else:
    BUILTINS = '__builtin__'
PROPERTIES = {BUILTINS + '.property', 'abc.abstractproperty'}
# List of possible property names. We use this list in order
# to see if a method is a property or not. This should be
# pretty reliable and fast, the alternative being to check each
# decorator to see if its a real property-like descriptor, which
# can be too complicated.
# Also, these aren't qualified, because each project can
# define them, we shouldn't expect to know every possible
# property-like decorator!
# TODO(cpopa): just implement descriptors already.
POSSIBLE_PROPERTIES = {"cached_property", "cachedproperty",
                       "lazyproperty", "lazy_property", "reify",
                       "lazyattribute", "lazy_attribute",
                       "LazyProperty", "lazy"}


def _is_property(meth):
    if PROPERTIES.intersection(meth.decoratornames()):
        return True
    stripped = {name.split(".")[-1] for name in meth.decoratornames()
                if name is not util.YES}
    return any(name in stripped for name in POSSIBLE_PROPERTIES)


class Proxy(object):
    """a simple proxy object"""

    _proxied = None # proxied object may be set by class or by instance

    def __init__(self, proxied=None):
        if proxied is not None:
            self._proxied = proxied

    def __getattr__(self, name):
        if name == '_proxied':
            return getattr(self.__class__, '_proxied')
        if name in self.__dict__:
            return self.__dict__[name]
        return getattr(self._proxied, name)

    def infer(self, context=None):
        yield self


def _infer_stmts(stmts, context, frame=None):
    """Return an iterator on statements inferred by each statement in *stmts*."""
    stmt = None
    inferred = False
    if context is not None:
        name = context.lookupname
        context = context.clone()
    else:
        name = None
        context = contextmod.InferenceContext()

    for stmt in stmts:
        if stmt is util.YES:
            yield stmt
            inferred = True
            continue
        context.lookupname = stmt._infer_name(frame, name)
        try:
            for inferred in stmt.infer(context=context):
                yield inferred
                inferred = True
        except exceptions.UnresolvableName:
            continue
        except exceptions.InferenceError:
            yield util.YES
            inferred = True
    if not inferred:
        raise exceptions.InferenceError(str(stmt))


class Instance(Proxy):
    """a special node representing a class instance"""
    def getattr(self, name, context=None, lookupclass=True):
        try:
            values = self._proxied.instance_attr(name, context)
        except exceptions.NotFoundError:
            if name == '__class__':
                return [self._proxied]
            if lookupclass:
                # class attributes not available through the instance
                # unless they are explicitly defined
                if name in ('__name__', '__bases__', '__mro__', '__subclasses__'):
                    return self._proxied.local_attr(name)
                return self._proxied.getattr(name, context)
            raise exceptions.NotFoundError(name)
        # since we've no context information, return matching class members as
        # well
        if lookupclass:
            try:
                return values + self._proxied.getattr(name, context)
            except exceptions.NotFoundError:
                pass
        return values

    def igetattr(self, name, context=None):
        """inferred getattr"""
        if not context:
            context = contextmod.InferenceContext()
        try:
            # avoid recursively inferring the same attr on the same class
            context.push((self._proxied, name))
            # XXX frame should be self._proxied, or not ?
            get_attr = self.getattr(name, context, lookupclass=False)
            return _infer_stmts(
                self._wrap_attr(get_attr, context),
                context,
                frame=self,
            )
        except exceptions.NotFoundError:
            try:
                # fallback to class'igetattr since it has some logic to handle
                # descriptors
                return self._wrap_attr(self._proxied.igetattr(name, context),
                                       context)
            except exceptions.NotFoundError:
                raise exceptions.InferenceError(name)

    def _wrap_attr(self, attrs, context=None):
        """wrap bound methods of attrs in a InstanceMethod proxies"""
        for attr in attrs:
            if isinstance(attr, UnboundMethod):
                if _is_property(attr):
                    for inferred in attr.infer_call_result(self, context):
                        yield inferred
                else:
                    yield BoundMethod(attr, self)
            elif hasattr(attr, 'name') and attr.name == '<lambda>':
                # This is a lambda function defined at class level,
                # since its scope is the underlying _proxied class.
                # Unfortunately, we can't do an isinstance check here,
                # because of the circular dependency between astroid.bases
                # and astroid.scoped_nodes.
                if attr.statement().scope() == self._proxied:
                    if attr.args.args and attr.args.args[0].name == 'self':
                        yield BoundMethod(attr, self)
                        continue
                yield attr
            else:
                yield attr

    def infer_call_result(self, caller, context=None):
        """infer what a class instance is returning when called"""
        inferred = False
        for node in self._proxied.igetattr('__call__', context):
            if node is util.YES or not node.callable():
                continue
            for res in node.infer_call_result(caller, context):
                inferred = True
                yield res
        if not inferred:
            raise exceptions.InferenceError()

    def __repr__(self):
        return '<Instance of %s.%s at 0x%s>' % (self._proxied.root().name,
                                                self._proxied.name,
                                                id(self))
    def __str__(self):
        return 'Instance of %s.%s' % (self._proxied.root().name,
                                      self._proxied.name)

    def callable(self):
        try:
            self._proxied.getattr('__call__')
            return True
        except exceptions.NotFoundError:
            return False

    def pytype(self):
        return self._proxied.qname()

    def display_type(self):
        return 'Instance of'


    # TODO(cpopa): this is set in inference.py
    # The circular dependency hell goes deeper and deeper.
    # pylint: disable=unused-argument
    def getitem(self, index, context=None):
        pass

class UnboundMethod(Proxy):
    """a special node representing a method not bound to an instance"""
    def __repr__(self):
        frame = self._proxied.parent.frame()
        return '<%s %s of %s at 0x%s' % (self.__class__.__name__,
                                         self._proxied.name,
                                         frame.qname(), id(self))

    def is_bound(self):
        return False

    def getattr(self, name, context=None):
        if name == 'im_func':
            return [self._proxied]
        return self._proxied.getattr(name, context)

    def igetattr(self, name, context=None):
        if name == 'im_func':
            return iter((self._proxied,))
        return self._proxied.igetattr(name, context)

    def infer_call_result(self, caller, context):
        # If we're unbound method __new__ of builtin object, the result is an
        # instance of the class given as first argument.
        if (self._proxied.name == '__new__' and
                self._proxied.parent.frame().qname() == '%s.object' % BUILTINS):
            infer = caller.args[0].infer() if caller.args else []
            return ((x is util.YES and x or Instance(x)) for x in infer)
        return self._proxied.infer_call_result(caller, context)


class BoundMethod(UnboundMethod):
    """a special node representing a method bound to an instance"""
    def __init__(self, proxy, bound):
        UnboundMethod.__init__(self, proxy)
        self.bound = bound

    def is_bound(self):
        return True

    def infer_call_result(self, caller, context=None):

        if context is None:
            context = contextmod.InferenceContext()
        context = context.clone()
        context.boundnode = self.bound
        return super(BoundMethod, self).infer_call_result(caller, context)


class Generator(Instance):
    """a special node representing a generator.

    Proxied class is set once for all in raw_building.
    """
    def callable(self):
        return False

    def pytype(self):
        return '%s.generator' % BUILTINS

    def display_type(self):
        return 'Generator'

    def __repr__(self):
        return '<Generator(%s) l.%s at 0x%s>' % (self._proxied.name, self.lineno, id(self))

    def __str__(self):
        return 'Generator(%s)' % (self._proxied.name)


# decorators ##################################################################

def path_wrapper(func):
    """return the given infer function wrapped to handle the path"""
    @functools.wraps(func)
    def wrapped(node, context=None, _func=func, **kwargs):
        """wrapper function handling context"""
        if context is None:
            context = contextmod.InferenceContext()
        context.push(node)
        yielded = set()
        for res in _func(node, context, **kwargs):
            # unproxy only true instance, not const, tuple, dict...
            if res.__class__ is Instance:
                ares = res._proxied
            else:
                ares = res
            if ares not in yielded:
                yield res
                yielded.add(ares)
    return wrapped

@wrapt.decorator
def yes_if_nothing_inferred(func, instance, args, kwargs):
    inferred = False
    for node in func(*args, **kwargs):
        inferred = True
        yield node
    if not inferred:
        yield util.YES

@wrapt.decorator
def raise_if_nothing_inferred(func, instance, args, kwargs):
    inferred = False
    for node in func(*args, **kwargs):
        inferred = True
        yield node
    if not inferred:
        raise exceptions.InferenceError()


# Node  ######################################################################

class NodeNG(object):
    """Base Class for all Astroid node classes.

    It represents a node of the new abstract syntax tree.
    """
    is_statement = False
    optional_assign = False # True for For (and for Comprehension if py <3.0)
    is_function = False # True for FunctionDef nodes
    # attributes below are set by the builder module or by raw factories
    lineno = None
    fromlineno = None
    tolineno = None
    col_offset = None
    # parent node in the tree
    parent = None
    # attributes containing child node(s) redefined in most concrete classes:
    _astroid_fields = ()
    # instance specific inference function infer(node, context)
    _explicit_inference = None

    def infer(self, context=None, **kwargs):
        """main interface to the interface system, return a generator on infered
        values.

        If the instance has some explicit inference function set, it will be
        called instead of the default interface.
        """
        if self._explicit_inference is not None:
            # explicit_inference is not bound, give it self explicitly
            try:
                return self._explicit_inference(self, context, **kwargs)
            except exceptions.UseInferenceDefault:
                pass

        if not context:
            return self._infer(context, **kwargs)

        key = (self, context.lookupname,
               context.callcontext, context.boundnode)
        if key in context.inferred:
            return iter(context.inferred[key])

        return context.cache_generator(key, self._infer(context, **kwargs))

    def _repr_name(self):
        """return self.name or self.attrname or '' for nice representation"""
        return getattr(self, 'name', getattr(self, 'attrname', ''))

    def __str__(self):
        return '%s(%s)' % (self.__class__.__name__, self._repr_name())

    def __repr__(self):
        return '<%s(%s) l.%s [%s] at 0x%x>' % (self.__class__.__name__,
                                               self._repr_name(),
                                               self.fromlineno,
                                               self.root().name,
                                               id(self))


    def accept(self, visitor):
        func = getattr(visitor, "visit_" + self.__class__.__name__.lower())
        return func(self)

    def get_children(self):
        for field in self._astroid_fields:
            attr = getattr(self, field)
            if attr is None:
                continue
            if isinstance(attr, (list, tuple)):
                for elt in attr:
                    yield elt
            else:
                yield attr

    def last_child(self):
        """an optimized version of list(get_children())[-1]"""
        for field in self._astroid_fields[::-1]:
            attr = getattr(self, field)
            if not attr: # None or empty listy / tuple
                continue
            if isinstance(attr, (list, tuple)):
                return attr[-1]
            else:
                return attr
        return None

    def parent_of(self, node):
        """return true if i'm a parent of the given node"""
        parent = node.parent
        while parent is not None:
            if self is parent:
                return True
            parent = parent.parent
        return False

    def statement(self):
        """return the first parent node marked as statement node"""
        if self.is_statement:
            return self
        return self.parent.statement()

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

        """
        return self.parent.frame()

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

        """
        return self.parent.scope()

    def root(self):
        """return the root node of the tree, (i.e. a Module)"""
        if self.parent:
            return self.parent.root()
        return self

    def child_sequence(self, child):
        """search for the right sequence where the child lies in"""
        for field in self._astroid_fields:
            node_or_sequence = getattr(self, field)
            if node_or_sequence is child:
                return [node_or_sequence]
            # /!\ compiler.ast Nodes have an __iter__ walking over child nodes
            if (isinstance(node_or_sequence, (tuple, list))
                    and child in node_or_sequence):
                return node_or_sequence

        msg = 'Could not find %s in %s\'s children'
        raise exceptions.AstroidError(msg % (repr(child), repr(self)))

    def locate_child(self, child):
        """return a 2-uple (child attribute name, sequence or node)"""
        for field in self._astroid_fields:
            node_or_sequence = getattr(self, field)
            # /!\ compiler.ast Nodes have an __iter__ walking over child nodes
            if child is node_or_sequence:
                return field, child
            if isinstance(node_or_sequence, (tuple, list)) and child in node_or_sequence:
                return field, node_or_sequence
        msg = 'Could not find %s in %s\'s children'
        raise exceptions.AstroidError(msg % (repr(child), repr(self)))
    # FIXME : should we merge child_sequence and locate_child ? locate_child
    # is only used in are_exclusive, child_sequence one time in pylint.

    def next_sibling(self):
        """return the next sibling statement"""
        return self.parent.next_sibling()

    def previous_sibling(self):
        """return the previous sibling statement"""
        return self.parent.previous_sibling()

    def nearest(self, nodes):
        """return the node which is the nearest before this one in the
        given list of nodes
        """
        myroot = self.root()
        mylineno = self.fromlineno
        nearest = None, 0
        for node in nodes:
            assert node.root() is myroot, \
                   'nodes %s and %s are not from the same module' % (self, node)
            lineno = node.fromlineno
            if node.fromlineno > mylineno:
                break
            if lineno > nearest[1]:
                nearest = node, lineno
        # FIXME: raise an exception if nearest is None ?
        return nearest[0]

    # these are lazy because they're relatively expensive to compute for every
    # single node, and they rarely get looked at

    @decoratorsmod.cachedproperty
    def fromlineno(self):
        if self.lineno is None:
            return self._fixed_source_line()
        else:
            return self.lineno

    @decoratorsmod.cachedproperty
    def tolineno(self):
        if not self._astroid_fields:
            # can't have children
            lastchild = None
        else:
            lastchild = self.last_child()
        if lastchild is None:
            return self.fromlineno
        else:
            return lastchild.tolineno

        # TODO / FIXME:
        assert self.fromlineno is not None, self
        assert self.tolineno is not None, self

    def _fixed_source_line(self):
        """return the line number where the given node appears

        we need this method since not all nodes have the lineno attribute
        correctly set...
        """
        line = self.lineno
        _node = self
        try:
            while line is None:
                _node = next(_node.get_children())
                line = _node.lineno
        except StopIteration:
            _node = self.parent
            while _node and line is None:
                line = _node.lineno
                _node = _node.parent
        return line

    def block_range(self, lineno):
        """handle block line numbers range for non block opening statements
        """
        return lineno, self.tolineno

    def set_local(self, name, stmt):
        """delegate to a scoped parent handling a locals dictionary"""
        self.parent.set_local(name, stmt)

    def nodes_of_class(self, klass, skip_klass=None):
        """return an iterator on nodes which are instance of the given class(es)

        klass may be a class object or a tuple of class objects
        """
        if isinstance(self, klass):
            yield self
        for child_node in self.get_children():
            if skip_klass is not None and isinstance(child_node, skip_klass):
                continue
            for matching in child_node.nodes_of_class(klass, skip_klass):
                yield matching

    def _infer_name(self, frame, name):
        # overridden for ImportFrom, Import, Global, TryExcept and Arguments
        return None

    def _infer(self, context=None):
        """we don't know how to resolve a statement by default"""
        # this method is overridden by most concrete classes
        raise exceptions.InferenceError(self.__class__.__name__)

    def inferred(self):
        '''return list of inferred values for a more simple inference usage'''
        return list(self.infer())

    def infered(self):
        warnings.warn('%s.infered() is deprecated and slated for removal '
                      'in astroid 2.0, use %s.inferred() instead.'
                      % (type(self).__name__, type(self).__name__),
                      PendingDeprecationWarning, stacklevel=2)
        return self.inferred()

    def instanciate_class(self):
        """instanciate a node if it is a ClassDef node, else return self"""
        return self

    def has_base(self, node):
        return False

    def callable(self):
        return False

    def eq(self, value):
        return False

    def as_string(self):
        from astroid.as_string import to_code
        return to_code(self)

    def repr_tree(self, ids=False):
        from astroid.as_string import dump
        return dump(self)


class Statement(NodeNG):
    """Statement node adding a few attributes"""
    is_statement = True

    def next_sibling(self):
        """return the next sibling statement"""
        stmts = self.parent.child_sequence(self)
        index = stmts.index(self)
        try:
            return stmts[index +1]
        except IndexError:
            pass

    def previous_sibling(self):
        """return the previous sibling statement"""
        stmts = self.parent.child_sequence(self)
        index = stmts.index(self)
        if index >= 1:
            return stmts[index -1]