/tools/logilab/astng/inference.py

# copyright 2003-2011 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
# copyright 2003-2010 Sylvain Thenault, all rights reserved.
# contact mailto:thenault@gmail.com
#
# This file is part of logilab-astng.
#
# logilab-astng 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.
#
# logilab-astng 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 logilab-astng. If not, see <http://www.gnu.org/licenses/>.
"""this module contains a set of functions to handle inference on astng trees
"""

__doctype__ = "restructuredtext en"

from itertools import chain
import sys

from logilab.astng import nodes

from logilab.astng.manager import ASTNGManager
from logilab.astng.exceptions import (ASTNGBuildingException, ASTNGError,
    InferenceError, NoDefault, NotFoundError, UnresolvableName)
from logilab.astng.bases import YES, Instance, InferenceContext, Generator, \
     _infer_stmts, copy_context, path_wrapper, raise_if_nothing_infered
from logilab.astng.protocols import _arguments_infer_argname

MANAGER = ASTNGManager()


class CallContext:
    """when inferring a function call, this class is used to remember values
    given as argument
    """
    def __init__(self, args, starargs, dstarargs):
        self.args = []
        self.nargs = {}
        for arg in args:
            if isinstance(arg, nodes.Keyword):
                self.nargs[arg.arg] = arg.value
            else:
                self.args.append(arg)
        self.starargs = starargs
        self.dstarargs = dstarargs

    def infer_argument(self, funcnode, name, context):
        """infer a function argument value according to the call context"""
        # 1. search in named keywords
        try:
            return self.nargs[name].infer(context)
        except KeyError:
            # Function.args.args can be None in astng (means that we don't have
            # information on argnames)
            argindex = funcnode.args.find_argname(name)[0]
            if argindex is not None:
                # 2. first argument of instance/class method
                if argindex == 0 and funcnode.type in ('method', 'classmethod'):
                    if context.boundnode is not None:
                        boundnode = context.boundnode
                    else:
                        # XXX can do better ?
                        boundnode = funcnode.parent.frame()
                    if funcnode.type == 'method':
                        if not isinstance(boundnode, Instance):
                            boundnode = Instance(boundnode)
                        return iter((boundnode,))
                    if funcnode.type == 'classmethod':
                        return iter((boundnode,))
                # 2. search arg index
                try:
                    return self.args[argindex].infer(context)
                except IndexError:
                    pass
                # 3. search in *args (.starargs)
                if self.starargs is not None:
                    its = []
                    for infered in self.starargs.infer(context):
                        if infered is YES:
                            its.append((YES,))
                            continue
                        try:
                            its.append(infered.getitem(argindex, context).infer(context))
                        except (InferenceError, AttributeError):
                            its.append((YES,))
                        except (IndexError, TypeError):
                            continue
                    if its:
                        return chain(*its)
        # 4. XXX search in **kwargs (.dstarargs)
        if self.dstarargs is not None:
            its = []
            for infered in self.dstarargs.infer(context):
                if infered is YES:
                    its.append((YES,))
                    continue
                try:
                    its.append(infered.getitem(name, context).infer(context))
                except (InferenceError, AttributeError):
                    its.append((YES,))
                except (IndexError, TypeError):
                    continue
            if its:
                return chain(*its)
        # 5. */** argument, (Tuple or Dict)
        if name == funcnode.args.vararg:
            return iter((nodes.const_factory(())))
        if name == funcnode.args.kwarg:
            return iter((nodes.const_factory({})))
        # 6. return default value if any
        try:
            return funcnode.args.default_value(name).infer(context)
        except NoDefault:
            raise InferenceError(name)


# .infer method ###############################################################


def infer_end(self, context=None):
    """inference's end for node such as Module, Class, Function, Const...
    """
    yield self
nodes.Module.infer = infer_end
nodes.Class.infer = infer_end
nodes.Function.infer = infer_end
nodes.Lambda.infer = infer_end
nodes.Const.infer = infer_end
nodes.List.infer = infer_end
nodes.Tuple.infer = infer_end
nodes.Dict.infer = infer_end


def infer_name(self, context=None):
    """infer a Name: use name lookup rules"""
    frame, stmts = self.lookup(self.name)
    if not stmts:
        raise UnresolvableName(self.name)
    context = context.clone()
    context.lookupname = self.name
    return _infer_stmts(stmts, context, frame)
nodes.Name.infer = path_wrapper(infer_name)
nodes.AssName.infer_lhs = infer_name # won't work with a path wrapper


def infer_callfunc(self, context=None):
    """infer a CallFunc node by trying to guess what the function returns"""
    callcontext = context.clone()
    callcontext.callcontext = CallContext(self.args, self.starargs, self.kwargs)
    callcontext.boundnode = None
    for callee in self.func.infer(context):
        if callee is YES:
            yield callee
            continue
        try:
            if hasattr(callee, 'infer_call_result'):
                for infered in callee.infer_call_result(self, callcontext):
                    yield infered
        except InferenceError:
            ## XXX log error ?
            continue
nodes.CallFunc.infer = path_wrapper(raise_if_nothing_infered(infer_callfunc))


def infer_import(self, context=None, asname=True):
    """infer an Import node: return the imported module/object"""
    name = context.lookupname
    if name is None:
        raise InferenceError()
    if asname:
        yield self.do_import_module(self.real_name(name))
    else:
        yield self.do_import_module(name)
nodes.Import.infer = path_wrapper(infer_import)

def infer_name_module(self, name):
    context = InferenceContext()
    context.lookupname = name
    return self.infer(context, asname=False)
nodes.Import.infer_name_module = infer_name_module


def infer_from(self, context=None, asname=True):
    """infer a From nodes: return the imported module/object"""
    name = context.lookupname
    if name is None:
        raise InferenceError()
    if asname:
        name = self.real_name(name)
    module = self.do_import_module(self.modname)
    try:
        context = copy_context(context)
        context.lookupname = name
        return _infer_stmts(module.getattr(name, ignore_locals=module is self.root()), context)
    except NotFoundError:
        raise InferenceError(name)
nodes.From.infer = path_wrapper(infer_from)


def infer_getattr(self, context=None):
    """infer a Getattr node by using getattr on the associated object"""
    #context = context.clone()
    for owner in self.expr.infer(context):
        if owner is YES:
            yield owner
            continue
        try:
            context.boundnode = owner
            for obj in owner.igetattr(self.attrname, context):
                yield obj
            context.boundnode = None
        except (NotFoundError, InferenceError):
            context.boundnode = None
        except AttributeError:
            # XXX method / function
            context.boundnode = None
nodes.Getattr.infer = path_wrapper(raise_if_nothing_infered(infer_getattr))
nodes.AssAttr.infer_lhs = raise_if_nothing_infered(infer_getattr) # # won't work with a path wrapper


def infer_global(self, context=None):
    if context.lookupname is None:
        raise InferenceError()
    try:
        return _infer_stmts(self.root().getattr(context.lookupname), context)
    except NotFoundError:
        raise InferenceError()
nodes.Global.infer = path_wrapper(infer_global)


def infer_subscript(self, context=None):
    """infer simple subscription such as [1,2,3][0] or (1,2,3)[-1]"""
    if isinstance(self.slice, nodes.Index):
        index = self.slice.value.infer(context).next()
        if index is YES:
            yield YES
            return
        try:
            # suppose it's a Tuple/List node (attribute error else)
            assigned = self.value.getitem(index.value, context)
        except AttributeError:
            raise InferenceError()
        except (IndexError, TypeError):
            yield YES
            return
        for infered in assigned.infer(context):
            yield infered
    else:
        raise InferenceError()
nodes.Subscript.infer = path_wrapper(infer_subscript)
nodes.Subscript.infer_lhs = raise_if_nothing_infered(infer_subscript)


UNARY_OP_METHOD = {'+': '__pos__',
                   '-': '__neg__',
                   '~': '__invert__',
                   'not': None, # XXX not '__nonzero__'
                  }

def infer_unaryop(self, context=None):
    for operand in self.operand.infer(context):
        try:
            yield operand.infer_unary_op(self.op)
        except TypeError:
            continue
        except AttributeError:
            meth = UNARY_OP_METHOD[self.op]
            if meth is None:
                yield YES
            else:
                try:
                    # XXX just suppose if the type implement meth, returned type
                    # will be the same
                    operand.getattr(meth)
                    yield operand
                except GeneratorExit:
                    raise
                except:
                    yield YES
nodes.UnaryOp.infer = path_wrapper(infer_unaryop)


BIN_OP_METHOD = {'+':  '__add__',
                 '-':  '__sub__',
                 '/':  '__div__',
                 '//': '__floordiv__',
                 '*':  '__mul__',
                 '**': '__power__',
                 '%':  '__mod__',
                 '&':  '__and__',
                 '|':  '__or__',
                 '^':  '__xor__',
                 '<<': '__lshift__',
                 '>>': '__rshift__',
                 }

def _infer_binop(operator, operand1, operand2, context, failures=None):
    if operand1 is YES:
        yield operand1
        return
    try:
        for valnode in operand1.infer_binary_op(operator, operand2, context):
            yield valnode
    except AttributeError:
        try:
            # XXX just suppose if the type implement meth, returned type
            # will be the same
            operand1.getattr(BIN_OP_METHOD[operator])
            yield operand1
        except:
            if failures is None:
                yield YES
            else:
                failures.append(operand1)

def infer_binop(self, context=None):
    failures = []
    for lhs in self.left.infer(context):
        for val in _infer_binop(self.op, lhs, self.right, context, failures):
            yield val
    for lhs in failures:
        for rhs in self.right.infer(context):
            for val in _infer_binop(self.op, rhs, lhs, context):
                yield val
nodes.BinOp.infer = path_wrapper(infer_binop)


def infer_arguments(self, context=None):
    name = context.lookupname
    if name is None:
        raise InferenceError()
    return _arguments_infer_argname(self, name, context)
nodes.Arguments.infer = infer_arguments


def infer_ass(self, context=None):
    """infer a AssName/AssAttr: need to inspect the RHS part of the
    assign node
    """
    stmt = self.statement()
    if isinstance(stmt, nodes.AugAssign):
        return stmt.infer(context)
    stmts = list(self.assigned_stmts(context=context))
    return _infer_stmts(stmts, context)
nodes.AssName.infer = path_wrapper(infer_ass)
nodes.AssAttr.infer = path_wrapper(infer_ass)

def infer_augassign(self, context=None):
    failures = []
    for lhs in self.target.infer_lhs(context):
        for val in _infer_binop(self.op, lhs, self.value, context, failures):
            yield val
    for lhs in failures:
        for rhs in self.value.infer(context):
            for val in _infer_binop(self.op, rhs, lhs, context):
                yield val
nodes.AugAssign.infer = path_wrapper(infer_augassign)


# no infer method on DelName and DelAttr (expected InferenceError)


def infer_empty_node(self, context=None):
    if not self.has_underlying_object():
        yield YES
    else:
        try:
            for infered in MANAGER.infer_astng_from_something(self.object,
                                                              context=context):
                yield infered
        except ASTNGError:
            yield YES
nodes.EmptyNode.infer = path_wrapper(infer_empty_node)