# Copyright (c) 2006-2011, 2013-2014 LOGILAB S.A. (Paris, FRANCE) <contact@logilab.fr>

# Copyright (c) 2013-2014 Google, Inc.

# Copyright (c) 2014-2016 Claudiu Popa <pcmanticore@gmail.com>

# Copyright (c) 2015-2016 Cara Vinson <ceridwenv@gmail.com>

# Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html

# For details: https://github.com/PyCQA/astroid/blob/master/COPYING.LESSER

"""this module contains a set of functions to handle inference on astroid trees

"""

import functools

import itertools

import operator

from astroid import bases

from astroid import context as contextmod

from astroid import exceptions

from astroid import decorators

from astroid import helpers

from astroid import manager

from astroid import nodes

from astroid.interpreter import dunder_lookup

from astroid import protocols

from astroid import util

MANAGER = manager.AstroidManager()

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

def infer_end(self, context=None):

"""inference's end for node such as Module, ClassDef, FunctionDef,

Const...

"""

yield self

nodes.Module._infer = infer_end

nodes.ClassDef._infer = infer_end

nodes.FunctionDef._infer = infer_end

nodes.Lambda._infer = infer_end

nodes.Const._infer = infer_end

nodes.Slice._infer = infer_end

def infer_seq(self, context=None):

if not any(isinstance(e, nodes.Starred) for e in self.elts):

yield self

else:

values = _infer_seq(self, context)

new_seq = type(self)(self.lineno, self.col_offset, self.parent)

new_seq.postinit(values)

yield new_seq

def _infer_seq(node, context=None):

"""Infer all values based on _BaseContainer.elts"""

values = []

for elt in node.elts:

if isinstance(elt, nodes.Starred):

starred = helpers.safe_infer(elt.value, context)

if starred in (None, util.Uninferable):

raise exceptions.InferenceError(node=node,

context=context)

if not hasattr(starred, 'elts'):

raise exceptions.InferenceError(node=node,

context=context)

values.extend(_infer_seq(starred))

else:

values.append(elt)

return values

nodes.List._infer = infer_seq

nodes.Tuple._infer = infer_seq

nodes.Set._infer = infer_seq

def infer_map(self, context=None):

if not any(isinstance(k, nodes.DictUnpack) for k, _ in self.items):

yield self

else:

items = _infer_map(self, context)

new_seq = type(self)(self.lineno, self.col_offset, self.parent)

new_seq.postinit(list(items.items()))

yield new_seq

def _infer_map(node, context):

"""Infer all values based on Dict.items"""

values = {}

for name, value in node.items:

if isinstance(name, nodes.DictUnpack):

double_starred = helpers.safe_infer(value, context)

if double_starred in (None, util.Uninferable):

raise exceptions.InferenceError

if not isinstance(double_starred, nodes.Dict):

raise exceptions.InferenceError(node=node,

context=context)

values.update(_infer_map(double_starred, context))

else:

key = helpers.safe_infer(name, context=context)

value = helpers.safe_infer(value, context=context)

if key is None or value is None:

raise exceptions.InferenceError(node=node,

context=context)

values[key] = value

return values

nodes.Dict._infer = infer_map

def _higher_function_scope(node):

""" Search for the first function which encloses the given

scope. This can be used for looking up in that function's

scope, in case looking up in a lower scope for a particular

name fails.

:param node: A scope node.

:returns:

``None``, if no parent function scope was found,

otherwise an instance of :class:`astroid.scoped_nodes.Function`,

which encloses the given node.

"""

current = node

while current.parent and not isinstance(current.parent, nodes.FunctionDef):

current = current.parent

if current and current.parent:

return current.parent

def infer_name(self, context=None):

"""infer a Name: use name lookup rules"""

frame, stmts = self.lookup(self.name)

if not stmts:

# Try to see if the name is enclosed in a nested function

# and use the higher (first function) scope for searching.

# TODO: should this be promoted to other nodes as well?

parent_function = _higher_function_scope(self.scope())

if parent_function:

_, stmts = parent_function.lookup(self.name)

if not stmts:

raise exceptions.NameInferenceError(name=self.name,

scope=self.scope(),

context=context)

context = context.clone()

context.lookupname = self.name

return bases._infer_stmts(stmts, context, frame)

nodes.Name._infer = decorators.path_wrapper(infer_name)

nodes.AssignName.infer_lhs = infer_name # won't work with a path wrapper

@decorators.raise_if_nothing_inferred

@decorators.path_wrapper

def infer_call(self, context=None):

"""infer a Call node by trying to guess what the function returns"""

callcontext = context.clone()

callcontext.callcontext = contextmod.CallContext(args=self.args,

keywords=self.keywords)

callcontext.boundnode = None

for callee in self.func.infer(context):

if callee is util.Uninferable:

yield callee

continue

try:

if hasattr(callee, 'infer_call_result'):

for inferred in callee.infer_call_result(self, callcontext):

yield inferred

except exceptions.InferenceError:

## XXX log error ?

continue

# Explicit StopIteration to return error information, see comment

# in raise_if_nothing_inferred.

raise StopIteration(dict(node=self, context=context))

nodes.Call._infer = infer_call

@decorators.path_wrapper

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 exceptions.InferenceError(node=self, context=context)

try:

if asname:

yield self.do_import_module(self.real_name(name))

else:

yield self.do_import_module(name)

except exceptions.AstroidBuildingError as exc:

util.reraise(exceptions.InferenceError(node=self, error=exc,

context=context))

nodes.Import._infer = infer_import

def infer_name_module(self, name):

context = contextmod.InferenceContext()

context.lookupname = name

return self.infer(context, asname=False)

nodes.Import.infer_name_module = infer_name_module

@decorators.path_wrapper

def infer_import_from(self, context=None, asname=True):

"""infer a ImportFrom node: return the imported module/object"""

name = context.lookupname

if name is None:

raise exceptions.InferenceError(node=self, context=context)

if asname:

name = self.real_name(name)

try:

module = self.do_import_module()

except exceptions.AstroidBuildingError as exc:

util.reraise(exceptions.InferenceError(node=self, error=exc,

context=context))

try:

context = contextmod.copy_context(context)

context.lookupname = name

stmts = module.getattr(name, ignore_locals=module is self.root())

return bases._infer_stmts(stmts, context)

except exceptions.AttributeInferenceError as error:

util.reraise(exceptions.InferenceError(

error.message, target=self, attribute=name, context=context))

nodes.ImportFrom._infer = infer_import_from

@decorators.raise_if_nothing_inferred

def infer_attribute(self, context=None):

"""infer an Attribute node by using getattr on the associated object"""

for owner in self.expr.infer(context):

if owner is util.Uninferable:

yield owner

continue

if context and context.boundnode:

# This handles the situation where the attribute is accessed through a subclass

# of a base class and the attribute is defined at the base class's level,

# by taking in consideration a redefinition in the subclass.

if (isinstance(owner, bases.Instance)

and isinstance(context.boundnode, bases.Instance)):

try:

if helpers.is_subtype(helpers.object_type(context.boundnode),

helpers.object_type(owner)):

owner = context.boundnode

except exceptions._NonDeducibleTypeHierarchy:

# Can't determine anything useful.

pass

try:

context.boundnode = owner

for obj in owner.igetattr(self.attrname, context):

yield obj

context.boundnode = None

except (exceptions.AttributeInferenceError, exceptions.InferenceError):

context.boundnode = None

except AttributeError:

# XXX method / function

context.boundnode = None

# Explicit StopIteration to return error information, see comment

# in raise_if_nothing_inferred.

raise StopIteration(dict(node=self, context=context))

nodes.Attribute._infer = decorators.path_wrapper(infer_attribute)

nodes.AssignAttr.infer_lhs = infer_attribute # # won't work with a path wrapper

@decorators.path_wrapper

def infer_global(self, context=None):

if context.lookupname is None:

raise exceptions.InferenceError(node=self, context=context)

try:

return bases._infer_stmts(self.root().getattr(context.lookupname),

context)

except exceptions.AttributeInferenceError as error:

util.reraise(exceptions.InferenceError(

error.message, target=self, attribute=context.lookupname,

context=context))

nodes.Global._infer = infer_global

_SUBSCRIPT_SENTINEL = object()

@decorators.raise_if_nothing_inferred

def infer_subscript(self, context=None):

"""Inference for subscripts

We're understanding if the index is a Const

or a slice, passing the result of inference

to the value's `getitem` method, which should

handle each supported index type accordingly.

"""

value = next(self.value.infer(context))

if value is util.Uninferable:

yield util.Uninferable

return

index = next(self.slice.infer(context))

if index is util.Uninferable:

yield util.Uninferable

return

# Try to deduce the index value.

index_value = _SUBSCRIPT_SENTINEL

if value.__class__ == bases.Instance:

index_value = index

else:

if index.__class__ == bases.Instance:

instance_as_index = helpers.class_instance_as_index(index)

if instance_as_index:

index_value = instance_as_index

else:

index_value = index

if index_value is _SUBSCRIPT_SENTINEL:

raise exceptions.InferenceError(node=self, context=context)

try:

assigned = value.getitem(index_value, context)

except (exceptions.AstroidTypeError,

exceptions.AstroidIndexError,

exceptions.AttributeInferenceError,

AttributeError) as exc:

util.reraise(exceptions.InferenceError(node=self, error=exc,

context=context))

# Prevent inferring if the inferred subscript

# is the same as the original subscripted object.

if self is assigned or assigned is util.Uninferable:

yield util.Uninferable

return

for inferred in assigned.infer(context):

yield inferred

# Explicit StopIteration to return error information, see comment

# in raise_if_nothing_inferred.

raise StopIteration(dict(node=self, context=context))

nodes.Subscript._infer = decorators.path_wrapper(infer_subscript)

nodes.Subscript.infer_lhs = infer_subscript

@decorators.raise_if_nothing_inferred

@decorators.path_wrapper

def _infer_boolop(self, context=None):

"""Infer a boolean operation (and / or / not).

The function will calculate the boolean operation

for all pairs generated through inference for each component

node.

"""

values = self.values

if self.op == 'or':

predicate = operator.truth

else:

predicate = operator.not_

try:

values = [value.infer(context=context) for value in values]

except exceptions.InferenceError:

yield util.Uninferable

return

for pair in itertools.product(*values):

if any(item is util.Uninferable for item in pair):

# Can't infer the final result, just yield Uninferable.

yield util.Uninferable

continue

bool_values = [item.bool_value() for item in pair]

if any(item is util.Uninferable for item in bool_values):

# Can't infer the final result, just yield Uninferable.

yield util.Uninferable

continue

# Since the boolean operations are short circuited operations,

# this code yields the first value for which the predicate is True

# and if no value respected the predicate, then the last value will

# be returned (or Uninferable if there was no last value).

# This is conforming to the semantics of `and` and `or`:

# 1 and 0 -> 1

# 0 and 1 -> 0

# 1 or 0 -> 1

# 0 or 1 -> 1

value = util.Uninferable

for value, bool_value in zip(pair, bool_values):

if predicate(bool_value):

yield value

break

else:

yield value

# Explicit StopIteration to return error information, see comment

# in raise_if_nothing_inferred.

raise StopIteration(dict(node=self, context=context))

nodes.BoolOp._infer = _infer_boolop

# UnaryOp, BinOp and AugAssign inferences

def _filter_operation_errors(self, infer_callable, context, error):

for result in infer_callable(self, context):

if isinstance(result, error):

# For the sake of .infer(), we don't care about operation

# errors, which is the job of pylint. So return something

# which shows that we can't infer the result.

yield util.Uninferable

else:

yield result

def _infer_unaryop(self, context=None):

"""Infer what an UnaryOp should return when evaluated."""

for operand in self.operand.infer(context):

try:

yield operand.infer_unary_op(self.op)

except TypeError as exc:

# The operand doesn't support this operation.

yield util.BadUnaryOperationMessage(operand, self.op, exc)

except AttributeError as exc:

meth = protocols.UNARY_OP_METHOD[self.op]

if meth is None:

# `not node`. Determine node's boolean

# value and negate its result, unless it is

# Uninferable, which will be returned as is.

bool_value = operand.bool_value()

if bool_value is not util.Uninferable:

yield nodes.const_factory(not bool_value)

else:

yield util.Uninferable

else:

if not isinstance(operand, (bases.Instance, nodes.ClassDef)):

# The operation was used on something which

# doesn't support it.

yield util.BadUnaryOperationMessage(operand, self.op, exc)

continue

try:

try:

methods = dunder_lookup.lookup(operand, meth)

except exceptions.AttributeInferenceError:

yield util.BadUnaryOperationMessage(operand, self.op, exc)

continue

meth = methods[0]

inferred = next(meth.infer(context=context))

if inferred is util.Uninferable or not inferred.callable():

continue

context = contextmod.copy_context(context)

context.callcontext = contextmod.CallContext(args=[operand])

call_results = inferred.infer_call_result(self, context=context)

result = next(call_results, None)

if result is None:

# Failed to infer, return the same type.

yield operand

else:

yield result

except exceptions.AttributeInferenceError as exc:

# The unary operation special method was not found.

yield util.BadUnaryOperationMessage(operand, self.op, exc)

except exceptions.InferenceError:

yield util.Uninferable

@decorators.raise_if_nothing_inferred

@decorators.path_wrapper

def infer_unaryop(self, context=None):

"""Infer what an UnaryOp should return when evaluated."""

for inferred in _filter_operation_errors(self, _infer_unaryop, context,

util.BadUnaryOperationMessage):

yield inferred

# Explicit StopIteration to return error information, see comment

# in raise_if_nothing_inferred.

raise StopIteration(dict(node=self, context=context))

nodes.UnaryOp._infer_unaryop = _infer_unaryop

nodes.UnaryOp._infer = infer_unaryop

def _is_not_implemented(const):

"""Check if the given const node is NotImplemented."""

return isinstance(const, nodes.Const) and const.value is NotImplemented

def _invoke_binop_inference(instance, opnode, op, other, context, method_name):

"""Invoke binary operation inference on the given instance."""

methods = dunder_lookup.lookup(instance, method_name)

method = methods[0]

inferred = next(method.infer(context=context))

return instance.infer_binary_op(opnode, op, other, context, inferred)

def _aug_op(instance, opnode, op, other, context, reverse=False):

"""Get an inference callable for an augmented binary operation."""

method_name = protocols.AUGMENTED_OP_METHOD[op]

return functools.partial(_invoke_binop_inference,

instance=instance,

op=op, opnode=opnode, other=other,

context=context,

method_name=method_name)

def _bin_op(instance, opnode, op, other, context, reverse=False):

"""Get an inference callable for a normal binary operation.

If *reverse* is True, then the reflected method will be used instead.

"""

if reverse:

method_name = protocols.REFLECTED_BIN_OP_METHOD[op]

else:

method_name = protocols.BIN_OP_METHOD[op]

return functools.partial(_invoke_binop_inference,

instance=instance,

op=op, opnode=opnode, other=other,

context=context,

method_name=method_name)

def _get_binop_contexts(context, left, right):

"""Get contexts for binary operations.

This will return two inferrence contexts, the first one

for x.__op__(y), the other one for y.__rop__(x), where

only the arguments are inversed.

"""

# The order is important, since the first one should be

# left.__op__(right).

for arg in (right, left):

new_context = context.clone()

new_context.callcontext = contextmod.CallContext(args=[arg])

new_context.boundnode = None

yield new_context

def _same_type(type1, type2):

"""Check if type1 is the same as type2."""

return type1.qname() == type2.qname()

def _get_binop_flow(left, left_type, binary_opnode, right, right_type,

context, reverse_context):

"""Get the flow for binary operations.

The rules are a bit messy:

* if left and right have the same type, then only one

method will be called, left.__op__(right)

* if left and right are unrelated typewise, then first

left.__op__(right) is tried and if this does not exist

or returns NotImplemented, then right.__rop__(left) is tried.

* if left is a subtype of right, then only left.__op__(right)

is tried.

* if left is a supertype of right, then right.__rop__(left)

is first tried and then left.__op__(right)

"""

op = binary_opnode.op

if _same_type(left_type, right_type):

methods = [_bin_op(left, binary_opnode, op, right, context)]

elif helpers.is_subtype(left_type, right_type):

methods = [_bin_op(left, binary_opnode, op, right, context)]

elif helpers.is_supertype(left_type, right_type):

methods = [_bin_op(right, binary_opnode, op, left, reverse_context, reverse=True),

_bin_op(left, binary_opnode, op, right, context)]

else:

methods = [_bin_op(left, binary_opnode, op, right, context),

_bin_op(right, binary_opnode, op, left, reverse_context, reverse=True)]

return methods

def _get_aug_flow(left, left_type, aug_opnode, right, right_type,

context, reverse_context):

"""Get the flow for augmented binary operations.

The rules are a bit messy:

* if left and right have the same type, then left.__augop__(right)

is first tried and then left.__op__(right).

* if left and right are unrelated typewise, then

left.__augop__(right) is tried, then left.__op__(right)

is tried and then right.__rop__(left) is tried.

* if left is a subtype of right, then left.__augop__(right)

is tried and then left.__op__(right).

* if left is a supertype of right, then left.__augop__(right)

is tried, then right.__rop__(left) and then

left.__op__(right)

"""

bin_op = aug_opnode.op.strip("=")

aug_op = aug_opnode.op

if _same_type(left_type, right_type):

methods = [_aug_op(left, aug_opnode, aug_op, right, context),

_bin_op(left, aug_opnode, bin_op, right, context)]

elif helpers.is_subtype(left_type, right_type):

methods = [_aug_op(left, aug_opnode, aug_op, right, context),

_bin_op(left, aug_opnode, bin_op, right, context)]

elif helpers.is_supertype(left_type, right_type):

methods = [_aug_op(left, aug_opnode, aug_op, right, context),

_bin_op(right, aug_opnode, bin_op, left, reverse_context, reverse=True),

_bin_op(left, aug_opnode, bin_op, right, context)]

else:

methods = [_aug_op(left, aug_opnode, aug_op, right, context),

_bin_op(left, aug_opnode, bin_op, right, context),

_bin_op(right, aug_opnode, bin_op, left, reverse_context, reverse=True)]

return methods

def _infer_binary_operation(left, right, binary_opnode, context, flow_factory):

"""Infer a binary operation between a left operand and a right operand

This is used by both normal binary operations and augmented binary

operations, the only difference is the flow factory used.

"""

context, reverse_context = _get_binop_contexts(context, left, right)

left_type = helpers.object_type(left)

right_type = helpers.object_type(right)

methods = flow_factory(left, left_type, binary_opnode, right, right_type,

context, reverse_context)

for method in methods:

try:

results = list(method())

except AttributeError:

continue

except exceptions.AttributeInferenceError:

continue

except exceptions.InferenceError:

yield util.Uninferable

return

else:

if any(result is util.Uninferable for result in results):

yield util.Uninferable

return

# TODO(cpopa): since the inference engine might return

# more values than are actually possible, we decide

# to return util.Uninferable if we have union types.

if all(map(_is_not_implemented, results)):

continue

not_implemented = sum(1 for result in results

if _is_not_implemented(result))

if not_implemented and not_implemented != len(results):

# Can't decide yet what this is, not yet though.

yield util.Uninferable

return

for result in results:

yield result

return

# TODO(cpopa): yield a BadBinaryOperationMessage here,

# since the operation is not supported

yield util.BadBinaryOperationMessage(left_type, binary_opnode.op, right_type)

def _infer_binop(self, context):

"""Binary operation inferrence logic."""

if context is None:

context = contextmod.InferenceContext()

left = self.left

right = self.right

# we use two separate contexts for evaluating lhs and rhs because

# 1. evaluating lhs may leave some undesired entries in context.path

# which may not let us infer right value of rhs

lhs_context = context.clone()

rhs_context = context.clone()

for lhs in left.infer(context=lhs_context):

if lhs is util.Uninferable:

# Don't know how to process this.

yield util.Uninferable

return

for rhs in right.infer(context=rhs_context):

if rhs is util.Uninferable:

# Don't know how to process this.

yield util.Uninferable

return

try:

for result in _infer_binary_operation(lhs, rhs, self,

context, _get_binop_flow):

yield result

except exceptions._NonDeducibleTypeHierarchy:

yield util.Uninferable

@decorators.yes_if_nothing_inferred

@decorators.path_wrapper

def infer_binop(self, context=None):

return _filter_operation_errors(self, _infer_binop, context,

util.BadBinaryOperationMessage)

nodes.BinOp._infer_binop = _infer_binop

nodes.BinOp._infer = infer_binop

def _infer_augassign(self, context=None):

"""Inference logic for augmented binary operations."""

if context is None:

context = contextmod.InferenceContext()

for lhs in self.target.infer_lhs(context=context):

if lhs is util.Uninferable:

# Don't know how to process this.

yield util.Uninferable

return

# TODO(cpopa): if we have A() * A(), trying to infer

# the rhs with the same context will result in an

# inference error, so we create another context for it.

# This is a bug which should be fixed in InferenceContext at some point.

rhs_context = context.clone()

rhs_context.path = set()

for rhs in self.value.infer(context=rhs_context):

if rhs is util.Uninferable:

# Don't know how to process this.

yield util.Uninferable

return

try:

results = _infer_binary_operation(lhs, rhs, self, context, _get_aug_flow)

except exceptions._NonDeducibleTypeHierarchy:

yield util.Uninferable

else:

for result in results:

yield result

@decorators.path_wrapper

def infer_augassign(self, context=None):

return _filter_operation_errors(self, _infer_augassign, context,

util.BadBinaryOperationMessage)

nodes.AugAssign._infer_augassign = _infer_augassign

nodes.AugAssign._infer = infer_augassign

# End of binary operation inference.

def infer_arguments(self, context=None):

name = context.lookupname

if name is None:

raise exceptions.InferenceError(node=self, context=context)

return protocols._arguments_infer_argname(self, name, context)

nodes.Arguments._infer = infer_arguments

@decorators.path_wrapper

def infer_assign(self, context=None):

"""infer a AssignName/AssignAttr: 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 bases._infer_stmts(stmts, context)

nodes.AssignName._infer = infer_assign

nodes.AssignAttr._infer = infer_assign

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

@decorators.path_wrapper

def infer_empty_node(self, context=None):

if not self.has_underlying_object():

yield util.Uninferable

else:

try:

for inferred in MANAGER.infer_ast_from_something(self.object,

context=context):

yield inferred

except exceptions.AstroidError:

yield util.Uninferable

nodes.EmptyNode._infer = infer_empty_node

def infer_index(self, context=None):

return self.value.infer(context)

nodes.Index._infer = infer_index

# TODO: move directly into bases.Instance when the dependency hell

# will be solved.

def instance_getitem(self, index, context=None):

# Rewrap index to Const for this case

if context:

new_context = context.clone()

else:

context = new_context = contextmod.InferenceContext()

# Create a new callcontext for providing index as an argument.

new_context.callcontext = contextmod.CallContext(args=[index])

new_context.boundnode = self

method = next(self.igetattr('__getitem__', context=context))

if not isinstance(method, bases.BoundMethod):

raise exceptions.InferenceError(

'Could not find __getitem__ for {node!r}.',

node=self, context=context)

try:

return next(method.infer_call_result(self, new_context))

except StopIteration:

util.reraise(exceptions.InferenceError(

message='Inference for {node!r}[{index!s}] failed.',

node=self, index=index, context=context))

bases.Instance.getitem = instance_getitem