# -*- coding: utf-8 -*- # Copyright (c) 2006-2011, 2013-2014 LOGILAB S.A. (Paris, FRANCE) # Copyright (c) 2012 FELD Boris # Copyright (c) 2013-2014 Google, Inc. # Copyright (c) 2014-2018 Claudiu Popa # Copyright (c) 2014 Eevee (Alex Munroe) # Copyright (c) 2015-2016 Ceridwen # Copyright (c) 2015 Dmitry Pribysh # Copyright (c) 2016 Jakub Wilk # Copyright (c) 2017 Michał Masłowski # Copyright (c) 2017 Calen Pennington # Copyright (c) 2017 Łukasz Rogalski # Copyright (c) 2018 Bryce Guinta # Copyright (c) 2018 Nick Drozd # Copyright (c) 2018 Ashley Whetter # Copyright (c) 2018 HoverHell # 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_sequence_helper(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 not starred: raise exceptions.InferenceError(node=node, context=context) if not hasattr(starred, "elts"): raise exceptions.InferenceError(node=node, context=context) values.extend(_infer_sequence_helper(starred)) else: values.append(elt) return values @decorators.raise_if_nothing_inferred def infer_sequence(self, context=None): if not any(isinstance(e, nodes.Starred) for e in self.elts): yield self else: values = _infer_sequence_helper(self, context) new_seq = type(self)( lineno=self.lineno, col_offset=self.col_offset, parent=self.parent ) new_seq.postinit(values) yield new_seq nodes.List._infer = infer_sequence nodes.Tuple._infer = infer_sequence nodes.Set._infer = infer_sequence 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 _update_with_replacement(lhs_dict, rhs_dict): """Delete nodes that equate to duplicate keys Since an astroid node doesn't 'equal' another node with the same value, this function uses the as_string method to make sure duplicate keys don't get through Note that both the key and the value are astroid nodes Fixes issue with DictUnpack causing duplicte keys in inferred Dict items :param dict(nodes.NodeNG, nodes.NodeNG) lhs_dict: Dictionary to 'merge' nodes into :param dict(nodes.NodeNG, nodes.NodeNG) rhs_dict: Dictionary with nodes to pull from :return dict(nodes.NodeNG, nodes.NodeNG): merged dictionary of nodes """ combined_dict = itertools.chain(lhs_dict.items(), rhs_dict.items()) # Overwrite keys which have the same string values string_map = {key.as_string(): (key, value) for key, value in combined_dict} # Return to dictionary return dict(string_map.values()) 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 not double_starred: raise exceptions.InferenceError if not isinstance(double_starred, nodes.Dict): raise exceptions.InferenceError(node=node, context=context) unpack_items = _infer_map(double_starred, context) values = _update_with_replacement(values, unpack_items) else: key = helpers.safe_infer(name, context=context) value = helpers.safe_infer(value, context=context) if any(not elem for elem in (key, value)): raise exceptions.InferenceError(node=node, context=context) values = _update_with_replacement(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 return None 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. 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 = contextmod.copy_context(context) context.lookupname = self.name return bases._infer_stmts(stmts, context, frame) # pylint: disable=no-value-for-parameter nodes.Name._infer = decorators.raise_if_nothing_inferred( 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 = contextmod.copy_context(context) callcontext.callcontext = contextmod.CallContext( args=self.args, keywords=self.keywords ) callcontext.boundnode = None if context is not None: callcontext.extra_context = _populate_context_lookup(self, context.clone()) for callee in self.func.infer(context): if callee is util.Uninferable: yield callee continue try: if hasattr(callee, "infer_call_result"): yield from callee.infer_call_result(caller=self, context=callcontext) except exceptions.InferenceError: continue return dict(node=self, context=context) nodes.Call._infer = infer_call @decorators.raise_if_nothing_inferred @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: raise exceptions.InferenceError(node=self, context=context) from exc nodes.Import._infer = infer_import @decorators.raise_if_nothing_inferred @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: raise exceptions.InferenceError(node=self, context=context) from exc 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: raise exceptions.InferenceError( error.message, target=self, attribute=name, context=context ) from error nodes.ImportFrom._infer = infer_import_from 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 yield from owner.igetattr(self.attrname, context) context.boundnode = None except (exceptions.AttributeInferenceError, exceptions.InferenceError): context.boundnode = None except AttributeError: # XXX method / function context.boundnode = None return dict(node=self, context=context) nodes.Attribute._infer = decorators.raise_if_nothing_inferred( decorators.path_wrapper(infer_attribute) ) # won't work with a path wrapper nodes.AssignAttr.infer_lhs = decorators.raise_if_nothing_inferred(infer_attribute) @decorators.raise_if_nothing_inferred @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: raise exceptions.InferenceError( error.message, target=self, attribute=context.lookupname, context=context ) from error 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. """ found_one = False for value in self.value.infer(context): if value is util.Uninferable: yield util.Uninferable return None for index in self.slice.infer(context): if index is util.Uninferable: yield util.Uninferable return None # 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: raise exceptions.InferenceError(node=self, context=context) from exc # 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 None yield from assigned.infer(context) found_one = True if found_one: return dict(node=self, context=context) return None 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 None 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 return 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.""" yield from _filter_operation_errors( self, _infer_unaryop, context, util.BadUnaryOperationMessage ) return 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) context = contextmod.bind_context_to_node(context, instance) method = methods[0] inferred = next(method.infer(context=context)) if inferred is util.Uninferable: raise exceptions.InferenceError 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 inference 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 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 infer yet what this is. yield util.Uninferable return yield from results return # The operation doesn't seem to be supported so let the caller know about it yield util.BadBinaryOperationMessage(left_type, binary_opnode.op, right_type) def _infer_binop(self, context): """Binary operation inference logic.""" 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 context = context or contextmod.InferenceContext() lhs_context = contextmod.copy_context(context) rhs_context = contextmod.copy_context(context) lhs_iter = left.infer(context=lhs_context) rhs_iter = right.infer(context=rhs_context) for lhs, rhs in itertools.product(lhs_iter, rhs_iter): if any(value is util.Uninferable for value in (rhs, lhs)): # Don't know how to process this. yield util.Uninferable return try: yield from _infer_binary_operation(lhs, rhs, self, context, _get_binop_flow) 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() rhs_context = context.clone() lhs_iter = self.target.infer_lhs(context=context) rhs_iter = self.value.infer(context=rhs_context) for lhs, rhs in itertools.product(lhs_iter, rhs_iter): if any(value is util.Uninferable for value in (rhs, lhs)): # Don't know how to process this. yield util.Uninferable return try: yield from _infer_binary_operation( left=lhs, right=rhs, binary_opnode=self, context=context, flow_factory=_get_aug_flow, ) except exceptions._NonDeducibleTypeHierarchy: yield util.Uninferable @decorators.raise_if_nothing_inferred @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. @decorators.raise_if_nothing_inferred 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.raise_if_nothing_inferred @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 @decorators.raise_if_nothing_inferred @decorators.path_wrapper def infer_empty_node(self, context=None): if not self.has_underlying_object(): yield util.Uninferable else: try: yield from MANAGER.infer_ast_from_something(self.object, context=context) except exceptions.AstroidError: yield util.Uninferable nodes.EmptyNode._infer = infer_empty_node @decorators.raise_if_nothing_inferred 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 new_context = contextmod.bind_context_to_node(context, self) if not context: context = new_context # Create a new callcontext for providing index as an argument. new_context.callcontext = contextmod.CallContext(args=[index]) method = next(self.igetattr("__getitem__", context=context), None) if not isinstance(method, bases.BoundMethod): raise exceptions.InferenceError( "Could not find __getitem__ for {node!r}.", node=self, context=context ) return next(method.infer_call_result(self, new_context)) bases.Instance.getitem = instance_getitem def _populate_context_lookup(call, context): # Allows context to be saved for later # for inference inside a function context_lookup = {} if context is None: return context_lookup for arg in call.args: if isinstance(arg, nodes.Starred): context_lookup[arg.value] = context else: context_lookup[arg] = context keywords = call.keywords if call.keywords is not None else [] for keyword in keywords: context_lookup[keyword.value] = context return context_lookup