# 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 . """this module contains a set of functions to handle inference on astroid trees """ # pylint: disable=no-value-for-parameter; Pylint FP #629, please remove afterwards. 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 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.List._infer = infer_end nodes.Tuple._infer = infer_end nodes.Dict._infer = infer_end nodes.Set._infer = infer_end nodes.Slice._infer = infer_end 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 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=name, context=context)) nodes.Global._infer = infer_global _SLICE_SENTINEL = object() def _slice_value(index, context=None): """Get the value of the given slice index.""" if isinstance(index, nodes.Const): if isinstance(index.value, (int, type(None))): return index.value elif index is None: return None else: # Try to infer what the index actually is. # Since we can't return all the possible values, # we'll stop at the first possible value. try: inferred = next(index.infer(context=context)) except exceptions.InferenceError: pass else: if isinstance(inferred, nodes.Const): if isinstance(inferred.value, (int, type(None))): return inferred.value # Use a sentinel, because None can be a valid # value that this function can return, # as it is the case for unspecified bounds. return _SLICE_SENTINEL @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 if value.__class__ == bases.Instance: index_value = index else: index_value = _SLICE_SENTINEL if isinstance(index, nodes.Const): index_value = index.value elif isinstance(index, nodes.Slice): # Infer slices from the original object. lower = _slice_value(index.lower, context) upper = _slice_value(index.upper, context) step = _slice_value(index.step, context) if all(elem is not _SLICE_SENTINEL for elem in (lower, upper, step)): index_value = slice(lower, upper, step) elif isinstance(index, bases.Instance): index = helpers.class_instance_as_index(index) if index: index_value = index.value else: raise exceptions.InferenceError(node=self, context=context) if index_value is _SLICE_SENTINEL: raise exceptions.InferenceError(node=self, context=context) try: assigned = value.getitem(index_value, context) except (IndexError, TypeError, 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): # The operation was used on something which # doesn't support it. yield util.BadUnaryOperationMessage(operand, self.op, exc) continue try: meth = operand.getattr(meth, context=context)[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, op, other, context, method_name): """Invoke binary operation inference on the given instance.""" method = instance.getattr(method_name)[0] inferred = next(method.infer(context=context)) return instance.infer_binary_op(op, other, context, inferred) def _aug_op(instance, 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, other=other, context=context, method_name=method_name) def _bin_op(instance, 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, 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, op, 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) """ if _same_type(left_type, right_type): methods = [_bin_op(left, op, right, context)] elif helpers.is_subtype(left_type, right_type): methods = [_bin_op(left, op, right, context)] elif helpers.is_supertype(left_type, right_type): methods = [_bin_op(right, op, left, reverse_context, reverse=True), _bin_op(left, op, right, context)] else: methods = [_bin_op(left, op, right, context), _bin_op(right, op, left, reverse_context, reverse=True)] return methods def _get_aug_flow(left, left_type, aug_op, 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) """ op = aug_op.strip("=") if _same_type(left_type, right_type): methods = [_aug_op(left, aug_op, right, context), _bin_op(left, op, right, context)] elif helpers.is_subtype(left_type, right_type): methods = [_aug_op(left, aug_op, right, context), _bin_op(left, op, right, context)] elif helpers.is_supertype(left_type, right_type): methods = [_aug_op(left, aug_op, right, context), _bin_op(right, op, left, reverse_context, reverse=True), _bin_op(left, op, right, context)] else: methods = [_aug_op(left, aug_op, right, context), _bin_op(left, op, right, context), _bin_op(right, op, left, reverse_context, reverse=True)] return methods def _infer_binary_operation(left, right, op, 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, op, 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 inferrence 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, 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 op = self.op # 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 results = _infer_binary_operation(lhs, rhs, op, context, _get_binop_flow) for result in results: yield result @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): """Inferrence logic for augmented binary operations.""" if context is None: context = contextmod.InferenceContext() op = self.op 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 # inferrence 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 results = _infer_binary_operation(lhs, rhs, op, context, _get_aug_flow) 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