# -*- coding: utf-8 -*- # Copyright (c) 2006-2016 LOGILAB S.A. (Paris, FRANCE) # Copyright (c) 2010 Maarten ter Huurne # Copyright (c) 2012-2014 Google, Inc. # Copyright (c) 2012 FELD Boris # Copyright (c) 2013-2017 Claudiu Popa # Copyright (c) 2014 Michal Nowikowski # Copyright (c) 2014 Brett Cannon # Copyright (c) 2014 Arun Persaud # Copyright (c) 2014 David Pursehouse # Copyright (c) 2015 Dmitry Pribysh # Copyright (c) 2015 Ionel Cristian Maries # Copyright (c) 2016-2017 Łukasz Rogalski # Copyright (c) 2016 Alexander Todorov # Copyright (c) 2016 Anthony Foglia # Copyright (c) 2016 Florian Bruhin # Copyright (c) 2016 Moises Lopez # Copyright (c) 2016 Jakub Wilk # Copyright (c) 2017 hippo91 # Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html # For details: https://github.com/PyCQA/pylint/blob/master/COPYING """classes checker for Python code """ from __future__ import generators import collections import sys import six import astroid from astroid.bases import Generator, BUILTINS from astroid.exceptions import InconsistentMroError, DuplicateBasesError from astroid import decorators from astroid import objects from astroid.scoped_nodes import function_to_method from pylint.interfaces import IAstroidChecker from pylint.checkers import BaseChecker from pylint.checkers.utils import ( PYMETHODS, SPECIAL_METHODS_PARAMS, overrides_a_method, check_messages, is_attr_private, is_attr_protected, node_frame_class, is_builtin_object, decorated_with_property, unimplemented_abstract_methods, decorated_with, class_is_abstract, safe_infer, has_known_bases, is_iterable, is_comprehension) from pylint.utils import get_global_option if sys.version_info >= (3, 0): NEXT_METHOD = '__next__' else: NEXT_METHOD = 'next' INVALID_BASE_CLASSES = {'bool', 'range', 'slice', 'memoryview'} # Dealing with useless override detection, with regard # to parameters vs arguments _CallSignature = collections.namedtuple( '_CallSignature', 'args kws starred_args starred_kws') _ParameterSignature = collections.namedtuple( '_ParameterSignature', 'args kwonlyargs varargs kwargs', ) def _signature_from_call(call): kws = {} args = [] starred_kws = [] starred_args = [] for keyword in call.keywords or []: arg, value = keyword.arg, keyword.value if arg is None and isinstance(value, astroid.Name): # Starred node and we are interested only in names, # otherwise some transformation might occur for the parameter. starred_kws.append(value.name) elif isinstance(value, astroid.Name): kws[arg] = value.name else: kws[arg] = None for arg in call.args: if isinstance(arg, astroid.Starred) and isinstance(arg.value, astroid.Name): # Positional variadic and a name, otherwise some transformation # might have occurred. starred_args.append(arg.value.name) elif isinstance(arg, astroid.Name): args.append(arg.name) else: args.append(None) return _CallSignature(args, kws, starred_args, starred_kws) def _signature_from_arguments(arguments): kwarg = arguments.kwarg vararg = arguments.vararg args = [arg.name for arg in arguments.args if arg.name != 'self'] kwonlyargs = [arg.name for arg in arguments.kwonlyargs] return _ParameterSignature(args, kwonlyargs, vararg, kwarg) def _definition_equivalent_to_call(definition, call): '''Check if a definition signature is equivalent to a call.''' if definition.kwargs: same_kw_variadics = definition.kwargs in call.starred_kws else: same_kw_variadics = not call.starred_kws if definition.varargs: same_args_variadics = definition.varargs in call.starred_args else: same_args_variadics = not call.starred_args same_kwonlyargs = all(kw in call.kws for kw in definition.kwonlyargs) same_args = definition.args == call.args no_additional_kwarg_arguments = True if call.kws: for keyword in call.kws: is_arg = keyword in call.args is_kwonly = keyword in definition.kwonlyargs if not is_arg and not is_kwonly: # Maybe this argument goes into **kwargs, # or it is an extraneous argument. # In any case, the signature is different than # the call site, which stops our search. no_additional_kwarg_arguments = False break return all(( same_args, same_kwonlyargs, same_args_variadics, same_kw_variadics, no_additional_kwarg_arguments, )) # Deal with parameters overridding in two methods. def _positional_parameters(method): positional = method.args.args if method.type in ('classmethod', 'method'): positional = positional[1:] return positional def _get_node_type(node, potential_types): """ Return the type of the node if it exists in potential_types. Args: node (astroid.node): node to get the type of. potential_types (tuple): potential types of the node. Returns: type: type of the node or None. """ for potential_type in potential_types: if isinstance(node, potential_type): return potential_type return None def _check_arg_equality(node_a, node_b, attr_name): """ Check equality of nodes based on the comparison of their attributes named attr_name. Args: node_a (astroid.node): first node to compare. node_b (astroid.node): second node to compare. attr_name (str): name of the nodes attribute to use for comparison. Returns: bool: True if node_a.attr_name == node_b.attr_name, False otherwise. """ return getattr(node_a, attr_name) == getattr(node_b, attr_name) def _has_different_parameters_default_value(original, overridden): """ Check if original and overridden methods arguments have different default values Return True if one of the overridden arguments has a default value different from the default value of the original argument If one of the method doesn't have argument (.args is None) return False """ if original.args is None or overridden.args is None: return False original_param_names = [param.name for param in original.args] default_missing = object() for param_name in original_param_names: try: original_default = original.default_value(param_name) except astroid.exceptions.NoDefault: original_default = default_missing try: overridden_default = overridden.default_value(param_name) except astroid.exceptions.NoDefault: overridden_default = default_missing default_list = [arg == default_missing for arg in (original_default, overridden_default)] if any(default_list) and not all(default_list): # Only one arg has no default value return True astroid_type_compared_attr = {astroid.Const: "value", astroid.ClassDef: "name", astroid.Tuple: "elts", astroid.List: "elts"} handled_types = tuple(astroid_type for astroid_type in astroid_type_compared_attr) original_type = _get_node_type(original_default, handled_types) if original_type: # We handle only astroid types that are inside the dict astroid_type_compared_attr if not isinstance(overridden_default, original_type): # Two args with same name but different types return True if not _check_arg_equality(original_default, overridden_default, astroid_type_compared_attr[original_type]): # Two args with same type but different values return True return False def _has_different_parameters(original, overridden, dummy_parameter_regex): zipped = six.moves.zip_longest(original, overridden) for original_param, overridden_param in zipped: params = (original_param, overridden_param) if not all(params): return True names = [param.name for param in params] if any(map(dummy_parameter_regex.match, names)): continue if original_param.name != overridden_param.name: return True return False def _different_parameters(original, overridden, dummy_parameter_regex): """Determine if the two methods have different parameters They are considered to have different parameters if: * they have different positional parameters, including different names * one of the methods is having variadics, while the other is not * they have different keyword only parameters. """ original_parameters = _positional_parameters(original) overridden_parameters = _positional_parameters(overridden) different_positional = _has_different_parameters( original_parameters, overridden_parameters, dummy_parameter_regex) different_kwonly = _has_different_parameters( original.args.kwonlyargs, overridden.args.kwonlyargs, dummy_parameter_regex) if original.name in PYMETHODS: # Ignore the difference for special methods. If the parameter # numbers are different, then that is going to be caught by # unexpected-special-method-signature. # If the names are different, it doesn't matter, since they can't # be used as keyword arguments anyway. different_positional = different_kwonly = False # Both or none should have extra variadics, otherwise the method # loses or gains capabilities that are not reflected into the parent method, # leading to potential inconsistencies in the code. different_kwarg = sum( 1 for param in (original.args.kwarg, overridden.args.kwarg) if not param) == 1 different_vararg = sum( 1 for param in (original.args.vararg, overridden.args.vararg) if not param) == 1 return any(( different_positional, different_kwarg, different_vararg, different_kwonly )) def _is_invalid_base_class(cls): return cls.name in INVALID_BASE_CLASSES and is_builtin_object(cls) def _has_data_descriptor(cls, attr): attributes = cls.getattr(attr) for attribute in attributes: try: for inferred in attribute.infer(): if isinstance(inferred, astroid.Instance): try: inferred.getattr('__get__') inferred.getattr('__set__') except astroid.NotFoundError: continue else: return True except astroid.InferenceError: # Can't infer, avoid emitting a false positive in this case. return True return False def _called_in_methods(func, klass, methods): """ Check if the func was called in any of the given methods, belonging to the *klass*. Returns True if so, False otherwise. """ if not isinstance(func, astroid.FunctionDef): return False for method in methods: try: infered = klass.getattr(method) except astroid.NotFoundError: continue for infer_method in infered: for call in infer_method.nodes_of_class(astroid.Call): try: bound = next(call.func.infer()) except (astroid.InferenceError, StopIteration): continue if not isinstance(bound, astroid.BoundMethod): continue func_obj = bound._proxied if isinstance(func_obj, astroid.UnboundMethod): func_obj = func_obj._proxied if func_obj.name == func.name: return True return False def _is_attribute_property(name, klass): """ Check if the given attribute *name* is a property in the given *klass*. It will look for `property` calls or for functions with the given name, decorated by `property` or `property` subclasses. Returns ``True`` if the name is a property in the given klass, ``False`` otherwise. """ try: attributes = klass.getattr(name) except astroid.NotFoundError: return False property_name = "{0}.property".format(BUILTINS) for attr in attributes: try: infered = next(attr.infer()) except astroid.InferenceError: continue if (isinstance(infered, astroid.FunctionDef) and decorated_with_property(infered)): return True if infered.pytype() == property_name: return True return False def _has_bare_super_call(fundef_node): for call in fundef_node.nodes_of_class(astroid.Call): func = call.func if (isinstance(func, astroid.Name) and func.name == 'super' and not call.args): return True return False def _safe_infer_call_result(node, caller, context=None): """ Safely infer the return value of a function. Returns None if inference failed or if there is some ambiguity (more than one node has been inferred). Otherwise returns infered value. """ try: inferit = node.infer_call_result(caller, context=context) value = next(inferit) except astroid.InferenceError: return None # inference failed except StopIteration: return None # no values infered try: next(inferit) return None # there is ambiguity on the inferred node except astroid.InferenceError: return None # there is some kind of ambiguity except StopIteration: return value def _has_same_layout_slots(slots, assigned_value): inferred = next(assigned_value.infer()) if isinstance(inferred, astroid.ClassDef): other_slots = inferred.slots() if all(first_slot and second_slot and first_slot.value == second_slot.value for (first_slot, second_slot) in six.moves.zip_longest(slots, other_slots)): return True return False MSGS = { 'F0202': ('Unable to check methods signature (%s / %s)', 'method-check-failed', 'Used when Pylint has been unable to check methods signature ' 'compatibility for an unexpected reason. Please report this kind ' 'if you don\'t make sense of it.'), 'E0202': ('An attribute defined in %s line %s hides this method', 'method-hidden', 'Used when a class defines a method which is hidden by an ' 'instance attribute from an ancestor class or set by some ' 'client code.'), 'E0203': ('Access to member %r before its definition line %s', 'access-member-before-definition', 'Used when an instance member is accessed before it\'s actually ' 'assigned.'), 'W0201': ('Attribute %r defined outside __init__', 'attribute-defined-outside-init', 'Used when an instance attribute is defined outside the __init__ ' 'method.'), 'W0212': ('Access to a protected member %s of a client class', # E0214 'protected-access', 'Used when a protected member (i.e. class member with a name ' 'beginning with an underscore) is access outside the class or a ' 'descendant of the class where it\'s defined.'), 'E0211': ('Method has no argument', 'no-method-argument', 'Used when a method which should have the bound instance as ' 'first argument has no argument defined.'), 'E0213': ('Method should have "self" as first argument', 'no-self-argument', 'Used when a method has an attribute different the "self" as ' 'first argument. This is considered as an error since this is ' 'a so common convention that you shouldn\'t break it!'), 'C0202': ('Class method %s should have %s as first argument', 'bad-classmethod-argument', 'Used when a class method has a first argument named differently ' 'than the value specified in valid-classmethod-first-arg option ' '(default to "cls"), recommended to easily differentiate them ' 'from regular instance methods.'), 'C0203': ('Metaclass method %s should have %s as first argument', 'bad-mcs-method-argument', 'Used when a metaclass method has a first argument named ' 'differently than the value specified in valid-classmethod-first' '-arg option (default to "cls"), recommended to easily ' 'differentiate them from regular instance methods.'), 'C0204': ('Metaclass class method %s should have %s as first argument', 'bad-mcs-classmethod-argument', 'Used when a metaclass class method has a first argument named ' 'differently than the value specified in valid-metaclass-' 'classmethod-first-arg option (default to "mcs"), recommended to ' 'easily differentiate them from regular instance methods.'), 'W0211': ('Static method with %r as first argument', 'bad-staticmethod-argument', 'Used when a static method has "self" or a value specified in ' 'valid-classmethod-first-arg option or ' 'valid-metaclass-classmethod-first-arg option as first argument.' ), 'R0201': ('Method could be a function', 'no-self-use', 'Used when a method doesn\'t use its bound instance, and so could ' 'be written as a function.' ), 'W0221': ('Parameters differ from %s %r method', 'arguments-differ', 'Used when a method has a different number of arguments than in ' 'the implemented interface or in an overridden method.'), 'W0222': ('Signature differs from %s %r method', 'signature-differs', 'Used when a method signature is different than in the ' 'implemented interface or in an overridden method.'), 'W0223': ('Method %r is abstract in class %r but is not overridden', 'abstract-method', 'Used when an abstract method (i.e. raise NotImplementedError) is ' 'not overridden in concrete class.' ), 'W0231': ('__init__ method from base class %r is not called', 'super-init-not-called', 'Used when an ancestor class method has an __init__ method ' 'which is not called by a derived class.'), 'W0232': ('Class has no __init__ method', 'no-init', 'Used when a class has no __init__ method, neither its parent ' 'classes.'), 'W0233': ('__init__ method from a non direct base class %r is called', 'non-parent-init-called', 'Used when an __init__ method is called on a class which is not ' 'in the direct ancestors for the analysed class.'), 'W0235': ('Useless super delegation in method %r', 'useless-super-delegation', 'Used whenever we can detect that an overridden method is useless, ' 'relying on super() delegation to do the same thing as another method ' 'from the MRO.'), 'E0236': ('Invalid object %r in __slots__, must contain ' 'only non empty strings', 'invalid-slots-object', 'Used when an invalid (non-string) object occurs in __slots__.'), 'E0237': ('Assigning to attribute %r not defined in class slots', 'assigning-non-slot', 'Used when assigning to an attribute not defined ' 'in the class slots.'), 'E0238': ('Invalid __slots__ object', 'invalid-slots', 'Used when an invalid __slots__ is found in class. ' 'Only a string, an iterable or a sequence is permitted.'), 'E0239': ('Inheriting %r, which is not a class.', 'inherit-non-class', 'Used when a class inherits from something which is not a ' 'class.'), 'E0240': ('Inconsistent method resolution order for class %r', 'inconsistent-mro', 'Used when a class has an inconsistent method resolution order.'), 'E0241': ('Duplicate bases for class %r', 'duplicate-bases', 'Used when a class has duplicate bases.'), 'R0202': ('Consider using a decorator instead of calling classmethod', 'no-classmethod-decorator', 'Used when a class method is defined without using the decorator ' 'syntax.'), 'R0203': ('Consider using a decorator instead of calling staticmethod', 'no-staticmethod-decorator', 'Used when a static method is defined without using the decorator ' 'syntax.'), 'C0205': ('Class __slots__ should be a non-string iterable', 'single-string-used-for-slots', 'Used when a class __slots__ is a simple string, rather ' 'than an iterable.'), } class ScopeAccessMap(object): """Store the accessed variables per scope.""" def __init__(self): self._scopes = collections.defaultdict( lambda: collections.defaultdict(list) ) def set_accessed(self, node): """Set the given node as accessed.""" frame = node_frame_class(node) if frame is None: # The node does not live in a class. return self._scopes[frame][node.attrname].append(node) def accessed(self, scope): """Get the accessed variables for the given scope.""" return self._scopes.get(scope, {}) class ClassChecker(BaseChecker): """checks for : * methods without self as first argument * overridden methods signature * access only to existent members via self * attributes not defined in the __init__ method * unreachable code """ __implements__ = (IAstroidChecker,) # configuration section name name = 'classes' # messages msgs = MSGS priority = -2 # configuration options options = (('defining-attr-methods', {'default' : ('__init__', '__new__', 'setUp'), 'type' : 'csv', 'metavar' : '', 'help' : 'List of method names used to declare (i.e. assign) \ instance attributes.'} ), ('valid-classmethod-first-arg', {'default' : ('cls',), 'type' : 'csv', 'metavar' : '', 'help' : 'List of valid names for the first argument in \ a class method.'} ), ('valid-metaclass-classmethod-first-arg', {'default' : ('mcs',), 'type' : 'csv', 'metavar' : '', 'help' : 'List of valid names for the first argument in \ a metaclass class method.'} ), ('exclude-protected', { 'default': ( # namedtuple public API. '_asdict', '_fields', '_replace', '_source', '_make'), 'type': 'csv', 'metavar': '', 'help': ('List of member names, which should be excluded ' 'from the protected access warning.')} )) def __init__(self, linter=None): BaseChecker.__init__(self, linter) self._accessed = ScopeAccessMap() self._first_attrs = [] self._meth_could_be_func = None @decorators.cachedproperty def _dummy_rgx(self): return get_global_option( self, 'dummy-variables-rgx', default=None) @decorators.cachedproperty def _ignore_mixin(self): return get_global_option( self, 'ignore-mixin-members', default=True) def visit_classdef(self, node): """init visit variable _accessed """ self._check_bases_classes(node) # if not an exception or a metaclass if node.type == 'class' and has_known_bases(node): try: node.local_attr('__init__') except astroid.NotFoundError: self.add_message('no-init', args=node, node=node) self._check_slots(node) self._check_proper_bases(node) self._check_consistent_mro(node) def _check_consistent_mro(self, node): """Detect that a class has a consistent mro or duplicate bases.""" try: node.mro() except InconsistentMroError: self.add_message('inconsistent-mro', args=node.name, node=node) except DuplicateBasesError: self.add_message('duplicate-bases', args=node.name, node=node) except NotImplementedError: # Old style class, there's no mro so don't do anything. pass def _check_proper_bases(self, node): """ Detect that a class inherits something which is not a class or a type. """ for base in node.bases: ancestor = safe_infer(base) if ancestor in (astroid.YES, None): continue if (isinstance(ancestor, astroid.Instance) and ancestor.is_subtype_of('%s.type' % (BUILTINS,))): continue if (not isinstance(ancestor, astroid.ClassDef) or _is_invalid_base_class(ancestor)): self.add_message('inherit-non-class', args=base.as_string(), node=node) def leave_classdef(self, cnode): """close a class node: check that instance attributes are defined in __init__ and check access to existent members """ # check access to existent members on non metaclass classes if self._ignore_mixin and cnode.name[-5:].lower() == 'mixin': # We are in a mixin class. No need to try to figure out if # something is missing, since it is most likely that it will # miss. return accessed = self._accessed.accessed(cnode) if cnode.type != 'metaclass': self._check_accessed_members(cnode, accessed) # checks attributes are defined in an allowed method such as __init__ if not self.linter.is_message_enabled('attribute-defined-outside-init'): return defining_methods = self.config.defining_attr_methods current_module = cnode.root() for attr, nodes in six.iteritems(cnode.instance_attrs): # skip nodes which are not in the current module and it may screw up # the output, while it's not worth it nodes = [n for n in nodes if not isinstance(n.statement(), (astroid.Delete, astroid.AugAssign)) and n.root() is current_module] if not nodes: continue # error detected by typechecking # check if any method attr is defined in is a defining method if any(node.frame().name in defining_methods for node in nodes): continue # check attribute is defined in a parent's __init__ for parent in cnode.instance_attr_ancestors(attr): attr_defined = False # check if any parent method attr is defined in is a defining method for node in parent.instance_attrs[attr]: if node.frame().name in defining_methods: attr_defined = True if attr_defined: # we're done :) break else: # check attribute is defined as a class attribute try: cnode.local_attr(attr) except astroid.NotFoundError: for node in nodes: if node.frame().name not in defining_methods: # If the attribute was set by a call in any # of the defining methods, then don't emit # the warning. if _called_in_methods(node.frame(), cnode, defining_methods): continue self.add_message('attribute-defined-outside-init', args=attr, node=node) def visit_functiondef(self, node): """check method arguments, overriding""" # ignore actual functions if not node.is_method(): return self._check_useless_super_delegation(node) klass = node.parent.frame() self._meth_could_be_func = True # check first argument is self if this is actually a method self._check_first_arg_for_type(node, klass.type == 'metaclass') if node.name == '__init__': self._check_init(node) return # check signature if the method overloads inherited method for overridden in klass.local_attr_ancestors(node.name): # get astroid for the searched method try: meth_node = overridden[node.name] except KeyError: # we have found the method but it's not in the local # dictionary. # This may happen with astroid build from living objects continue if not isinstance(meth_node, astroid.FunctionDef): continue self._check_signature(node, meth_node, 'overridden', klass) break if node.decorators: for decorator in node.decorators.nodes: if isinstance(decorator, astroid.Attribute) and \ decorator.attrname in ('getter', 'setter', 'deleter'): # attribute affectation will call this method, not hiding it return if isinstance(decorator, astroid.Name) and decorator.name == 'property': # attribute affectation will either call a setter or raise # an attribute error, anyway not hiding the function return # check if the method is hidden by an attribute try: overridden = klass.instance_attr(node.name)[0] # XXX overridden_frame = overridden.frame() if (isinstance(overridden_frame, astroid.FunctionDef) and overridden_frame.type == 'method'): overridden_frame = overridden_frame.parent.frame() if (isinstance(overridden_frame, astroid.ClassDef) and klass.is_subtype_of(overridden_frame.qname())): args = (overridden.root().name, overridden.fromlineno) self.add_message('method-hidden', args=args, node=node) except astroid.NotFoundError: pass visit_asyncfunctiondef = visit_functiondef def _check_useless_super_delegation(self, function): '''Check if the given function node is an useless method override We consider it *useless* if it uses the super() builtin, but having nothing additional whatsoever than not implementing the method at all. If the method uses super() to delegate an operation to the rest of the MRO, and if the method called is the same as the current one, the arguments passed to super() are the same as the parameters that were passed to this method, then the method could be removed altogether, by letting other implementation to take precedence. ''' if not function.is_method(): return if function.decorators: # With decorators is a change of use return body = function.body if len(body) != 1: # Multiple statements, which means this overridden method # could do multiple things we are not aware of. return statement = body[0] if not isinstance(statement, (astroid.Expr, astroid.Return)): # Doing something else than what we are interested into. return call = statement.value if not isinstance(call, astroid.Call): return if not isinstance(call.func, astroid.Attribute): # Not a super() attribute access. return # Should be a super call. try: super_call = next(call.func.expr.infer()) except astroid.InferenceError: return else: if not isinstance(super_call, objects.Super): return # The name should be the same. if call.func.attrname != function.name: return # Should be a super call with the MRO pointer being the current class # and the type being the current instance. current_scope = function.parent.scope() if super_call.mro_pointer != current_scope: return if not isinstance(super_call.type, astroid.Instance): return if super_call.type.name != current_scope.name: return # Check values of default args klass = function.parent.frame() for overridden in klass.local_attr_ancestors(function.name): # get astroid for the searched method try: meth_node = overridden[function.name] except KeyError: # we have found the method but it's not in the local # dictionary. # This may happen with astroid build from living objects continue if not isinstance(meth_node, astroid.FunctionDef): # If the method have an ancestor which is not a function # then it is legitimate to redefine it return if _has_different_parameters_default_value(meth_node.args, function.args): return else: break # Detect if the parameters are the same as the call's arguments. params = _signature_from_arguments(function.args) args = _signature_from_call(call) if _definition_equivalent_to_call(params, args): self.add_message('useless-super-delegation', node=function, args=(function.name, )) def _check_slots(self, node): if '__slots__' not in node.locals: return for slots in node.igetattr('__slots__'): # check if __slots__ is a valid type if slots is astroid.YES: continue if not is_iterable(slots) and not is_comprehension(slots): self.add_message('invalid-slots', node=node) continue if isinstance(slots, astroid.Const): # a string, ignore the following checks self.add_message('single-string-used-for-slots', node=node) continue if not hasattr(slots, 'itered'): # we can't obtain the values, maybe a .deque? continue if isinstance(slots, astroid.Dict): values = [item[0] for item in slots.items] else: values = slots.itered() if values is astroid.YES: return for elt in values: try: self._check_slots_elt(elt) except astroid.InferenceError: continue def _check_slots_elt(self, elt): for infered in elt.infer(): if infered is astroid.Uninferable: continue if (not isinstance(infered, astroid.Const) or not isinstance(infered.value, six.string_types)): self.add_message('invalid-slots-object', args=infered.as_string(), node=elt) continue if not infered.value: self.add_message('invalid-slots-object', args=infered.as_string(), node=elt) def leave_functiondef(self, node): """on method node, check if this method couldn't be a function ignore class, static and abstract methods, initializer, methods overridden from a parent class. """ if node.is_method(): if node.args.args is not None: self._first_attrs.pop() if not self.linter.is_message_enabled('no-self-use'): return class_node = node.parent.frame() if (self._meth_could_be_func and node.type == 'method' and node.name not in PYMETHODS and not (node.is_abstract() or overrides_a_method(class_node, node.name) or decorated_with_property(node) or (six.PY3 and _has_bare_super_call(node)))): self.add_message('no-self-use', node=node) def visit_attribute(self, node): """check if the getattr is an access to a class member if so, register it. Also check for access to protected class member from outside its class (but ignore __special__ methods) """ # Check self if self._uses_mandatory_method_param(node): self._accessed.set_accessed(node) return if not self.linter.is_message_enabled('protected-access'): return self._check_protected_attribute_access(node) def visit_assignattr(self, node): if (isinstance(node.assign_type(), astroid.AugAssign) and self._uses_mandatory_method_param(node)): self._accessed.set_accessed(node) self._check_in_slots(node) def _check_in_slots(self, node): """ Check that the given AssignAttr node is defined in the class slots. """ infered = safe_infer(node.expr) if infered and isinstance(infered, astroid.Instance): klass = infered._proxied if '__slots__' not in klass.locals or not klass.newstyle: return slots = klass.slots() if slots is None: return # If any ancestor doesn't use slots, the slots # defined for this class are superfluous. if any('__slots__' not in ancestor.locals and ancestor.name != 'object' for ancestor in klass.ancestors()): return if not any(slot.value == node.attrname for slot in slots): # If we have a '__dict__' in slots, then # assigning any name is valid. if not any(slot.value == '__dict__' for slot in slots): if _is_attribute_property(node.attrname, klass): # Properties circumvent the slots mechanism, # so we should not emit a warning for them. return if (node.attrname in klass.locals and _has_data_descriptor(klass, node.attrname)): # Descriptors circumvent the slots mechanism as well. return if (node.attrname == '__class__' and _has_same_layout_slots(slots, node.parent.value)): return self.add_message('assigning-non-slot', args=(node.attrname, ), node=node) @check_messages('protected-access', 'no-classmethod-decorator', 'no-staticmethod-decorator') def visit_assign(self, assign_node): self._check_classmethod_declaration(assign_node) node = assign_node.targets[0] if not isinstance(node, astroid.AssignAttr): return if self._uses_mandatory_method_param(node): return self._check_protected_attribute_access(node) def _check_classmethod_declaration(self, node): """Checks for uses of classmethod() or staticmethod() When a @classmethod or @staticmethod decorator should be used instead. A message will be emitted only if the assignment is at a class scope and only if the classmethod's argument belongs to the class where it is defined. `node` is an assign node. """ if not isinstance(node.value, astroid.Call): return # check the function called is "classmethod" or "staticmethod" func = node.value.func if (not isinstance(func, astroid.Name) or func.name not in ('classmethod', 'staticmethod')): return msg = ('no-classmethod-decorator' if func.name == 'classmethod' else 'no-staticmethod-decorator') # assignment must be at a class scope parent_class = node.scope() if not isinstance(parent_class, astroid.ClassDef): return # Check if the arg passed to classmethod is a class member classmeth_arg = node.value.args[0] if not isinstance(classmeth_arg, astroid.Name): return method_name = classmeth_arg.name if any(method_name == member.name for member in parent_class.mymethods()): self.add_message(msg, node=node.targets[0]) def _check_protected_attribute_access(self, node): '''Given an attribute access node (set or get), check if attribute access is legitimate. Call _check_first_attr with node before calling this method. Valid cases are: * self._attr in a method or cls._attr in a classmethod. Checked by _check_first_attr. * Klass._attr inside "Klass" class. * Klass2._attr inside "Klass" class when Klass2 is a base class of Klass. ''' attrname = node.attrname if (is_attr_protected(attrname) and attrname not in self.config.exclude_protected): klass = node_frame_class(node) # XXX infer to be more safe and less dirty ?? # in classes, check we are not getting a parent method # through the class object or through super callee = node.expr.as_string() # We are not in a class, no remaining valid case if klass is None: self.add_message('protected-access', node=node, args=attrname) return # If the expression begins with a call to super, that's ok. if isinstance(node.expr, astroid.Call) and \ isinstance(node.expr.func, astroid.Name) and \ node.expr.func.name == 'super': return # If the expression begins with a call to type(self), that's ok. if self._is_type_self_call(node.expr): return # We are in a class, one remaining valid cases, Klass._attr inside # Klass if not (callee == klass.name or callee in klass.basenames): # Detect property assignments in the body of the class. # This is acceptable: # # class A: # b = property(lambda: self._b) stmt = node.parent.statement() if (isinstance(stmt, astroid.Assign) and len(stmt.targets) == 1 and isinstance(stmt.targets[0], astroid.AssignName)): name = stmt.targets[0].name if _is_attribute_property(name, klass): return self.add_message('protected-access', node=node, args=attrname) def _is_type_self_call(self, expr): return (isinstance(expr, astroid.Call) and isinstance(expr.func, astroid.Name) and expr.func.name == 'type' and len(expr.args) == 1 and self._is_mandatory_method_param(expr.args[0])) def visit_name(self, node): """check if the name handle an access to a class member if so, register it """ if self._first_attrs and (node.name == self._first_attrs[-1] or not self._first_attrs[-1]): self._meth_could_be_func = False def _check_accessed_members(self, node, accessed): """check that accessed members are defined""" # XXX refactor, probably much simpler now that E0201 is in type checker excs = ('AttributeError', 'Exception', 'BaseException') for attr, nodes in six.iteritems(accessed): try: # is it a class attribute ? node.local_attr(attr) # yes, stop here continue except astroid.NotFoundError: pass # is it an instance attribute of a parent class ? try: next(node.instance_attr_ancestors(attr)) # yes, stop here continue except StopIteration: pass # is it an instance attribute ? try: defstmts = node.instance_attr(attr) except astroid.NotFoundError: pass else: # filter out augment assignment nodes defstmts = [stmt for stmt in defstmts if stmt not in nodes] if not defstmts: # only augment assignment for this node, no-member should be # triggered by the typecheck checker continue # filter defstmts to only pick the first one when there are # several assignments in the same scope scope = defstmts[0].scope() defstmts = [stmt for i, stmt in enumerate(defstmts) if i == 0 or stmt.scope() is not scope] # if there are still more than one, don't attempt to be smarter # than we can be if len(defstmts) == 1: defstmt = defstmts[0] # check that if the node is accessed in the same method as # it's defined, it's accessed after the initial assignment frame = defstmt.frame() lno = defstmt.fromlineno for _node in nodes: if _node.frame() is frame and _node.fromlineno < lno \ and not astroid.are_exclusive(_node.statement(), defstmt, excs): self.add_message('access-member-before-definition', node=_node, args=(attr, lno)) def _check_first_arg_for_type(self, node, metaclass=0): """check the name of first argument, expect: * 'self' for a regular method * 'cls' for a class method or a metaclass regular method (actually valid-classmethod-first-arg value) * 'mcs' for a metaclass class method (actually valid-metaclass-classmethod-first-arg) * not one of the above for a static method """ # don't care about functions with unknown argument (builtins) if node.args.args is None: return first_arg = node.args.args and node.argnames()[0] self._first_attrs.append(first_arg) first = self._first_attrs[-1] # static method if node.type == 'staticmethod': if (first_arg == 'self' or first_arg in self.config.valid_classmethod_first_arg or first_arg in self.config.valid_metaclass_classmethod_first_arg): self.add_message('bad-staticmethod-argument', args=first, node=node) return self._first_attrs[-1] = None # class / regular method with no args elif not node.args.args: self.add_message('no-method-argument', node=node) # metaclass elif metaclass: # metaclass __new__ or classmethod if node.type == 'classmethod': self._check_first_arg_config( first, self.config.valid_metaclass_classmethod_first_arg, node, 'bad-mcs-classmethod-argument', node.name) # metaclass regular method else: self._check_first_arg_config( first, self.config.valid_classmethod_first_arg, node, 'bad-mcs-method-argument', node.name) # regular class else: # class method if node.type == 'classmethod': self._check_first_arg_config( first, self.config.valid_classmethod_first_arg, node, 'bad-classmethod-argument', node.name) # regular method without self as argument elif first != 'self': self.add_message('no-self-argument', node=node) def _check_first_arg_config(self, first, config, node, message, method_name): if first not in config: if len(config) == 1: valid = repr(config[0]) else: valid = ', '.join(repr(v) for v in config[:-1]) valid = '%s or %r' % (valid, config[-1]) self.add_message(message, args=(method_name, valid), node=node) def _check_bases_classes(self, node): """check that the given class node implements abstract methods from base classes """ def is_abstract(method): return method.is_abstract(pass_is_abstract=False) # check if this class abstract if class_is_abstract(node): return methods = sorted( unimplemented_abstract_methods(node, is_abstract).items(), key=lambda item: item[0], ) for name, method in methods: owner = method.parent.frame() if owner is node: continue # owner is not this class, it must be a parent class # check that the ancestor's method is not abstract if name in node.locals: # it is redefined as an attribute or with a descriptor continue self.add_message('abstract-method', node=node, args=(name, owner.name)) def _check_init(self, node): """check that the __init__ method call super or ancestors'__init__ method """ if (not self.linter.is_message_enabled('super-init-not-called') and not self.linter.is_message_enabled('non-parent-init-called')): return klass_node = node.parent.frame() to_call = _ancestors_to_call(klass_node) not_called_yet = dict(to_call) for stmt in node.nodes_of_class(astroid.Call): expr = stmt.func if not isinstance(expr, astroid.Attribute) \ or expr.attrname != '__init__': continue # skip the test if using super if isinstance(expr.expr, astroid.Call) and \ isinstance(expr.expr.func, astroid.Name) and \ expr.expr.func.name == 'super': return try: for klass in expr.expr.infer(): if klass is astroid.Uninferable: continue # The infered klass can be super(), which was # assigned to a variable and the `__init__` # was called later. # # base = super() # base.__init__(...) if (isinstance(klass, astroid.Instance) and isinstance(klass._proxied, astroid.ClassDef) and is_builtin_object(klass._proxied) and klass._proxied.name == 'super'): return elif isinstance(klass, objects.Super): return try: del not_called_yet[klass] except KeyError: if klass not in to_call: self.add_message('non-parent-init-called', node=expr, args=klass.name) except astroid.InferenceError: continue for klass, method in six.iteritems(not_called_yet): cls = node_frame_class(method) if klass.name == 'object' or (cls and cls.name == 'object'): continue self.add_message('super-init-not-called', args=klass.name, node=node) def _check_signature(self, method1, refmethod, class_type, cls): """check that the signature of the two given methods match """ if not (isinstance(method1, astroid.FunctionDef) and isinstance(refmethod, astroid.FunctionDef)): self.add_message('method-check-failed', args=(method1, refmethod), node=method1) return instance = cls.instantiate_class() method1 = function_to_method(method1, instance) refmethod = function_to_method(refmethod, instance) # Don't care about functions with unknown argument (builtins). if method1.args.args is None or refmethod.args.args is None: return # Ignore private to class methods. if is_attr_private(method1.name): return # Ignore setters, they have an implicit extra argument, # which shouldn't be taken in consideration. if method1.decorators: for decorator in method1.decorators.nodes: if (isinstance(decorator, astroid.Attribute) and decorator.attrname == 'setter'): return if _different_parameters( refmethod, method1, dummy_parameter_regex=self._dummy_rgx): self.add_message('arguments-differ', args=(class_type, method1.name), node=method1) elif len(method1.args.defaults) < len(refmethod.args.defaults): self.add_message('signature-differs', args=(class_type, method1.name), node=method1) def _uses_mandatory_method_param(self, node): """Check that attribute lookup name use first attribute variable name Name is `self` for method, `cls` for classmethod and `mcs` for metaclass. """ return self._is_mandatory_method_param(node.expr) def _is_mandatory_method_param(self, node): """Check if astroid.Name corresponds to first attribute variable name Name is `self` for method, `cls` for classmethod and `mcs` for metaclass. """ return (self._first_attrs and isinstance(node, astroid.Name) and node.name == self._first_attrs[-1]) class SpecialMethodsChecker(BaseChecker): """Checker which verifies that special methods are implemented correctly. """ __implements__ = (IAstroidChecker, ) name = 'classes' msgs = { 'E0301': ('__iter__ returns non-iterator', 'non-iterator-returned', 'Used when an __iter__ method returns something which is not an ' 'iterable (i.e. has no `%s` method)' % NEXT_METHOD, {'old_names': [('W0234', 'non-iterator-returned'), ('E0234', 'non-iterator-returned')]}), 'E0302': ('The special method %r expects %s param(s), %d %s given', 'unexpected-special-method-signature', 'Emitted when a special method was defined with an ' 'invalid number of parameters. If it has too few or ' 'too many, it might not work at all.', {'old_names': [('E0235', 'bad-context-manager')]}), 'E0303': ('__len__ does not return non-negative integer', 'invalid-length-returned', 'Used when an __len__ method returns something which is not a ' 'non-negative integer', {}), } priority = -2 @check_messages('unexpected-special-method-signature', 'non-iterator-returned', 'invalid-length-returned') def visit_functiondef(self, node): if not node.is_method(): return if node.name == '__iter__': self._check_iter(node) if node.name == '__len__': self._check_len(node) if node.name in PYMETHODS: self._check_unexpected_method_signature(node) visit_asyncfunctiondef = visit_functiondef def _check_unexpected_method_signature(self, node): expected_params = SPECIAL_METHODS_PARAMS[node.name] if expected_params is None: # This can support a variable number of parameters. return if not node.args.args and not node.args.vararg: # Method has no parameter, will be caught # by no-method-argument. return if decorated_with(node, [BUILTINS + ".staticmethod"]): # We expect to not take in consideration self. all_args = node.args.args else: all_args = node.args.args[1:] mandatory = len(all_args) - len(node.args.defaults) optional = len(node.args.defaults) current_params = mandatory + optional if isinstance(expected_params, tuple): # The expected number of parameters can be any value from this # tuple, although the user should implement the method # to take all of them in consideration. emit = mandatory not in expected_params expected_params = "between %d or %d" % expected_params else: # If the number of mandatory parameters doesn't # suffice, the expected parameters for this # function will be deduced from the optional # parameters. rest = expected_params - mandatory if rest == 0: emit = False elif rest < 0: emit = True elif rest > 0: emit = not ((optional - rest) >= 0 or node.args.vararg) if emit: verb = "was" if current_params <= 1 else "were" self.add_message('unexpected-special-method-signature', args=(node.name, expected_params, current_params, verb), node=node) @staticmethod def _is_iterator(node): if node is astroid.YES: # Just ignore YES objects. return True if isinstance(node, Generator): # Generators can be itered. return True if isinstance(node, astroid.Instance): try: node.local_attr(NEXT_METHOD) return True except astroid.NotFoundError: pass elif isinstance(node, astroid.ClassDef): metaclass = node.metaclass() if metaclass and isinstance(metaclass, astroid.ClassDef): try: metaclass.local_attr(NEXT_METHOD) return True except astroid.NotFoundError: pass return False def _check_iter(self, node): infered = _safe_infer_call_result(node, node) if infered is not None: if not self._is_iterator(infered): self.add_message('non-iterator-returned', node=node) def _check_len(self, node): inferred = _safe_infer_call_result(node, node) if not inferred or inferred is astroid.Uninferable: return if (isinstance(inferred, astroid.Instance) and inferred.name == 'int' and not isinstance(inferred, astroid.Const)): # Assume it's good enough, since the int() call might wrap # something that's uninferable for us return if not isinstance(inferred, astroid.Const): self.add_message('invalid-length-returned', node=node) return value = inferred.value if not isinstance(value, six.integer_types) or value < 0: self.add_message('invalid-length-returned', node=node) def _ancestors_to_call(klass_node, method='__init__'): """return a dictionary where keys are the list of base classes providing the queried method, and so that should/may be called from the method node """ to_call = {} for base_node in klass_node.ancestors(recurs=False): try: to_call[base_node] = next(base_node.igetattr(method)) except astroid.InferenceError: continue return to_call def node_method(node, method_name): """get astroid for on the given class node, ensuring it is a Function node """ for node_attr in node.local_attr(method_name): if isinstance(node_attr, astroid.Function): return node_attr raise astroid.NotFoundError(method_name) def register(linter): """required method to auto register this checker """ linter.register_checker(ClassChecker(linter)) linter.register_checker(SpecialMethodsChecker(linter))