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class_checker.py
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class_checker.py
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# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
# Copyright (c) https://github.com/PyCQA/pylint/blob/main/CONTRIBUTORS.txt
"""Classes checker for Python code."""
from __future__ import annotations
import collections
import sys
from collections import defaultdict
from collections.abc import Callable, Sequence
from itertools import chain, zip_longest
from re import Pattern
from typing import TYPE_CHECKING, Any, Union
import astroid
from astroid import bases, nodes
from astroid.nodes import LocalsDictNodeNG
from astroid.typing import SuccessfulInferenceResult
from pylint.checkers import BaseChecker, utils
from pylint.checkers.utils import (
PYMETHODS,
class_is_abstract,
decorated_with,
decorated_with_property,
get_outer_class,
has_known_bases,
is_attr_private,
is_attr_protected,
is_builtin_object,
is_comprehension,
is_iterable,
is_property_setter,
is_property_setter_or_deleter,
node_frame_class,
only_required_for_messages,
safe_infer,
unimplemented_abstract_methods,
uninferable_final_decorators,
)
from pylint.interfaces import HIGH, INFERENCE
from pylint.typing import MessageDefinitionTuple
if TYPE_CHECKING:
from pylint.lint.pylinter import PyLinter
if sys.version_info >= (3, 8):
from functools import cached_property
else:
from astroid.decorators import cachedproperty as cached_property
_AccessNodes = Union[nodes.Attribute, nodes.AssignAttr]
INVALID_BASE_CLASSES = {"bool", "range", "slice", "memoryview"}
BUILTIN_DECORATORS = {"builtins.property", "builtins.classmethod"}
ASTROID_TYPE_COMPARATORS = {
nodes.Const: lambda a, b: a.value == b.value,
nodes.ClassDef: lambda a, b: a.qname == b.qname,
nodes.Tuple: lambda a, b: a.elts == b.elts,
nodes.List: lambda a, b: a.elts == b.elts,
nodes.Dict: lambda a, b: a.items == b.items,
nodes.Name: lambda a, b: set(a.infer()) == set(b.infer()),
}
# 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: nodes.Call) -> _CallSignature:
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, nodes.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, nodes.Name):
kws[arg] = value.name
else:
kws[arg] = None
for arg in call.args:
if isinstance(arg, nodes.Starred) and isinstance(arg.value, nodes.Name):
# Positional variadic and a name, otherwise some transformation
# might have occurred.
starred_args.append(arg.value.name)
elif isinstance(arg, nodes.Name):
args.append(arg.name)
else:
args.append(None)
return _CallSignature(args, kws, starred_args, starred_kws)
def _signature_from_arguments(arguments: nodes.Arguments) -> _ParameterSignature:
kwarg = arguments.kwarg
vararg = arguments.vararg
args = [
arg.name
for arg in chain(arguments.posonlyargs, 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: _ParameterSignature, call: _CallSignature
) -> bool:
"""Check if a definition signature is equivalent to a call."""
if definition.kwargs:
if definition.kwargs not in call.starred_kws:
return False
elif call.starred_kws:
return False
if definition.varargs:
if definition.varargs not in call.starred_args:
return False
elif call.starred_args:
return False
if any(kw not in call.kws for kw in definition.kwonlyargs):
return False
if definition.args != call.args:
return False
# No extra kwargs in call.
return all(kw in call.args or kw in definition.kwonlyargs for kw in call.kws)
def _is_trivial_super_delegation(function: nodes.FunctionDef) -> bool:
"""Check whether a function definition is a method consisting only of a
call to the same function on the superclass.
"""
if (
not function.is_method()
# Adding decorators to a function changes behavior and
# constitutes a non-trivial change.
or function.decorators
):
return False
body = function.body
if len(body) != 1:
# Multiple statements, which means this overridden method
# could do multiple things we are not aware of.
return False
statement = body[0]
if not isinstance(statement, (nodes.Expr, nodes.Return)):
# Doing something else than what we are interested in.
return False
call = statement.value
if (
not isinstance(call, nodes.Call)
# Not a super() attribute access.
or not isinstance(call.func, nodes.Attribute)
):
return False
# Anything other than a super call is non-trivial.
super_call = safe_infer(call.func.expr)
if not isinstance(super_call, astroid.objects.Super):
return False
# The name should be the same.
if call.func.attrname != function.name:
return False
# 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
or not isinstance(super_call.type, astroid.Instance)
or super_call.type.name != current_scope.name
):
return False
return True
# Deal with parameters overriding in two methods.
def _positional_parameters(method: nodes.FunctionDef) -> list[nodes.AssignName]:
positional = method.args.args
if method.is_bound() and method.type in {"classmethod", "method"}:
positional = positional[1:]
return positional # type: ignore[no-any-return]
class _DefaultMissing:
"""Sentinel value for missing arg default, use _DEFAULT_MISSING."""
_DEFAULT_MISSING = _DefaultMissing()
def _has_different_parameters_default_value(
original: nodes.Arguments, overridden: nodes.Arguments
) -> bool:
"""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
for param in chain(original.args, original.kwonlyargs):
try:
original_default = original.default_value(param.name)
except astroid.exceptions.NoDefault:
original_default = _DEFAULT_MISSING
try:
overridden_default = overridden.default_value(param.name)
if original_default is _DEFAULT_MISSING:
# Only the original has a default.
return True
except astroid.exceptions.NoDefault:
if original_default is _DEFAULT_MISSING:
# Both have a default, no difference
continue
# Only the override has a default.
return True
original_type = type(original_default)
if not isinstance(overridden_default, original_type):
# Two args with same name but different types
return True
is_same_fn: Callable[[Any, Any], bool] | None = ASTROID_TYPE_COMPARATORS.get(
original_type
)
if is_same_fn is None:
# If the default value comparison is unhandled, assume the value is different
return True
if not is_same_fn(original_default, overridden_default):
# Two args with same type but different values
return True
return False
def _has_different_parameters(
original: list[nodes.AssignName],
overridden: list[nodes.AssignName],
dummy_parameter_regex: Pattern[str],
) -> list[str]:
result: list[str] = []
zipped = zip_longest(original, overridden)
for original_param, overridden_param in zipped:
if not overridden_param:
return ["Number of parameters "]
if not original_param:
try:
overridden_param.parent.default_value(overridden_param.name)
continue
except astroid.NoDefault:
return ["Number of parameters "]
# check for the arguments' name
names = [param.name for param in (original_param, overridden_param)]
if any(dummy_parameter_regex.match(name) for name in names):
continue
if original_param.name != overridden_param.name:
result.append(
f"Parameter '{original_param.name}' has been renamed "
f"to '{overridden_param.name}' in"
)
return result
def _has_different_keyword_only_parameters(
original: list[nodes.AssignName],
overridden: list[nodes.AssignName],
) -> list[str]:
"""Determine if the two methods have different keyword only parameters."""
original_names = [i.name for i in original]
overridden_names = [i.name for i in overridden]
if any(name not in overridden_names for name in original_names):
return ["Number of parameters "]
for name in overridden_names:
if name in original_names:
continue
try:
overridden[0].parent.default_value(name)
except astroid.NoDefault:
return ["Number of parameters "]
return []
def _different_parameters(
original: nodes.FunctionDef,
overridden: nodes.FunctionDef,
dummy_parameter_regex: Pattern[str],
) -> list[str]:
"""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.
"""
output_messages = []
original_parameters = _positional_parameters(original)
overridden_parameters = _positional_parameters(overridden)
# Copy kwonlyargs list so that we don't affect later function linting
original_kwonlyargs = original.args.kwonlyargs
# Allow positional/keyword variadic in overridden to match against any
# positional/keyword argument in original.
# Keep any arguments that are found separately in overridden to satisfy
# later tests
if overridden.args.vararg:
overridden_names = [v.name for v in overridden_parameters]
original_parameters = [
v for v in original_parameters if v.name in overridden_names
]
if overridden.args.kwarg:
overridden_names = [v.name for v in overridden.args.kwonlyargs]
original_kwonlyargs = [
v for v in original.args.kwonlyargs if v.name in overridden_names
]
different_positional = _has_different_parameters(
original_parameters, overridden_parameters, dummy_parameter_regex
)
different_kwonly = _has_different_keyword_only_parameters(
original_kwonlyargs, overridden.args.kwonlyargs
)
if different_kwonly and different_positional:
if "Number " in different_positional[0] and "Number " in different_kwonly[0]:
output_messages.append("Number of parameters ")
output_messages += different_positional[1:]
output_messages += different_kwonly[1:]
else:
output_messages += different_positional
output_messages += different_kwonly
else:
if different_positional:
output_messages += different_positional
if different_kwonly:
output_messages += different_kwonly
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.
output_messages.clear()
# Arguments will only violate LSP if there are variadics in the original
# that are then removed from the overridden
kwarg_lost = original.args.kwarg and not overridden.args.kwarg
vararg_lost = original.args.vararg and not overridden.args.vararg
if kwarg_lost or vararg_lost:
output_messages += ["Variadics removed in"]
return output_messages
def _is_invalid_base_class(cls: nodes.ClassDef) -> bool:
return cls.name in INVALID_BASE_CLASSES and is_builtin_object(cls)
def _has_data_descriptor(cls: nodes.ClassDef, attr: str) -> bool:
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: LocalsDictNodeNG,
klass: nodes.ClassDef,
methods: Sequence[str],
) -> bool:
"""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, nodes.FunctionDef):
return False
for method in methods:
try:
inferred = klass.getattr(method)
except astroid.NotFoundError:
continue
for infer_method in inferred:
for call in infer_method.nodes_of_class(nodes.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: str, klass: nodes.ClassDef) -> bool:
"""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 = "builtins.property"
for attr in attributes:
if attr is astroid.Uninferable:
continue
try:
inferred = next(attr.infer())
except astroid.InferenceError:
continue
if isinstance(inferred, nodes.FunctionDef) and decorated_with_property(
inferred
):
return True
if inferred.pytype() != property_name:
continue
cls = node_frame_class(inferred)
if cls == klass.declared_metaclass():
continue
return True
return False
def _has_same_layout_slots(
slots: list[nodes.Const | None], assigned_value: nodes.Name
) -> bool:
inferred = next(assigned_value.infer())
if isinstance(inferred, nodes.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 zip_longest(slots, other_slots)
):
return True
return False
MSGS: dict[str, MessageDefinitionTuple] = {
"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 %r 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 %r 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.",
),
"W0221": (
"%s %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. Extra arguments "
"with default values are ignored.",
),
"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 in child class %r",
"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.",
),
"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.",
),
"W0246": (
"Useless parent or super() delegation in method %r",
"useless-parent-delegation",
"Used whenever we can detect that an overridden method is useless, "
"relying on parent or super() delegation to do the same thing as another method "
"from the MRO.",
{"old_names": [("W0235", "useless-super-delegation")]},
),
"W0236": (
"Method %r was expected to be %r, found it instead as %r",
"invalid-overridden-method",
"Used when we detect that a method was overridden in a way "
"that does not match its base class "
"which could result in potential bugs at runtime.",
),
"W0237": (
"%s %s %r method",
"arguments-renamed",
"Used when a method parameter has a different name than in "
"the implemented interface or in an overridden method.",
),
"W0238": (
"Unused private member `%s.%s`",
"unused-private-member",
"Emitted when a private member of a class is defined but not used.",
),
"W0239": (
"Method %r overrides a method decorated with typing.final which is defined in class %r",
"overridden-final-method",
"Used when a method decorated with typing.final has been overridden.",
),
"W0240": (
"Class %r is a subclass of a class decorated with typing.final: %r",
"subclassed-final-class",
"Used when a class decorated with typing.final has been subclassed.",
),
"W0244": (
"Redefined slots %r in subclass",
"redefined-slots-in-subclass",
"Used when a slot is re-defined in a subclass.",
),
"W0245": (
"Super call without brackets",
"super-without-brackets",
"Used when a call to super does not have brackets and thus is not an actual "
"call and does not work as expected.",
),
"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",
"Duplicate use of base classes in derived classes raise TypeErrors.",
),
"E0242": (
"Value %r in slots conflicts with class variable",
"class-variable-slots-conflict",
"Used when a value in __slots__ conflicts with a class variable, property or method.",
),
"E0243": (
"Invalid assignment to '__class__'. Should be a class definition but got a '%s'",
"invalid-class-object",
"Used when an invalid object is assigned to a __class__ property. "
"Only a class is permitted.",
),
"E0244": (
'Extending inherited Enum class "%s"',
"invalid-enum-extension",
"Used when a class tries to extend an inherited Enum class. "
"Doing so will raise a TypeError at runtime.",
),
"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.",
),
"R0205": (
"Class %r inherits from object, can be safely removed from bases in python3",
"useless-object-inheritance",
"Used when a class inherit from object, which under python3 is implicit, "
"hence can be safely removed from bases.",
),
"R0206": (
"Cannot have defined parameters for properties",
"property-with-parameters",
"Used when we detect that a property also has parameters, which are useless, "
"given that properties cannot be called with additional arguments.",
),
}
def _scope_default() -> defaultdict[str, list[_AccessNodes]]:
# It's impossible to nest defaultdicts so we must use a function
return defaultdict(list)
class ScopeAccessMap:
"""Store the accessed variables per scope."""
def __init__(self) -> None:
self._scopes: defaultdict[
nodes.ClassDef, defaultdict[str, list[_AccessNodes]]
] = defaultdict(_scope_default)
def set_accessed(self, node: _AccessNodes) -> None:
"""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: nodes.ClassDef) -> dict[str, list[_AccessNodes]]:
"""Get the accessed variables for the given scope."""
return self._scopes.get(scope, {})
class ClassChecker(BaseChecker):
"""Checker for class nodes.
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
"""
# configuration section name
name = "classes"
# messages
msgs = MSGS
# configuration options
options = (
(
"defining-attr-methods",
{
"default": ("__init__", "__new__", "setUp", "__post_init__"),
"type": "csv",
"metavar": "<method names>",
"help": "List of method names used to declare (i.e. assign) \
instance attributes.",
},
),
(
"valid-classmethod-first-arg",
{
"default": ("cls",),
"type": "csv",
"metavar": "<argument names>",
"help": "List of valid names for the first argument in \
a class method.",
},
),
(
"valid-metaclass-classmethod-first-arg",
{
"default": ("mcs",),
"type": "csv",
"metavar": "<argument names>",
"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": "<protected access exclusions>",
"help": (
"List of member names, which should be excluded "
"from the protected access warning."
),
},
),
(
"check-protected-access-in-special-methods",
{
"default": False,
"type": "yn",
"metavar": "<y or n>",
"help": "Warn about protected attribute access inside special methods",
},
),
)
def __init__(self, linter: PyLinter) -> None:
super().__init__(linter)
self._accessed = ScopeAccessMap()
self._first_attrs: list[str | None] = []
def open(self) -> None:
self._mixin_class_rgx = self.linter.config.mixin_class_rgx
py_version = self.linter.config.py_version
self._py38_plus = py_version >= (3, 8)
@cached_property
def _dummy_rgx(self) -> Pattern[str]:
return self.linter.config.dummy_variables_rgx # type: ignore[no-any-return]
@only_required_for_messages(
"abstract-method",
"invalid-slots",
"single-string-used-for-slots",
"invalid-slots-object",
"class-variable-slots-conflict",
"inherit-non-class",
"useless-object-inheritance",
"inconsistent-mro",
"duplicate-bases",
"redefined-slots-in-subclass",
"invalid-enum-extension",
"subclassed-final-class",
)
def visit_classdef(self, node: nodes.ClassDef) -> None:
"""Init visit variable _accessed."""
self._check_bases_classes(node)
self._check_slots(node)
self._check_proper_bases(node)
self._check_typing_final(node)
self._check_consistent_mro(node)
def _check_consistent_mro(self, node: nodes.ClassDef) -> None:
"""Detect that a class has a consistent mro or duplicate bases."""
try:
node.mro()
except astroid.InconsistentMroError:
self.add_message("inconsistent-mro", args=node.name, node=node)
except astroid.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: nodes.ClassDef) -> None:
"""Detect that a class inherits something which is not
a class or a type.
"""
for base in node.bases:
ancestor = safe_infer(base)
if not ancestor:
continue
if isinstance(ancestor, astroid.Instance) and ancestor.is_subtype_of(
"builtins.type"
):
continue
if not isinstance(ancestor, nodes.ClassDef) or _is_invalid_base_class(
ancestor
):
self.add_message("inherit-non-class", args=base.as_string(), node=node)
if isinstance(ancestor, nodes.ClassDef) and ancestor.is_subtype_of(
"enum.Enum"
):
members = ancestor.getattr("__members__")
if members and isinstance(members[0], nodes.Dict) and members[0].items:
self.add_message(
"invalid-enum-extension",
args=ancestor.name,
node=node,
confidence=INFERENCE,
)
if ancestor.name == object.__name__:
self.add_message(
"useless-object-inheritance", args=node.name, node=node
)
def _check_typing_final(self, node: nodes.ClassDef) -> None:
"""Detect that a class does not subclass a class decorated with
`typing.final`.
"""
if not self._py38_plus:
return
for base in node.bases:
ancestor = safe_infer(base)
if not ancestor:
continue
if isinstance(ancestor, nodes.ClassDef) and (
decorated_with(ancestor, ["typing.final"])
or uninferable_final_decorators(ancestor.decorators)
):
self.add_message(
"subclassed-final-class",
args=(node.name, ancestor.name),
node=node,
)
@only_required_for_messages(
"unused-private-member",
"attribute-defined-outside-init",
"access-member-before-definition",
)
def leave_classdef(self, node: nodes.ClassDef) -> None:
"""Checker for Class nodes.
check that instance attributes are defined in __init__ and check
access to existent members
"""
self._check_unused_private_functions(node)
self._check_unused_private_variables(node)
self._check_unused_private_attributes(node)
self._check_attribute_defined_outside_init(node)
def _check_unused_private_functions(self, node: nodes.ClassDef) -> None:
for function_def in node.nodes_of_class(nodes.FunctionDef):
if not is_attr_private(function_def.name):
continue
parent_scope = function_def.parent.scope()
if isinstance(parent_scope, nodes.FunctionDef):
# Handle nested functions
if function_def.name in (
n.name for n in parent_scope.nodes_of_class(nodes.Name)
):
continue
for child in node.nodes_of_class((nodes.Name, nodes.Attribute)):
# Check for cases where the functions are used as a variable instead of as a method call
if isinstance(child, nodes.Name) and child.name == function_def.name:
break
if isinstance(child, nodes.Attribute):
# Ignore recursive calls
if (
child.attrname != function_def.name
or child.scope() == function_def
):
continue
# Check self.__attrname, cls.__attrname, node_name.__attrname
if isinstance(child.expr, nodes.Name) and child.expr.name in {
"self",
"cls",
node.name,
}:
break
# Check type(self).__attrname
if isinstance(child.expr, nodes.Call):
inferred = safe_infer(child.expr)
if (
isinstance(inferred, nodes.ClassDef)
and inferred.name == node.name
):
break
else:
name_stack = []
curr = parent_scope
# Generate proper names for nested functions
while curr != node:
name_stack.append(curr.name)
curr = curr.parent.scope()
outer_level_names = f"{'.'.join(reversed(name_stack))}"