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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
from __future__ import annotations
from typing import TYPE_CHECKING
from astroid import nodes
from pylint.checkers import BaseChecker
from pylint.checkers.utils import (
PYMETHODS,
decorated_with_property,
is_overload_stub,
is_protocol_class,
overrides_a_method,
)
from pylint.interfaces import INFERENCE
if TYPE_CHECKING:
from pylint.lint.pylinter import PyLinter
class NoSelfUseChecker(BaseChecker):
name = "no_self_use"
msgs = {
"R6301": (
"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.",
{"old_names": [("R0201", "old-no-self-use")]},
),
}
def __init__(self, linter: PyLinter) -> None:
super().__init__(linter)
self._first_attrs: list[str | None] = []
self._meth_could_be_func: bool | None = None
def visit_name(self, node: nodes.Name) -> None:
"""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 visit_functiondef(self, node: nodes.FunctionDef) -> None:
if not node.is_method():
return
self._meth_could_be_func = True
self._check_first_arg_for_type(node)
visit_asyncfunctiondef = visit_functiondef
def _check_first_arg_for_type(self, node: nodes.FunctionDef) -> None:
"""Check the name of first argument."""
# pylint: disable=duplicate-code
if node.args.posonlyargs:
first_arg = node.args.posonlyargs[0].name
elif node.args.args:
first_arg = node.argnames()[0]
else:
first_arg = None
self._first_attrs.append(first_arg)
# static method
if node.type == "staticmethod":
self._first_attrs[-1] = None
def leave_functiondef(self, node: nodes.FunctionDef) -> None:
"""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():
first = self._first_attrs.pop()
if first is None:
return
class_node = node.parent.frame(future=True)
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 _has_bare_super_call(node)
or is_protocol_class(class_node)
or is_overload_stub(node)
)
):
self.add_message("no-self-use", node=node, confidence=INFERENCE)
leave_asyncfunctiondef = leave_functiondef
def _has_bare_super_call(fundef_node: nodes.FunctionDef) -> bool:
for call in fundef_node.nodes_of_class(nodes.Call):
func = call.func
if isinstance(func, nodes.Name) and func.name == "super" and not call.args:
return True
return False
def register(linter: PyLinter) -> None:
linter.register_checker(NoSelfUseChecker(linter))
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