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# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/pylint-dev/pylint/blob/main/LICENSE
# Copyright (c) https://github.com/pylint-dev/pylint/blob/main/CONTRIBUTORS.txt
from __future__ import annotations
from typing import TYPE_CHECKING
from astroid import Instance, nodes
from astroid.util import UninferableBase
from pylint.checkers import BaseChecker
from pylint.checkers.utils import safe_infer
from pylint.constants import DUNDER_METHODS
from pylint.interfaces import HIGH
if TYPE_CHECKING:
from pylint.lint import PyLinter
class DunderCallChecker(BaseChecker):
"""Check for unnecessary dunder method calls.
Docs: https://docs.python.org/3/reference/datamodel.html#basic-customization
We exclude names in list pylint.constants.EXTRA_DUNDER_METHODS such as
__index__ (see https://github.com/pylint-dev/pylint/issues/6795)
since these either have no alternative method of being called or
have a genuine use case for being called manually.
Additionally, we exclude classes that are not instantiated since these
might be used to access the dunder methods of a base class of an instance.
We also exclude dunder method calls on super() since
these can't be written in an alternative manner.
"""
name = "unnecessary-dunder-call"
priority = -1
msgs = {
"C2801": (
"Unnecessarily calls dunder method %s. %s.",
"unnecessary-dunder-call",
"Used when a dunder method is manually called instead "
"of using the corresponding function/method/operator.",
),
}
options = ()
def open(self) -> None:
self._dunder_methods: dict[str, str] = {}
for since_vers, dunder_methods in DUNDER_METHODS.items():
if since_vers <= self.linter.config.py_version:
self._dunder_methods.update(dunder_methods)
@staticmethod
def within_dunder_def(node: nodes.NodeNG) -> bool:
"""Check if dunder method call is within a dunder method definition."""
parent = node.parent
while parent is not None:
if (
isinstance(parent, nodes.FunctionDef)
and parent.name.startswith("__")
and parent.name.endswith("__")
):
return True
parent = parent.parent
return False
def visit_call(self, node: nodes.Call) -> None:
"""Check if method being called is an unnecessary dunder method."""
if (
isinstance(node.func, nodes.Attribute)
and node.func.attrname in self._dunder_methods
and not self.within_dunder_def(node)
and not (
isinstance(node.func.expr, nodes.Call)
and isinstance(node.func.expr.func, nodes.Name)
and node.func.expr.func.name == "super"
)
):
inf_expr = safe_infer(node.func.expr)
if not (
inf_expr is None or isinstance(inf_expr, (Instance, UninferableBase))
):
# Skip dunder calls to non instantiated classes.
return
self.add_message(
"unnecessary-dunder-call",
node=node,
args=(node.func.attrname, self._dunder_methods[node.func.attrname]),
confidence=HIGH,
)
def register(linter: PyLinter) -> None:
linter.register_checker(DunderCallChecker(linter))
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