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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 is_none, node_type, only_required_for_messages
if TYPE_CHECKING:
from pylint.lint import PyLinter
class MultipleTypesChecker(BaseChecker):
"""Checks for variable type redefinition (NoneType excepted).
At a function, method, class or module scope
This rule could be improved:
- Currently, if an attribute is set to different types in 2 methods of a
same class, it won't be detected (see functional test)
- One could improve the support for inference on assignment with tuples,
ifexpr, etc. Also, it would be great to have support for inference on
str.split()
"""
name = "multiple_types"
msgs = {
"R0204": (
"Redefinition of %s type from %s to %s",
"redefined-variable-type",
"Used when the type of a variable changes inside a "
"method or a function.",
)
}
def visit_classdef(self, _: nodes.ClassDef) -> None:
self._assigns.append({})
@only_required_for_messages("redefined-variable-type")
def leave_classdef(self, _: nodes.ClassDef) -> None:
self._check_and_add_messages()
visit_functiondef = visit_asyncfunctiondef = visit_classdef
leave_functiondef = leave_asyncfunctiondef = leave_module = leave_classdef
def visit_module(self, _: nodes.Module) -> None:
self._assigns: list[dict[str, list[tuple[nodes.Assign, str]]]] = [{}]
def _check_and_add_messages(self) -> None:
assigns = self._assigns.pop()
for name, args in assigns.items():
if len(args) <= 1:
continue
orig_node, orig_type = args[0]
# Check if there is a type in the following nodes that would be
# different from orig_type.
for redef_node, redef_type in args[1:]:
if redef_type == orig_type:
continue
# if a variable is defined to several types in an if node,
# this is not actually redefining.
orig_parent = orig_node.parent
redef_parent = redef_node.parent
if isinstance(orig_parent, nodes.If):
if orig_parent == redef_parent:
if (
redef_node in orig_parent.orelse
and orig_node not in orig_parent.orelse
):
orig_node, orig_type = redef_node, redef_type
continue
elif isinstance(
redef_parent, nodes.If
) and redef_parent in orig_parent.nodes_of_class(nodes.If):
orig_node, orig_type = redef_node, redef_type
continue
orig_type = orig_type.replace("builtins.", "")
redef_type = redef_type.replace("builtins.", "")
self.add_message(
"redefined-variable-type",
node=redef_node,
args=(name, orig_type, redef_type),
)
break
def visit_assign(self, node: nodes.Assign) -> None:
# we don't handle multiple assignment nor slice assignment
target = node.targets[0]
if isinstance(target, (nodes.Tuple, nodes.Subscript)):
return
# ignore NoneType
if is_none(node):
return
_type = node_type(node.value)
if _type:
self._assigns[-1].setdefault(target.as_string(), []).append(
(node, _type.pytype())
)
def register(linter: PyLinter) -> None:
linter.register_checker(MultipleTypesChecker(linter))
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