new unused-private-member causes a crash

[stanislavlevin]

Bug description

Given a file test.py:

# Please disable message unrelated to the bug
# pylint: disable=missing-docstring,too-few-public-methods,protected-access
class Context:
    def __init__(self):
        self.__messages = None

class Command:
    def __init__(self):
        self.context = Context()

    def method(self):
        self.context.__messages = []
        for message in self.context.__messages:
            print(message)

(Configuration)

No response

Command used

Result of pylint test.py:

************* Module test
test.py:4:8: W0238: Unused private member `Context.__messages` (unused-private-member)
Exception on node <ClassDef.Command l.6 at 0x7f4ee5bd05e0> in file '/usr/src/RPM/BUILD/test.py'
Traceback (most recent call last):
  File "/usr/bin/pylint.py3", line 33, in <module>
    sys.exit(load_entry_point('pylint==2.8.2', 'console_scripts', 'pylint')())
  File "/usr/src/.local/lib/python3/site-packages/pylint/__init__.py", line 24, in run_pylint
    PylintRun(sys.argv[1:])
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/run.py", line 384, in __init__
    linter.check(args)
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/pylinter.py", line 951, in check
    self._check_files(
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/pylinter.py", line 985, in _check_files
    self._check_file(get_ast, check_astroid_module, name, filepath, modname)
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/pylinter.py", line 1011, in _check_file
    check_astroid_module(ast_node)
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/pylinter.py", line 1145, in check_astroid_module
    retval = self._check_astroid_module(
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/pylinter.py", line 1190, in _check_astroid_module
    walker.walk(ast_node)
  File "/usr/src/.local/lib/python3/site-packages/pylint/utils/ast_walker.py", line 77, in walk
    self.walk(child)
  File "/usr/src/.local/lib/python3/site-packages/pylint/utils/ast_walker.py", line 79, in walk
    callback(astroid)
  File "/usr/src/.local/lib/python3/site-packages/pylint/checkers/classes.py", line 893, in leave_classdef
    self._check_unused_private_members(node)
  File "/usr/src/.local/lib/python3/site-packages/pylint/checkers/classes.py", line 953, in _check_unused_private_members
    and attribute.expr.name == "self"
AttributeError: 'Attribute' object has no attribute 'name'

(Expected behavior)

pylint shouldn't crash.

(Version affected)

pylint 2.9.0+ (including today's main).

(OS / Environment)

ALTLinux

(Additional dependencies)

No response

[stanislavlevin]

traceback for today's main:

************* Module test
test.py:4:8: W0238: Unused private member `Context.__messages` (unused-private-member)
Exception on node <ClassDef.Command l.6 at 0x7feb211e4940> in file '/usr/src/RPM/BUILD/test.py'
Traceback (most recent call last):
  File "/usr/bin/pylint.py3", line 33, in <module>
    sys.exit(load_entry_point('pylint==2.8.2', 'console_scripts', 'pylint')())
  File "/usr/src/.local/lib/python3/site-packages/pylint/__init__.py", line 24, in run_pylint
    PylintRun(sys.argv[1:])
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/run.py", line 384, in __init__
    linter.check(args)
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/pylinter.py", line 975, in check
    self._check_files(
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/pylinter.py", line 1009, in _check_files
    self._check_file(get_ast, check_astroid_module, name, filepath, modname)
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/pylinter.py", line 1035, in _check_file
    check_astroid_module(ast_node)
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/pylinter.py", line 1172, in check_astroid_module
    retval = self._check_astroid_module(
  File "/usr/src/.local/lib/python3/site-packages/pylint/lint/pylinter.py", line 1217, in _check_astroid_module
    walker.walk(ast_node)
  File "/usr/src/.local/lib/python3/site-packages/pylint/utils/ast_walker.py", line 77, in walk
    self.walk(child)
  File "/usr/src/.local/lib/python3/site-packages/pylint/utils/ast_walker.py", line 79, in walk
    callback(astroid)
  File "/usr/src/.local/lib/python3/site-packages/pylint/checkers/classes.py", line 904, in leave_classdef
    self._check_unused_private_attributes(node)
  File "/usr/src/.local/lib/python3/site-packages/pylint/checkers/classes.py", line 983, in _check_unused_private_attributes
    assign_attr.expr.name == "cls"
AttributeError: 'Attribute' object has no attribute 'name'

[stanislavlevin]

IMO, non-current node's private attributes should be skipped.

[yushao2]

hi, looked into it and came up with a PR :) please take a look

[stanislavlevin]

The fix is verified. Thank you! (fixed + no regressions were found)