AttributeError: 'Subscript' object has no attribute 'name'

[MrTrick]

Seems distinct from #2250
Maybe a regression, or another edge case?

Steps to reproduce

Given a file a.py:

from attr import attrs, attrib
from typing import Optional

@attrs()
class User:
    name: str = attrib()
    age: int = attrib()
    occupation = Optional[str] = attrib(default=None)

Where a typo was made in the last line - first = should be :.

Current behavior

Pylint crashes if executed on the file, or on any file that imports it.

# pylint a.py
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/pylint/lint/pylinter.py", line 1041, in get_ast
    return MANAGER.ast_from_file(filepath, modname, source=True)
  File "/usr/local/lib/python3.7/site-packages/astroid/manager.py", line 98, in ast_from_file
    return AstroidBuilder(self).file_build(filepath, modname)
  File "/usr/local/lib/python3.7/site-packages/astroid/builder.py", line 142, in file_build
    return self._post_build(module, encoding)
  File "/usr/local/lib/python3.7/site-packages/astroid/builder.py", line 166, in _post_build
    module = self._manager.visit_transforms(module)
  File "/usr/local/lib/python3.7/site-packages/astroid/manager.py", line 75, in visit_transforms
    return self._transform.visit(node)
  File "/usr/local/lib/python3.7/site-packages/astroid/transforms.py", line 90, in visit
    module.body = [self._visit(child) for child in module.body]
  File "/usr/local/lib/python3.7/site-packages/astroid/transforms.py", line 90, in <listcomp>
    module.body = [self._visit(child) for child in module.body]
  File "/usr/local/lib/python3.7/site-packages/astroid/transforms.py", line 58, in _visit
    return self._transform(node)
  File "/usr/local/lib/python3.7/site-packages/astroid/transforms.py", line 41, in _transform
    ret = transform_func(node)
  File "/usr/local/lib/python3.7/site-packages/astroid/brain/brain_attrs.py", line 58, in attr_attributes_transform
    node.locals[target.name] = [rhs_node]
AttributeError: 'Subscript' object has no attribute 'name'
************* Module a
a.py:1:0: F0002: <class 'AttributeError'>: 'Subscript' object has no attribute 'name' (astroid-error)

Additionally: If you run pylint b.py where b.py is:

from a import User

The error message does not mention a.py at all:

Exception on node <ImportFrom l.3 at 0x7fe42b22d490> in file '/tmp/b.py'
Traceback (most recent call last):
<SNIP>
AttributeError: 'Subscript' object has no attribute 'name'

Expected behavior

Should catch and report the problem, not crash. Perhaps:

************* Module a
a.py:8:13: E1137: 'Optional' does not support item assignment (unsupported-assignment-operation)

pylint --version output

Result of pylint --version output:

# pylint --version
pylint 3.0.0a3
astroid 2.5.6
Python 3.7.7 (default, Apr 16 2020, 18:55:06)
[GCC 8.3.0]

Additional dependencies

attrs==19.3.0

[Pierre-Sassoulas]

Look like we're affected in our own merge request (#4422)

[FrankyBoy]

Same error, different location:

Traceback (most recent call last):
  File "/path/to/venv/bin/pylint", line 8, in <module>
    sys.exit(run_pylint())
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/__init__.py", line 24, in run_pylint
    PylintRun(sys.argv[1:])
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/lint/run.py", line 384, in __init__
    linter.check(args)
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/lint/pylinter.py", line 973, in check
    self._check_files(
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/lint/pylinter.py", line 1007, in _check_files
    self._check_file(get_ast, check_astroid_module, name, filepath, modname)
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/lint/pylinter.py", line 1033, in _check_file
    check_astroid_module(ast_node)
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/lint/pylinter.py", line 1170, in check_astroid_module
    retval = self._check_astroid_module(
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/lint/pylinter.py", line 1215, in _check_astroid_module
    walker.walk(ast_node)
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/utils/ast_walker.py", line 77, in walk
    self.walk(child)
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/utils/ast_walker.py", line 79, in walk
    callback(astroid)
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/checkers/classes.py", line 903, in leave_classdef
    self._check_unused_private_attributes(node)
  File "/path/to/venv/lib64/python3.9/site-packages/pylint/checkers/classes.py", line 966, in _check_unused_private_attributes
    and attribute.expr.name == assign_attr.expr.name
AttributeError: 'Subscript' object has no attribute 'name'

pylint --version:
pylint 2.9.3
astroid 2.6.2
Python 3.9.5 (default, May 05 2021, 15:23:13) [GCC]

[Pierre-Sassoulas]

@FrankyBoy could you open another issue and provide the code or a snippet that is making pylint crash, please ?

[Pierre-Sassoulas]

Sorry I thought this issue was closed, no need to create a new one.

[FrankyBoy]

Heh, forgot to exclude the venv from my scan, and this failure actually comes from some library code ... it's pyparsing (venv/lib/python3.9/site-packages/pyparsing.py). Installed version is 2.4.7. Sadly this is some minified file so I can't really give any more concrete pointers right now :/