Duplicates found in MROs (OrderedSet)

[hippo91]

Steps to reproduce

This issue is directly linked to pylint-dev/pylint#4093

1. Write the following module:

from ordered_set import OrderedSet

class RegistryOrderedSet:
    def __init__(self, clazz, type_name="Object"):
        self._objects_dict = defaultdict(OrderedSet)

2. Lint it

Current behavior

Traceback (most recent call last):
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/decorators.py", line 34, in cached
    return cache[func]
KeyError: <bound method ClassDef.slots of <ClassDef.OrderedSet l.55 at 0x7f2517b98dc0>>

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/peillexg/PROGRAMMATION/Python/pylint_sandbox/bug_pylint_4093/test/bin/pylint", line 7, in <module>
    exec(compile(f.read(), __file__, 'exec'))
  File "/home/peillexg/PROGRAMMATION/Python/pylint/bin/pylint", line 5, in <module>
    run_pylint()
  File "/home/peillexg/PROGRAMMATION/Python/pylint/pylint/__init__.py", line 22, in run_pylint
    PylintRun(sys.argv[1:])
  File "/home/peillexg/PROGRAMMATION/Python/pylint/pylint/lint/run.py", line 358, in __init__
    linter.check(args)
  File "/home/peillexg/PROGRAMMATION/Python/pylint/pylint/lint/pylinter.py", line 862, in check
    self._check_files(
  File "/home/peillexg/PROGRAMMATION/Python/pylint/pylint/lint/pylinter.py", line 896, in _check_files
    self._check_file(get_ast, check_astroid_module, name, filepath, modname)
  File "/home/peillexg/PROGRAMMATION/Python/pylint/pylint/lint/pylinter.py", line 922, in _check_file
    check_astroid_module(ast_node)
  File "/home/peillexg/PROGRAMMATION/Python/pylint/pylint/lint/pylinter.py", line 1054, in check_astroid_module
    retval = self._check_astroid_module(
  File "/home/peillexg/PROGRAMMATION/Python/pylint/pylint/lint/pylinter.py", line 1099, in _check_astroid_module
    walker.walk(ast_node)
  File "/home/peillexg/PROGRAMMATION/Python/pylint/pylint/utils/ast_walker.py", line 75, in walk
    self.walk(child)
  File "/home/peillexg/PROGRAMMATION/Python/pylint/pylint/utils/ast_walker.py", line 72, in walk
    callback(astroid)
  File "/home/peillexg/PROGRAMMATION/Python/pylint/pylint/checkers/variables.py", line 1182, in visit_importfrom
    module = node.do_import_module(name_parts[0])
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/mixins.py", line 99, in do_import_module
    return mymodule.import_module(
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/scoped_nodes.py", line 646, in import_module
    return MANAGER.ast_from_module_name(absmodname)
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/manager.py", line 191, in ast_from_module_name
    return self.ast_from_file(found_spec.location, modname, fallback=False)
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/manager.py", line 100, in ast_from_file
    return AstroidBuilder(self).file_build(filepath, modname)
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/builder.py", line 139, in file_build
    return self._post_build(module, encoding)
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/builder.py", line 159, in _post_build
    self.delayed_assattr(delayed)
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/builder.py", line 235, in delayed_assattr
    if not _can_assign_attr(inferred, node.attrname):
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/builder.py", line 60, in _can_assign_attr
    slots = node.slots()
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/decorators.py", line 36, in cached
    cache[func] = result = func(*args, **kwargs)
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/scoped_nodes.py", line 2838, in slots
    slots = list(grouped_slots())
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/scoped_nodes.py", line 2823, in grouped_slots
    for cls in self.mro()[:-1]:
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/scoped_nodes.py", line 2909, in mro
    return self._compute_mro(context=context)
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/scoped_nodes.py", line 2898, in _compute_mro
    unmerged_mro = list(clean_duplicates_mro(unmerged_mro, self, context))
  File "/home/peillexg/PROGRAMMATION/Python/astroid/astroid/scoped_nodes.py", line 110, in clean_duplicates_mro
    raise exceptions.DuplicateBasesError(
astroid.exceptions.DuplicateBasesError: Duplicates found in MROs (OrderedSet), (_GenericAlias, _Final, object), (_GenericAlias, _Final, object), (_GenericAlias, _GenericAlias) for <ClassDef.OrderedSet l.55 at 0x7f2517b98dc0>

Expected behavior

No error. It was the case with astroid 2.4.2. A bisection leads to commit 7f1d513.

python -c "from astroid import __pkginfo__; print(__pkginfo__.version)" output

2.5

[cdce8p]

Found a similar issue with aiohttp.

pylint 2.7.0
astroid 1.5.0

Interestingly the error occurred when using Python 3.8. However, 3.9 was fine.

# test_pylint.py

# pylint: disable=missing-class-docstring,inherit-non-class,too-few-public-methods
# pylint: disable=no-value-for-parameter,unused-import,missing-module-docstring
# pylint: disable=super-init-not-called
import abc
from typing import Sized, Iterable


class AbstractRoute(abc.ABC):
    pass


class AbstractResource(Sized, Iterable["AbstractRoute"]):
    pass


class IndexView(AbstractResource):
    def __init__(self):
        self.var = 1

Running pylint test.py results in

Traceback (most recent call last):
  File ".../astroid/astroid/decorators.py", line 34, in cached
    return cache[func]
KeyError: <bound method ClassDef.slots of <ClassDef.IndexView l.16 at 0x7fdfae20e460>>

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File ".../pylint/pylint/lint/pylinter.py", line 1030, in get_ast
    return MANAGER.ast_from_file(filepath, modname, source=True)
  File ".../astroid/astroid/manager.py", line 100, in ast_from_file
    return AstroidBuilder(self).file_build(filepath, modname)
  File ".../astroid/astroid/builder.py", line 138, in file_build
    return self._post_build(module, encoding)
  File ".../astroid/astroid/builder.py", line 158, in _post_build
    self.delayed_assattr(delayed)
  File ".../astroid/astroid/builder.py", line 234, in delayed_assattr
    if not _can_assign_attr(inferred, node.attrname):
  File ".../astroid/astroid/builder.py", line 59, in _can_assign_attr
    slots = node.slots()
  File ".../astroid/astroid/decorators.py", line 36, in cached
    cache[func] = result = func(*args, **kwargs)
  File ".../astroid/astroid/scoped_nodes.py", line 2834, in slots
    slots = list(grouped_slots())
  File ".../astroid/astroid/scoped_nodes.py", line 2819, in grouped_slots
    for cls in self.mro()[:-1]:
  File ".../astroid/astroid/scoped_nodes.py", line 2905, in mro
    return self._compute_mro(context=context)
  File ".../astroid/astroid/scoped_nodes.py", line 2882, in _compute_mro
    mro = base._compute_mro(context=context)
  File ".../astroid/astroid/scoped_nodes.py", line 2894, in _compute_mro
    unmerged_mro = list(clean_duplicates_mro(unmerged_mro, self, context))
  File ".../astroid/astroid/scoped_nodes.py", line 109, in clean_duplicates_mro
    raise exceptions.DuplicateBasesError(
astroid.exceptions.DuplicateBasesError: Duplicates found in MROs (AbstractResource), (_GenericAlias, _Final, object), (_GenericAlias, _Final, object), (_GenericAlias, _GenericAlias) for <ClassDef.AbstractResource l.12 at 0x7fdfae20e250>.
************* Module test_pylint
test_pylint.py:1:0: F0002: <class 'astroid.exceptions.DuplicateBasesError'>: Duplicates found in MROs (AbstractResource), (_GenericAlias, _Final, object), (_GenericAlias, _Final, object), (_GenericAlias, _GenericAlias) for <ClassDef.AbstractResource l.12 at 0x7fdfae20e250>. (astroid-error)

[cdce8p]

One solution might be to add an additional condition to the check in clean_duplicates_mro to filter for typing._GenericAlias:
https://github.com/PyCQA/astroid/blob/5192907ff22fc0383206c0e5bbe3e1635d6c7132/astroid/scoped_nodes.py#L102-L110

Replacing L108 with

        if (
            names
            and names[0] is not None
            and last_index[names[0]] != 0
            and names[0][1] != "typing._GenericAlias"
        ):

does work. I just don't know enough about the way astroid works to know if that's a good fix.

--

As for Python 3.9: There it seems to be typing._BaseGenericAlias and typing._SpecialGenericAlias which previously was just typing._GenericAlias.

[cdce8p]

@hippo91 I opened #910 to hopefully fix this issue.