astroid/interpreter/dunder_lookup.py

# Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html
# For details: https://github.com/pylint-dev/astroid/blob/main/LICENSE
# Copyright (c) https://github.com/pylint-dev/astroid/blob/main/CONTRIBUTORS.txt

"""Contains logic for retrieving special methods.

This implementation does not rely on the dot attribute access
logic, found in ``.getattr()``. The difference between these two
is that the dunder methods are looked with the type slots
(you can find more about these here
http://lucumr.pocoo.org/2014/8/16/the-python-i-would-like-to-see/)
As such, the lookup for the special methods is actually simpler than
the dot attribute access.
"""

from __future__ import annotations

import itertools
from typing import TYPE_CHECKING

import astroid
from astroid import nodes
from astroid.exceptions import AttributeInferenceError

if TYPE_CHECKING:
    from astroid.context import InferenceContext


def _lookup_in_mro(node, name) -> list:
    attrs = node.locals.get(name, [])

    nodes_ = itertools.chain.from_iterable(
        ancestor.locals.get(name, []) for ancestor in node.ancestors(recurs=True)
    )
    values = list(itertools.chain(attrs, nodes_))
    if not values:
        raise AttributeInferenceError(attribute=name, target=node)

    return values


def lookup(
    node: nodes.NodeNG, name: str, context: InferenceContext | None = None
) -> list:
    """Lookup the given special method name in the given *node*.

    If the special method was found, then a list of attributes
    will be returned. Otherwise, `astroid.AttributeInferenceError`
    is going to be raised.
    """
    if isinstance(node, (nodes.List, nodes.Tuple, nodes.Const, nodes.Dict, nodes.Set)):
        return _builtin_lookup(node, name)
    if isinstance(node, astroid.Instance):
        return _lookup_in_mro(node, name)
    if isinstance(node, nodes.ClassDef):
        return _class_lookup(node, name, context=context)

    raise AttributeInferenceError(attribute=name, target=node)


def _class_lookup(
    node: nodes.ClassDef, name: str, context: InferenceContext | None = None
) -> list:
    metaclass = node.metaclass(context=context)
    if metaclass is None:
        raise AttributeInferenceError(attribute=name, target=node)

    return _lookup_in_mro(metaclass, name)


def _builtin_lookup(node, name) -> list:
    values = node.locals.get(name, [])
    if not values:
        raise AttributeInferenceError(attribute=name, target=node)

    return values