brain_attrs.py

# Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html
# For details: https://github.com/PyCQA/astroid/blob/master/COPYING.LESSER
"""
Astroid hook for the attrs library

Without this hook pylint reports unsupported-assignment-operation
for attrs classes
"""

import astroid
from astroid import MANAGER


ATTRIB_NAMES = frozenset(("attr.ib", "attrib", "attr.attrib"))
ATTRS_NAMES = frozenset(("attr.s", "attrs", "attr.attrs", "attr.attributes"))


def is_decorated_with_attrs(node, decorator_names=ATTRS_NAMES):
    """Return True if a decorated node has
    an attr decorator applied."""
    if not node.decorators:
        return False
    for decorator_attribute in node.decorators.nodes:
        if isinstance(decorator_attribute, astroid.Call):  # decorator with arguments
            decorator_attribute = decorator_attribute.func
        if decorator_attribute.as_string() in decorator_names:
            return True
    return False


def attr_attributes_transform(node):
    """Given that the ClassNode has an attr decorator,
    rewrite class attributes as instance attributes
    """
    # Astroid can't infer this attribute properly
    # Prevents https://github.com/PyCQA/pylint/issues/1884
    node.locals["__attrs_attrs__"] = [astroid.Unknown(parent=node)]

    for cdefbodynode in node.body:
        if not isinstance(cdefbodynode, (astroid.Assign, astroid.AnnAssign)):
            continue
        if isinstance(cdefbodynode.value, astroid.Call):
            if cdefbodynode.value.func.as_string() not in ATTRIB_NAMES:
                continue
        else:
            continue
        targets = (
            cdefbodynode.targets
            if hasattr(cdefbodynode, "targets")
            else [cdefbodynode.target]
        )
        for target in targets:

            rhs_node = astroid.Unknown(
                lineno=cdefbodynode.lineno,
                col_offset=cdefbodynode.col_offset,
                parent=cdefbodynode,
            )
            node.locals[target.name] = [rhs_node]
            node.instance_attrs[target.name] = [rhs_node]


MANAGER.register_transform(
    astroid.ClassDef, attr_attributes_transform, is_decorated_with_attrs
)