brain_io.py

# Copyright (c) 2016 Claudiu Popa <pcmanticore@gmail.com>

# 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 brain hints for some of the _io C objects."""

import astroid


BUFFERED = {"BufferedWriter", "BufferedReader"}
TextIOWrapper = "TextIOWrapper"
FileIO = "FileIO"
BufferedWriter = "BufferedWriter"


def _generic_io_transform(node, name, cls):
    """Transform the given name, by adding the given *class* as a member of the node."""

    io_module = astroid.MANAGER.ast_from_module_name("_io")
    attribute_object = io_module[cls]
    instance = attribute_object.instantiate_class()
    node.locals[name] = [instance]


def _transform_text_io_wrapper(node):
    # This is not always correct, since it can vary with the type of the descriptor,
    # being stdout, stderr or stdin. But we cannot get access to the name of the
    # stream, which is why we are using the BufferedWriter class as a default
    # value
    return _generic_io_transform(node, name="buffer", cls=BufferedWriter)


def _transform_buffered(node):
    return _generic_io_transform(node, name="raw", cls=FileIO)


astroid.MANAGER.register_transform(
    astroid.ClassDef, _transform_buffered, lambda node: node.name in BUFFERED
)
astroid.MANAGER.register_transform(
    astroid.ClassDef,
    _transform_text_io_wrapper,
    lambda node: node.name == TextIOWrapper,
)