src/attr/_funcs.py

from __future__ import absolute_import, division, print_function

import copy

from ._compat import iteritems
from ._make import NOTHING, _obj_setattr, fields
from .exceptions import AttrsAttributeNotFoundError


def asdict(
    inst,
    recurse=True,
    filter=None,
    dict_factory=dict,
    retain_collection_types=False,
):
    """
    Return the ``attrs`` attribute values of *inst* as a dict.

    Optionally recurse into other ``attrs``-decorated classes.

    :param inst: Instance of an ``attrs``-decorated class.
    :param bool recurse: Recurse into classes that are also
        ``attrs``-decorated.
    :param callable filter: A callable whose return code determines whether an
        attribute or element is included (``True``) or dropped (``False``).  Is
        called with the :class:`attr.Attribute` as the first argument and the
        value as the second argument.
    :param callable dict_factory: A callable to produce dictionaries from.  For
        example, to produce ordered dictionaries instead of normal Python
        dictionaries, pass in ``collections.OrderedDict``.
    :param bool retain_collection_types: Do not convert to ``list`` when
        encountering an attribute whose type is ``tuple`` or ``set``.  Only
        meaningful if ``recurse`` is ``True``.

    :rtype: return type of *dict_factory*

    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
        class.

    ..  versionadded:: 16.0.0 *dict_factory*
    ..  versionadded:: 16.1.0 *retain_collection_types*
    """
    attrs = fields(inst.__class__)
    rv = dict_factory()
    for a in attrs:
        v = getattr(inst, a.name)
        if filter is not None and not filter(a, v):
            continue
        if recurse is True:
            if has(v.__class__):
                rv[a.name] = asdict(
                    v, True, filter, dict_factory, retain_collection_types
                )
            elif isinstance(v, (tuple, list, set)):
                cf = v.__class__ if retain_collection_types is True else list
                rv[a.name] = cf(
                    [
                        _asdict_anything(
                            i, filter, dict_factory, retain_collection_types
                        )
                        for i in v
                    ]
                )
            elif isinstance(v, dict):
                df = dict_factory
                rv[a.name] = df(
                    (
                        _asdict_anything(
                            kk, filter, df, retain_collection_types
                        ),
                        _asdict_anything(
                            vv, filter, df, retain_collection_types
                        ),
                    )
                    for kk, vv in iteritems(v)
                )
            else:
                rv[a.name] = v
        else:
            rv[a.name] = v
    return rv


def _asdict_anything(val, filter, dict_factory, retain_collection_types):
    """
    ``asdict`` only works on attrs instances, this works on anything.
    """
    if getattr(val.__class__, "__attrs_attrs__", None) is not None:
        # Attrs class.
        rv = asdict(val, True, filter, dict_factory, retain_collection_types)
    elif isinstance(val, (tuple, list, set)):
        cf = val.__class__ if retain_collection_types is True else list
        rv = cf(
            [
                _asdict_anything(
                    i, filter, dict_factory, retain_collection_types
                )
                for i in val
            ]
        )
    elif isinstance(val, dict):
        df = dict_factory
        rv = df(
            (
                _asdict_anything(kk, filter, df, retain_collection_types),
                _asdict_anything(vv, filter, df, retain_collection_types),
            )
            for kk, vv in iteritems(val)
        )
    else:
        rv = val
    return rv


def astuple(
    inst,
    recurse=True,
    filter=None,
    tuple_factory=tuple,
    retain_collection_types=False,
):
    """
    Return the ``attrs`` attribute values of *inst* as a tuple.

    Optionally recurse into other ``attrs``-decorated classes.

    :param inst: Instance of an ``attrs``-decorated class.
    :param bool recurse: Recurse into classes that are also
        ``attrs``-decorated.
    :param callable filter: A callable whose return code determines whether an
        attribute or element is included (``True``) or dropped (``False``).  Is
        called with the :class:`attr.Attribute` as the first argument and the
        value as the second argument.
    :param callable tuple_factory: A callable to produce tuples from.  For
        example, to produce lists instead of tuples.
    :param bool retain_collection_types: Do not convert to ``list``
        or ``dict`` when encountering an attribute which type is
        ``tuple``, ``dict`` or ``set``.  Only meaningful if ``recurse`` is
        ``True``.

    :rtype: return type of *tuple_factory*

    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
        class.

    ..  versionadded:: 16.2.0
    """
    attrs = fields(inst.__class__)
    rv = []
    retain = retain_collection_types  # Very long. :/
    for a in attrs:
        v = getattr(inst, a.name)
        if filter is not None and not filter(a, v):
            continue
        if recurse is True:
            if has(v.__class__):
                rv.append(
                    astuple(
                        v,
                        recurse=True,
                        filter=filter,
                        tuple_factory=tuple_factory,
                        retain_collection_types=retain,
                    )
                )
            elif isinstance(v, (tuple, list, set)):
                cf = v.__class__ if retain is True else list
                rv.append(
                    cf(
                        [
                            astuple(
                                j,
                                recurse=True,
                                filter=filter,
                                tuple_factory=tuple_factory,
                                retain_collection_types=retain,
                            )
                            if has(j.__class__)
                            else j
                            for j in v
                        ]
                    )
                )
            elif isinstance(v, dict):
                df = v.__class__ if retain is True else dict
                rv.append(
                    df(
                        (
                            astuple(
                                kk,
                                tuple_factory=tuple_factory,
                                retain_collection_types=retain,
                            )
                            if has(kk.__class__)
                            else kk,
                            astuple(
                                vv,
                                tuple_factory=tuple_factory,
                                retain_collection_types=retain,
                            )
                            if has(vv.__class__)
                            else vv,
                        )
                        for kk, vv in iteritems(v)
                    )
                )
            else:
                rv.append(v)
        else:
            rv.append(v)
    return rv if tuple_factory is list else tuple_factory(rv)


def has(cls):
    """
    Check whether *cls* is a class with ``attrs`` attributes.

    :param type cls: Class to introspect.
    :raise TypeError: If *cls* is not a class.

    :rtype: :class:`bool`
    """
    return getattr(cls, "__attrs_attrs__", None) is not None


def assoc(inst, **changes):
    """
    Copy *inst* and apply *changes*.

    :param inst: Instance of a class with ``attrs`` attributes.
    :param changes: Keyword changes in the new copy.

    :return: A copy of inst with *changes* incorporated.

    :raise attr.exceptions.AttrsAttributeNotFoundError: If *attr_name* couldn't
        be found on *cls*.
    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
        class.

    ..  deprecated:: 17.1.0
        Use :func:`evolve` instead.
    """
    import warnings

    warnings.warn(
        "assoc is deprecated and will be removed after 2018/01.",
        DeprecationWarning,
        stacklevel=2,
    )
    new = copy.copy(inst)
    attrs = fields(inst.__class__)
    for k, v in iteritems(changes):
        a = getattr(attrs, k, NOTHING)
        if a is NOTHING:
            raise AttrsAttributeNotFoundError(
                "{k} is not an attrs attribute on {cl}.".format(
                    k=k, cl=new.__class__
                )
            )
        _obj_setattr(new, k, v)
    return new


def evolve(inst, **changes):
    """
    Create a new instance, based on *inst* with *changes* applied.

    :param inst: Instance of a class with ``attrs`` attributes.
    :param changes: Keyword changes in the new copy.

    :return: A copy of inst with *changes* incorporated.

    :raise TypeError: If *attr_name* couldn't be found in the class
        ``__init__``.
    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
        class.

    ..  versionadded:: 17.1.0
    """
    cls = inst.__class__
    attrs = fields(cls)
    for a in attrs:
        if not a.init:
            continue
        attr_name = a.name  # To deal with private attributes.
        init_name = attr_name if attr_name[0] != "_" else attr_name[1:]
        if init_name not in changes:
            changes[init_name] = getattr(inst, attr_name)
    return cls(**changes)