view mercurial/thirdparty/attr/_next_gen.py @ 50599:921a72735482

safehasattr: pass attribute name as string instead of bytes

This is a step toward replacing `util.safehasattr` usage with plain `hasattr`.
The builtin function behave poorly in Python2 but this was fixed in Python3.

These change are done one by one as they tend to have a small odd to trigger
puzzling breackage.

# SPDX-License-Identifier: MIT

"""
These are Python 3.6+-only and keyword-only APIs that call `attr.s` and
`attr.ib` with different default values.
"""


from functools import partial

from . import setters
from ._funcs import asdict as _asdict
from ._funcs import astuple as _astuple
from ._make import (
    NOTHING,
    _frozen_setattrs,
    _ng_default_on_setattr,
    attrib,
    attrs,
)
from .exceptions import UnannotatedAttributeError


def define(
    maybe_cls=None,
    *,
    these=None,
    repr=None,
    hash=None,
    init=None,
    slots=True,
    frozen=False,
    weakref_slot=True,
    str=False,
    auto_attribs=None,
    kw_only=False,
    cache_hash=False,
    auto_exc=True,
    eq=None,
    order=False,
    auto_detect=True,
    getstate_setstate=None,
    on_setattr=None,
    field_transformer=None,
    match_args=True,
):
    r"""
    Define an ``attrs`` class.

    Differences to the classic `attr.s` that it uses underneath:

    - Automatically detect whether or not *auto_attribs* should be `True` (c.f.
      *auto_attribs* parameter).
    - If *frozen* is `False`, run converters and validators when setting an
      attribute by default.
    - *slots=True*

      .. caution::

         Usually this has only upsides and few visible effects in everyday
         programming. But it *can* lead to some suprising behaviors, so please
         make sure to read :term:`slotted classes`.
    - *auto_exc=True*
    - *auto_detect=True*
    - *order=False*
    - Some options that were only relevant on Python 2 or were kept around for
      backwards-compatibility have been removed.

    Please note that these are all defaults and you can change them as you
    wish.

    :param Optional[bool] auto_attribs: If set to `True` or `False`, it behaves
       exactly like `attr.s`. If left `None`, `attr.s` will try to guess:

       1. If any attributes are annotated and no unannotated `attrs.fields`\ s
          are found, it assumes *auto_attribs=True*.
       2. Otherwise it assumes *auto_attribs=False* and tries to collect
          `attrs.fields`\ s.

    For now, please refer to `attr.s` for the rest of the parameters.

    .. versionadded:: 20.1.0
    .. versionchanged:: 21.3.0 Converters are also run ``on_setattr``.
    """

    def do_it(cls, auto_attribs):
        return attrs(
            maybe_cls=cls,
            these=these,
            repr=repr,
            hash=hash,
            init=init,
            slots=slots,
            frozen=frozen,
            weakref_slot=weakref_slot,
            str=str,
            auto_attribs=auto_attribs,
            kw_only=kw_only,
            cache_hash=cache_hash,
            auto_exc=auto_exc,
            eq=eq,
            order=order,
            auto_detect=auto_detect,
            collect_by_mro=True,
            getstate_setstate=getstate_setstate,
            on_setattr=on_setattr,
            field_transformer=field_transformer,
            match_args=match_args,
        )

    def wrap(cls):
        """
        Making this a wrapper ensures this code runs during class creation.

        We also ensure that frozen-ness of classes is inherited.
        """
        nonlocal frozen, on_setattr

        had_on_setattr = on_setattr not in (None, setters.NO_OP)

        # By default, mutable classes convert & validate on setattr.
        if frozen is False and on_setattr is None:
            on_setattr = _ng_default_on_setattr

        # However, if we subclass a frozen class, we inherit the immutability
        # and disable on_setattr.
        for base_cls in cls.__bases__:
            if base_cls.__setattr__ is _frozen_setattrs:
                if had_on_setattr:
                    raise ValueError(
                        "Frozen classes can't use on_setattr "
                        "(frozen-ness was inherited)."
                    )

                on_setattr = setters.NO_OP
                break

        if auto_attribs is not None:
            return do_it(cls, auto_attribs)

        try:
            return do_it(cls, True)
        except UnannotatedAttributeError:
            return do_it(cls, False)

    # maybe_cls's type depends on the usage of the decorator.  It's a class
    # if it's used as `@attrs` but ``None`` if used as `@attrs()`.
    if maybe_cls is None:
        return wrap
    else:
        return wrap(maybe_cls)


mutable = define
frozen = partial(define, frozen=True, on_setattr=None)


def field(
    *,
    default=NOTHING,
    validator=None,
    repr=True,
    hash=None,
    init=True,
    metadata=None,
    converter=None,
    factory=None,
    kw_only=False,
    eq=None,
    order=None,
    on_setattr=None,
):
    """
    Identical to `attr.ib`, except keyword-only and with some arguments
    removed.

    .. versionadded:: 20.1.0
    """
    return attrib(
        default=default,
        validator=validator,
        repr=repr,
        hash=hash,
        init=init,
        metadata=metadata,
        converter=converter,
        factory=factory,
        kw_only=kw_only,
        eq=eq,
        order=order,
        on_setattr=on_setattr,
    )


def asdict(inst, *, recurse=True, filter=None, value_serializer=None):
    """
    Same as `attr.asdict`, except that collections types are always retained
    and dict is always used as *dict_factory*.

    .. versionadded:: 21.3.0
    """
    return _asdict(
        inst=inst,
        recurse=recurse,
        filter=filter,
        value_serializer=value_serializer,
        retain_collection_types=True,
    )


def astuple(inst, *, recurse=True, filter=None):
    """
    Same as `attr.astuple`, except that collections types are always retained
    and `tuple` is always used as the *tuple_factory*.

    .. versionadded:: 21.3.0
    """
    return _astuple(
        inst=inst, recurse=recurse, filter=filter, retain_collection_types=True
    )