_make.py

# SPDX-License-Identifier: MIT

from __future__ import annotations

import contextlib
import copy
import enum
import functools
import inspect
import itertools
import linecache
import sys
import types
import typing

from operator import itemgetter

# We need to import _compat itself in addition to the _compat members to avoid
# having the thread-local in the globals here.
from . import _compat, _config, setters
from ._compat import (
    PY_3_8_PLUS,
    PY_3_10_PLUS,
    _AnnotationExtractor,
    get_generic_base,
)
from .exceptions import (
    DefaultAlreadySetError,
    FrozenInstanceError,
    NotAnAttrsClassError,
    UnannotatedAttributeError,
)


# This is used at least twice, so cache it here.
_OBJ_SETATTR = object.__setattr__
_INIT_FACTORY_PAT = "__attr_factory_%s"
_CLASSVAR_PREFIXES = (
    "typing.ClassVar",
    "t.ClassVar",
    "ClassVar",
    "typing_extensions.ClassVar",
)
# we don't use a double-underscore prefix because that triggers
# name mangling when trying to create a slot for the field
# (when slots=True)
_HASH_CACHE_FIELD = "_attrs_cached_hash"

_EMPTY_METADATA_SINGLETON = types.MappingProxyType({})

# Unique object for unequivocal getattr() defaults.
_SENTINEL = object()

_DEFAULT_ON_SETATTR = setters.pipe(setters.convert, setters.validate)


class _Nothing(enum.Enum):
    """
    Sentinel to indicate the lack of a value when `None` is ambiguous.

    If extending attrs, you can use ``typing.Literal[NOTHING]`` to show
    that a value may be ``NOTHING``.

    .. versionchanged:: 21.1.0 ``bool(NOTHING)`` is now False.
    .. versionchanged:: 22.2.0 ``NOTHING`` is now an ``enum.Enum`` variant.
    """

    NOTHING = enum.auto()

    def __repr__(self):
        return "NOTHING"

    def __bool__(self):
        return False


NOTHING = _Nothing.NOTHING
"""
Sentinel to indicate the lack of a value when `None` is ambiguous.
"""


class _CacheHashWrapper(int):
    """
    An integer subclass that pickles / copies as None

    This is used for non-slots classes with ``cache_hash=True``, to avoid
    serializing a potentially (even likely) invalid hash value. Since `None`
    is the default value for uncalculated hashes, whenever this is copied,
    the copy's value for the hash should automatically reset.

    See GH #613 for more details.
    """

    def __reduce__(self, _none_constructor=type(None), _args=()):  # noqa: B008
        return _none_constructor, _args


def attrib(
    default=NOTHING,
    validator=None,
    repr=True,
    cmp=None,
    hash=None,
    init=True,
    metadata=None,
    type=None,
    converter=None,
    factory=None,
    kw_only=False,
    eq=None,
    order=None,
    on_setattr=None,
    alias=None,
):
    """
    Create a new attribute on a class.

    ..  warning::

        Does *not* do anything unless the class is also decorated with `attr.s`
        / `attrs.define` / and so on!

    Please consider using `attrs.field` in new code (``attr.ib`` will *never*
    go away, though).

    Args:
        default:
            A value that is used if an *attrs*-generated ``__init__`` is used
            and no value is passed while instantiating or the attribute is
            excluded using ``init=False``.

            If the value is an instance of `attrs.Factory`, its callable will
            be used to construct a new value (useful for mutable data types
            like lists or dicts).

            If a default is not set (or set manually to `attrs.NOTHING`), a
            value *must* be supplied when instantiating; otherwise a
            `TypeError` will be raised.

            The default can also be set using decorator notation as shown
            below.

            .. seealso:: `defaults`

        factory (~typing.Callable):
            Syntactic sugar for ``default=attr.Factory(factory)``.

        validator (~typing.Callable | list[~typing.Callable]):
            Callable that is called by *attrs*-generated ``__init__`` methods
            after the instance has been initialized.  They receive the
            initialized instance, the :func:`~attrs.Attribute`, and the passed
            value.

            The return value is *not* inspected so the validator has to throw
            an exception itself.

            If a `list` is passed, its items are treated as validators and must
            all pass.

            Validators can be globally disabled and re-enabled using
            `attrs.validators.get_disabled` / `attrs.validators.set_disabled`.

            The validator can also be set using decorator notation as shown
            below.

            .. seealso:: :ref:`validators`

        repr (bool | ~typing.Callable):
            Include this attribute in the generated ``__repr__`` method. If
            `True`, include the attribute; if `False`, omit it. By default, the
            built-in ``repr()`` function is used. To override how the attribute
            value is formatted, pass a ``callable`` that takes a single value
            and returns a string. Note that the resulting string is used as-is,
            which means it will be used directly *instead* of calling
            ``repr()`` (the default).

        eq (bool | ~typing.Callable):
            If `True` (default), include this attribute in the generated
            ``__eq__`` and ``__ne__`` methods that check two instances for
            equality. To override how the attribute value is compared, pass a
            callable that takes a single value and returns the value to be
            compared.

            .. seealso:: `comparison`

        order (bool | ~typing.Callable):
            If `True` (default), include this attributes in the generated
            ``__lt__``, ``__le__``, ``__gt__`` and ``__ge__`` methods. To
            override how the attribute value is ordered, pass a callable that
            takes a single value and returns the value to be ordered.

            .. seealso:: `comparison`

        cmp(bool | ~typing.Callable):
            Setting *cmp* is equivalent to setting *eq* and *order* to the same
            value. Must not be mixed with *eq* or *order*.

            .. seealso:: `comparison`

        hash (bool | None):
            Include this attribute in the generated ``__hash__`` method.  If
            `None` (default), mirror *eq*'s value.  This is the correct
            behavior according the Python spec.  Setting this value to anything
            else than `None` is *discouraged*.

            .. seealso:: `hashing`

        init (bool):
            Include this attribute in the generated ``__init__`` method.  It is
            possible to set this to `False` and set a default value. In that
            case this attributed is unconditionally initialized with the
            specified default value or factory.

            .. seealso:: `init`

        converter (typing.Callable | Converter):
            `callable` that is called by *attrs*-generated ``__init__`` methods
            to convert attribute's value to the desired format.

            If a vanilla callable is passed, it is given the passed-in value as
            the only positional argument. It is possible to receive additional
            arguments by wrapping the callable in a `Converter`.

            Either way, the returned value will be used as the new value of the
            attribute.  The value is converted before being passed to the
            validator, if any.

            .. seealso:: :ref:`converters`

        metadata (dict | None):
            An arbitrary mapping, to be used by third-party components.

            .. seealso:: `extending-metadata`.

        type (type):
            The type of the attribute. Nowadays, the preferred method to
            specify the type is using a variable annotation (see :pep:`526`).
            This argument is provided for backwards-compatibility and for usage
            with `make_class`. Regardless of the approach used, the type will
            be stored on ``Attribute.type``.

            Please note that *attrs* doesn't do anything with this metadata by
            itself. You can use it as part of your own code or for `static type
            checking <types>`.

        kw_only (bool):
            Make this attribute keyword-only in the generated ``__init__`` (if
            ``init`` is `False`, this parameter is ignored).

        on_setattr (~typing.Callable | list[~typing.Callable] | None | typing.Literal[attrs.setters.NO_OP]):
            Allows to overwrite the *on_setattr* setting from `attr.s`. If left
            `None`, the *on_setattr* value from `attr.s` is used. Set to
            `attrs.setters.NO_OP` to run **no** `setattr` hooks for this
            attribute -- regardless of the setting in `attr.s`.

        alias (str | None):
            Override this attribute's parameter name in the generated
            ``__init__`` method. If left `None`, default to ``name`` stripped
            of leading underscores. See `private-attributes`.

    .. versionadded:: 15.2.0 *convert*
    .. versionadded:: 16.3.0 *metadata*
    .. versionchanged:: 17.1.0 *validator* can be a ``list`` now.
    .. versionchanged:: 17.1.0
       *hash* is `None` and therefore mirrors *eq* by default.
    .. versionadded:: 17.3.0 *type*
    .. deprecated:: 17.4.0 *convert*
    .. versionadded:: 17.4.0
       *converter* as a replacement for the deprecated *convert* to achieve
       consistency with other noun-based arguments.
    .. versionadded:: 18.1.0
       ``factory=f`` is syntactic sugar for ``default=attr.Factory(f)``.
    .. versionadded:: 18.2.0 *kw_only*
    .. versionchanged:: 19.2.0 *convert* keyword argument removed.
    .. versionchanged:: 19.2.0 *repr* also accepts a custom callable.
    .. deprecated:: 19.2.0 *cmp* Removal on or after 2021-06-01.
    .. versionadded:: 19.2.0 *eq* and *order*
    .. versionadded:: 20.1.0 *on_setattr*
    .. versionchanged:: 20.3.0 *kw_only* backported to Python 2
    .. versionchanged:: 21.1.0
       *eq*, *order*, and *cmp* also accept a custom callable
    .. versionchanged:: 21.1.0 *cmp* undeprecated
    .. versionadded:: 22.2.0 *alias*
    """
    eq, eq_key, order, order_key = _determine_attrib_eq_order(
        cmp, eq, order, True
    )

    if hash is not None and hash is not True and hash is not False:
        msg = "Invalid value for hash.  Must be True, False, or None."
        raise TypeError(msg)

    if factory is not None:
        if default is not NOTHING:
            msg = (
                "The `default` and `factory` arguments are mutually exclusive."
            )
            raise ValueError(msg)
        if not callable(factory):
            msg = "The `factory` argument must be a callable."
            raise ValueError(msg)
        default = Factory(factory)

    if metadata is None:
        metadata = {}

    # Apply syntactic sugar by auto-wrapping.
    if isinstance(on_setattr, (list, tuple)):
        on_setattr = setters.pipe(*on_setattr)

    if validator and isinstance(validator, (list, tuple)):
        validator = and_(*validator)

    if converter and isinstance(converter, (list, tuple)):
        converter = pipe(*converter)

    return _CountingAttr(
        default=default,
        validator=validator,
        repr=repr,
        cmp=None,
        hash=hash,
        init=init,
        converter=converter,
        metadata=metadata,
        type=type,
        kw_only=kw_only,
        eq=eq,
        eq_key=eq_key,
        order=order,
        order_key=order_key,
        on_setattr=on_setattr,
        alias=alias,
    )


def _compile_and_eval(script, globs, locs=None, filename=""):
    """
    Evaluate the script with the given global (globs) and local (locs)
    variables.
    """
    bytecode = compile(script, filename, "exec")
    eval(bytecode, globs, locs)


def _make_method(name, script, filename, globs, locals=None):
    """
    Create the method with the script given and return the method object.
    """
    locs = {} if locals is None else locals

    # In order of debuggers like PDB being able to step through the code,
    # we add a fake linecache entry.
    count = 1
    base_filename = filename
    while True:
        linecache_tuple = (
            len(script),
            None,
            script.splitlines(True),
            filename,
        )
        old_val = linecache.cache.setdefault(filename, linecache_tuple)
        if old_val == linecache_tuple:
            break

        filename = f"{base_filename[:-1]}-{count}>"
        count += 1

    _compile_and_eval(script, globs, locs, filename)

    return locs[name]


def _make_attr_tuple_class(cls_name, attr_names):
    """
    Create a tuple subclass to hold `Attribute`s for an `attrs` class.

    The subclass is a bare tuple with properties for names.

    class MyClassAttributes(tuple):
        __slots__ = ()
        x = property(itemgetter(0))
    """
    attr_class_name = f"{cls_name}Attributes"
    attr_class_template = [
        f"class {attr_class_name}(tuple):",
        "    __slots__ = ()",
    ]
    if attr_names:
        for i, attr_name in enumerate(attr_names):
            attr_class_template.append(
                f"    {attr_name} = _attrs_property(_attrs_itemgetter({i}))"
            )
    else:
        attr_class_template.append("    pass")
    globs = {"_attrs_itemgetter": itemgetter, "_attrs_property": property}
    _compile_and_eval("\n".join(attr_class_template), globs)
    return globs[attr_class_name]


# Tuple class for extracted attributes from a class definition.
# `base_attrs` is a subset of `attrs`.
_Attributes = _make_attr_tuple_class(
    "_Attributes",
    [
        # all attributes to build dunder methods for
        "attrs",
        # attributes that have been inherited
        "base_attrs",
        # map inherited attributes to their originating classes
        "base_attrs_map",
    ],
)


def _is_class_var(annot):
    """
    Check whether *annot* is a typing.ClassVar.

    The string comparison hack is used to avoid evaluating all string
    annotations which would put attrs-based classes at a performance
    disadvantage compared to plain old classes.
    """
    annot = str(annot)

    # Annotation can be quoted.
    if annot.startswith(("'", '"')) and annot.endswith(("'", '"')):
        annot = annot[1:-1]

    return annot.startswith(_CLASSVAR_PREFIXES)


def _has_own_attribute(cls, attrib_name):
    """
    Check whether *cls* defines *attrib_name* (and doesn't just inherit it).
    """
    attr = getattr(cls, attrib_name, _SENTINEL)
    if attr is _SENTINEL:
        return False

    for base_cls in cls.__mro__[1:]:
        a = getattr(base_cls, attrib_name, None)
        if attr is a:
            return False

    return True


def _get_annotations(cls):
    """
    Get annotations for *cls*.
    """
    if _has_own_attribute(cls, "__annotations__"):
        return cls.__annotations__

    return {}


def _collect_base_attrs(cls, taken_attr_names):
    """
    Collect attr.ibs from base classes of *cls*, except *taken_attr_names*.
    """
    base_attrs = []
    base_attr_map = {}  # A dictionary of base attrs to their classes.

    # Traverse the MRO and collect attributes.
    for base_cls in reversed(cls.__mro__[1:-1]):
        for a in getattr(base_cls, "__attrs_attrs__", []):
            if a.inherited or a.name in taken_attr_names:
                continue

            a = a.evolve(inherited=True)  # noqa: PLW2901
            base_attrs.append(a)
            base_attr_map[a.name] = base_cls

    # For each name, only keep the freshest definition i.e. the furthest at the
    # back.  base_attr_map is fine because it gets overwritten with every new
    # instance.
    filtered = []
    seen = set()
    for a in reversed(base_attrs):
        if a.name in seen:
            continue
        filtered.insert(0, a)
        seen.add(a.name)

    return filtered, base_attr_map


def _collect_base_attrs_broken(cls, taken_attr_names):
    """
    Collect attr.ibs from base classes of *cls*, except *taken_attr_names*.

    N.B. *taken_attr_names* will be mutated.

    Adhere to the old incorrect behavior.

    Notably it collects from the front and considers inherited attributes which
    leads to the buggy behavior reported in #428.
    """
    base_attrs = []
    base_attr_map = {}  # A dictionary of base attrs to their classes.

    # Traverse the MRO and collect attributes.
    for base_cls in cls.__mro__[1:-1]:
        for a in getattr(base_cls, "__attrs_attrs__", []):
            if a.name in taken_attr_names:
                continue

            a = a.evolve(inherited=True)  # noqa: PLW2901
            taken_attr_names.add(a.name)
            base_attrs.append(a)
            base_attr_map[a.name] = base_cls

    return base_attrs, base_attr_map


def _transform_attrs(
    cls, these, auto_attribs, kw_only, collect_by_mro, field_transformer
):
    """
    Transform all `_CountingAttr`s on a class into `Attribute`s.

    If *these* is passed, use that and don't look for them on the class.

    If *collect_by_mro* is True, collect them in the correct MRO order,
    otherwise use the old -- incorrect -- order.  See #428.

    Return an `_Attributes`.
    """
    cd = cls.__dict__
    anns = _get_annotations(cls)

    if these is not None:
        ca_list = list(these.items())
    elif auto_attribs is True:
        ca_names = {
            name
            for name, attr in cd.items()
            if isinstance(attr, _CountingAttr)
        }
        ca_list = []
        annot_names = set()
        for attr_name, type in anns.items():
            if _is_class_var(type):
                continue
            annot_names.add(attr_name)
            a = cd.get(attr_name, NOTHING)

            if not isinstance(a, _CountingAttr):
                a = attrib() if a is NOTHING else attrib(default=a)
            ca_list.append((attr_name, a))

        unannotated = ca_names - annot_names
        if len(unannotated) > 0:
            raise UnannotatedAttributeError(
                "The following `attr.ib`s lack a type annotation: "
                + ", ".join(
                    sorted(unannotated, key=lambda n: cd.get(n).counter)
                )
                + "."
            )
    else:
        ca_list = sorted(
            (
                (name, attr)
                for name, attr in cd.items()
                if isinstance(attr, _CountingAttr)
            ),
            key=lambda e: e[1].counter,
        )

    own_attrs = [
        Attribute.from_counting_attr(
            name=attr_name, ca=ca, type=anns.get(attr_name)
        )
        for attr_name, ca in ca_list
    ]

    if collect_by_mro:
        base_attrs, base_attr_map = _collect_base_attrs(
            cls, {a.name for a in own_attrs}
        )
    else:
        base_attrs, base_attr_map = _collect_base_attrs_broken(
            cls, {a.name for a in own_attrs}
        )

    if kw_only:
        own_attrs = [a.evolve(kw_only=True) for a in own_attrs]
        base_attrs = [a.evolve(kw_only=True) for a in base_attrs]

    attrs = base_attrs + own_attrs

    # Mandatory vs non-mandatory attr order only matters when they are part of
    # the __init__ signature and when they aren't kw_only (which are moved to
    # the end and can be mandatory or non-mandatory in any order, as they will
    # be specified as keyword args anyway). Check the order of those attrs:
    had_default = False
    for a in (a for a in attrs if a.init is not False and a.kw_only is False):
        if had_default is True and a.default is NOTHING:
            msg = f"No mandatory attributes allowed after an attribute with a default value or factory.  Attribute in question: {a!r}"
            raise ValueError(msg)

        if had_default is False and a.default is not NOTHING:
            had_default = True

    if field_transformer is not None:
        attrs = field_transformer(cls, attrs)

    # Resolve default field alias after executing field_transformer.
    # This allows field_transformer to differentiate between explicit vs
    # default aliases and supply their own defaults.
    attrs = [
        a.evolve(alias=_default_init_alias_for(a.name)) if not a.alias else a
        for a in attrs
    ]

    # Create AttrsClass *after* applying the field_transformer since it may
    # add or remove attributes!
    attr_names = [a.name for a in attrs]
    AttrsClass = _make_attr_tuple_class(cls.__name__, attr_names)

    return _Attributes((AttrsClass(attrs), base_attrs, base_attr_map))


def _make_cached_property_getattr(cached_properties, original_getattr, cls):
    lines = [
        # Wrapped to get `__class__` into closure cell for super()
        # (It will be replaced with the newly constructed class after construction).
        "def wrapper(_cls):",
        "    __class__ = _cls",
        "    def __getattr__(self, item, cached_properties=cached_properties, original_getattr=original_getattr, _cached_setattr_get=_cached_setattr_get):",
        "         func = cached_properties.get(item)",
        "         if func is not None:",
        "              result = func(self)",
        "              _setter = _cached_setattr_get(self)",
        "              _setter(item, result)",
        "              return result",
    ]
    if original_getattr is not None:
        lines.append(
            "         return original_getattr(self, item)",
        )
    else:
        lines.extend(
            [
                "         try:",
                "             return super().__getattribute__(item)",
                "         except AttributeError:",
                "             if not hasattr(super(), '__getattr__'):",
                "                 raise",
                "             return super().__getattr__(item)",
                "         original_error = f\"'{self.__class__.__name__}' object has no attribute '{item}'\"",
                "         raise AttributeError(original_error)",
            ]
        )

    lines.extend(
        [
            "    return __getattr__",
            "__getattr__ = wrapper(_cls)",
        ]
    )

    unique_filename = _generate_unique_filename(cls, "getattr")

    glob = {
        "cached_properties": cached_properties,
        "_cached_setattr_get": _OBJ_SETATTR.__get__,
        "original_getattr": original_getattr,
    }

    return _make_method(
        "__getattr__",
        "\n".join(lines),
        unique_filename,
        glob,
        locals={
            "_cls": cls,
        },
    )


def _frozen_setattrs(self, name, value):
    """
    Attached to frozen classes as __setattr__.
    """
    if isinstance(self, BaseException) and name in (
        "__cause__",
        "__context__",
        "__traceback__",
    ):
        BaseException.__setattr__(self, name, value)
        return

    raise FrozenInstanceError()


def _frozen_delattrs(self, name):
    """
    Attached to frozen classes as __delattr__.
    """
    raise FrozenInstanceError()


class _ClassBuilder:
    """
    Iteratively build *one* class.
    """

    __slots__ = (
        "_attr_names",
        "_attrs",
        "_base_attr_map",
        "_base_names",
        "_cache_hash",
        "_cls",
        "_cls_dict",
        "_delete_attribs",
        "_frozen",
        "_has_pre_init",
        "_pre_init_has_args",
        "_has_post_init",
        "_is_exc",
        "_on_setattr",
        "_slots",
        "_weakref_slot",
        "_wrote_own_setattr",
        "_has_custom_setattr",
    )

    def __init__(
        self,
        cls,
        these,
        slots,
        frozen,
        weakref_slot,
        getstate_setstate,
        auto_attribs,
        kw_only,
        cache_hash,
        is_exc,
        collect_by_mro,
        on_setattr,
        has_custom_setattr,
        field_transformer,
    ):
        attrs, base_attrs, base_map = _transform_attrs(
            cls,
            these,
            auto_attribs,
            kw_only,
            collect_by_mro,
            field_transformer,
        )

        self._cls = cls
        self._cls_dict = dict(cls.__dict__) if slots else {}
        self._attrs = attrs
        self._base_names = {a.name for a in base_attrs}
        self._base_attr_map = base_map
        self._attr_names = tuple(a.name for a in attrs)
        self._slots = slots
        self._frozen = frozen
        self._weakref_slot = weakref_slot
        self._cache_hash = cache_hash
        self._has_pre_init = bool(getattr(cls, "__attrs_pre_init__", False))
        self._pre_init_has_args = False
        if self._has_pre_init:
            # Check if the pre init method has more arguments than just `self`
            # We want to pass arguments if pre init expects arguments
            pre_init_func = cls.__attrs_pre_init__
            pre_init_signature = inspect.signature(pre_init_func)
            self._pre_init_has_args = len(pre_init_signature.parameters) > 1
        self._has_post_init = bool(getattr(cls, "__attrs_post_init__", False))
        self._delete_attribs = not bool(these)
        self._is_exc = is_exc
        self._on_setattr = on_setattr

        self._has_custom_setattr = has_custom_setattr
        self._wrote_own_setattr = False

        self._cls_dict["__attrs_attrs__"] = self._attrs

        if frozen:
            self._cls_dict["__setattr__"] = _frozen_setattrs
            self._cls_dict["__delattr__"] = _frozen_delattrs

            self._wrote_own_setattr = True
        elif on_setattr in (
            _DEFAULT_ON_SETATTR,
            setters.validate,
            setters.convert,
        ):
            has_validator = has_converter = False
            for a in attrs:
                if a.validator is not None:
                    has_validator = True
                if a.converter is not None:
                    has_converter = True

                if has_validator and has_converter:
                    break
            if (
                (
                    on_setattr == _DEFAULT_ON_SETATTR
                    and not (has_validator or has_converter)
                )
                or (on_setattr == setters.validate and not has_validator)
                or (on_setattr == setters.convert and not has_converter)
            ):
                # If class-level on_setattr is set to convert + validate, but
                # there's no field to convert or validate, pretend like there's
                # no on_setattr.
                self._on_setattr = None

        if getstate_setstate:
            (
                self._cls_dict["__getstate__"],
                self._cls_dict["__setstate__"],
            ) = self._make_getstate_setstate()

    def __repr__(self):
        return f"<_ClassBuilder(cls={self._cls.__name__})>"

    if PY_3_10_PLUS:
        import abc

        def build_class(self):
            """
            Finalize class based on the accumulated configuration.

            Builder cannot be used after calling this method.
            """
            if self._slots is True:
                return self._create_slots_class()

            return self.abc.update_abstractmethods(
                self._patch_original_class()
            )

    else:

        def build_class(self):
            """
            Finalize class based on the accumulated configuration.

            Builder cannot be used after calling this method.
            """
            if self._slots is True:
                return self._create_slots_class()

            return self._patch_original_class()

    def _patch_original_class(self):
        """
        Apply accumulated methods and return the class.
        """
        cls = self._cls
        base_names = self._base_names

        # Clean class of attribute definitions (`attr.ib()`s).
        if self._delete_attribs:
            for name in self._attr_names:
                if (
                    name not in base_names
                    and getattr(cls, name, _SENTINEL) is not _SENTINEL
                ):
                    # An AttributeError can happen if a base class defines a
                    # class variable and we want to set an attribute with the
                    # same name by using only a type annotation.
                    with contextlib.suppress(AttributeError):
                        delattr(cls, name)

        # Attach our dunder methods.
        for name, value in self._cls_dict.items():
            setattr(cls, name, value)

        # If we've inherited an attrs __setattr__ and don't write our own,
        # reset it to object's.
        if not self._wrote_own_setattr and getattr(
            cls, "__attrs_own_setattr__", False
        ):
            cls.__attrs_own_setattr__ = False

            if not self._has_custom_setattr:
                cls.__setattr__ = _OBJ_SETATTR

        return cls

    def _create_slots_class(self):
        """
        Build and return a new class with a `__slots__` attribute.
        """
        cd = {
            k: v
            for k, v in self._cls_dict.items()
            if k not in (*tuple(self._attr_names), "__dict__", "__weakref__")
        }

        # If our class doesn't have its own implementation of __setattr__
        # (either from the user or by us), check the bases, if one of them has
        # an attrs-made __setattr__, that needs to be reset. We don't walk the
        # MRO because we only care about our immediate base classes.
        # XXX: This can be confused by subclassing a slotted attrs class with
        # XXX: a non-attrs class and subclass the resulting class with an attrs
        # XXX: class.  See `test_slotted_confused` for details.  For now that's
        # XXX: OK with us.
        if not self._wrote_own_setattr:
            cd["__attrs_own_setattr__"] = False

            if not self._has_custom_setattr:
                for base_cls in self._cls.__bases__:
                    if base_cls.__dict__.get("__attrs_own_setattr__", False):
                        cd["__setattr__"] = _OBJ_SETATTR
                        break

        # Traverse the MRO to collect existing slots
        # and check for an existing __weakref__.
        existing_slots = {}
        weakref_inherited = False
        for base_cls in self._cls.__mro__[1:-1]:
            if base_cls.__dict__.get("__weakref__", None) is not None:
                weakref_inherited = True
            existing_slots.update(
                {
                    name: getattr(base_cls, name)
                    for name in getattr(base_cls, "__slots__", [])
                }
            )

        base_names = set(self._base_names)

        names = self._attr_names
        if (
            self._weakref_slot
            and "__weakref__" not in getattr(self._cls, "__slots__", ())
            and "__weakref__" not in names
            and not weakref_inherited
        ):
            names += ("__weakref__",)

        if PY_3_8_PLUS:
            cached_properties = {
                name: cached_property.func
                for name, cached_property in cd.items()
                if isinstance(cached_property, functools.cached_property)
            }
        else:
            # `functools.cached_property` was introduced in 3.8.
            # So can't be used before this.
            cached_properties = {}

        # Collect methods with a `__class__` reference that are shadowed in the new class.
        # To know to update them.
        additional_closure_functions_to_update = []
        if cached_properties:
            class_annotations = _get_annotations(self._cls)
            for name, func in cached_properties.items():
                # Add cached properties to names for slotting.
                names += (name,)
                # Clear out function from class to avoid clashing.
                del cd[name]
                additional_closure_functions_to_update.append(func)
                annotation = inspect.signature(func).return_annotation
                if annotation is not inspect.Parameter.empty:
                    class_annotations[name] = annotation

            original_getattr = cd.get("__getattr__")
            if original_getattr is not None:
                additional_closure_functions_to_update.append(original_getattr)

            cd["__getattr__"] = _make_cached_property_getattr(
                cached_properties, original_getattr, self._cls
            )

        # We only add the names of attributes that aren't inherited.
        # Setting __slots__ to inherited attributes wastes memory.
        slot_names = [name for name in names if name not in base_names]

        # There are slots for attributes from current class
        # that are defined in parent classes.
        # As their descriptors may be overridden by a child class,
        # we collect them here and update the class dict
        reused_slots = {
            slot: slot_descriptor
            for slot, slot_descriptor in existing_slots.items()
            if slot in slot_names
        }
        slot_names = [name for name in slot_names if name not in reused_slots]
        cd.update(reused_slots)
        if self._cache_hash:
            slot_names.append(_HASH_CACHE_FIELD)

        cd["__slots__"] = tuple(slot_names)

        cd["__qualname__"] = self._cls.__qualname__

        # Create new class based on old class and our methods.
        cls = type(self._cls)(self._cls.__name__, self._cls.__bases__, cd)

        # The following is a fix for
        # <https://github.com/python-attrs/attrs/issues/102>.
        # If a method mentions `__class__` or uses the no-arg super(), the
        # compiler will bake a reference to the class in the method itself
        # as `method.__closure__`.  Since we replace the class with a
        # clone, we rewrite these references so it keeps working.
        for item in itertools.chain(
            cls.__dict__.values(), additional_closure_functions_to_update
        ):
            if isinstance(item, (classmethod, staticmethod)):
                # Class- and staticmethods hide their functions inside.
                # These might need to be rewritten as well.
                closure_cells = getattr(item.__func__, "__closure__", None)
            elif isinstance(item, property):
                # Workaround for property `super()` shortcut (PY3-only).
                # There is no universal way for other descriptors.
                closure_cells = getattr(item.fget, "__closure__", None)
            else:
                closure_cells = getattr(item, "__closure__", None)

            if not closure_cells:  # Catch None or the empty list.
                continue
            for cell in closure_cells:
                try:
                    match = cell.cell_contents is self._cls
                except ValueError:  # noqa: PERF203
                    # ValueError: Cell is empty
                    pass
                else:
                    if match:
                        cell.cell_contents = cls
        return cls

    def add_repr(self, ns, only_non_default_attr_in_repr=False):
        self._cls_dict["__repr__"] = self._add_method_dunders(
            _make_repr(
                self._attrs,
                ns,
                self._cls,
                only_non_default_attr_in_repr=only_non_default_attr_in_repr,
            )
        )
        return self

    def add_str(self):
        repr = self._cls_dict.get("__repr__")
        if repr is None:
            msg = "__str__ can only be generated if a __repr__ exists."
            raise ValueError(msg)

        def __str__(self):
            return self.__repr__()

        self._cls_dict["__str__"] = self._add_method_dunders(__str__)
        return self

    def _make_getstate_setstate(self):
        """
        Create custom __setstate__ and __getstate__ methods.
        """
        # __weakref__ is not writable.
        state_attr_names = tuple(
            an for an in self._attr_names if an != "__weakref__"
        )

        def slots_getstate(self):
            """
            Automatically created by attrs.
            """
            return {name: getattr(self, name) for name in state_attr_names}

        hash_caching_enabled = self._cache_hash

        def slots_setstate(self, state):
            """
            Automatically created by attrs.
            """
            __bound_setattr = _OBJ_SETATTR.__get__(self)
            if isinstance(state, tuple):
                # Backward compatibility with attrs instances pickled with
                # attrs versions before v22.2.0 which stored tuples.
                for name, value in zip(state_attr_names, state):
                    __bound_setattr(name, value)
            else:
                for name in state_attr_names:
                    if name in state:
                        __bound_setattr(name, state[name])

            # The hash code cache is not included when the object is
            # serialized, but it still needs to be initialized to None to
            # indicate that the first call to __hash__ should be a cache
            # miss.
            if hash_caching_enabled:
                __bound_setattr(_HASH_CACHE_FIELD, None)

        return slots_getstate, slots_setstate

    def make_unhashable(self):
        self._cls_dict["__hash__"] = None
        return self

    def add_hash(self):
        self._cls_dict["__hash__"] = self._add_method_dunders(
            _make_hash(
                self._cls,
                self._attrs,
                frozen=self._frozen,
                cache_hash=self._cache_hash,
            )
        )

        return self

    def add_init(self):
        self._cls_dict["__init__"] = self._add_method_dunders(
            _make_init(
                self._cls,
                self._attrs,
                self._has_pre_init,
                self._pre_init_has_args,
                self._has_post_init,
                self._frozen,
                self._slots,
                self._cache_hash,
                self._base_attr_map,
                self._is_exc,
                self._on_setattr,
                attrs_init=False,
            )
        )

        return self

    def add_match_args(self):
        self._cls_dict["__match_args__"] = tuple(
            field.name
            for field in self._attrs
            if field.init and not field.kw_only
        )

    def add_attrs_init(self):
        self._cls_dict["__attrs_init__"] = self._add_method_dunders(
            _make_init(
                self._cls,
                self._attrs,
                self._has_pre_init,
                self._pre_init_has_args,
                self._has_post_init,
                self._frozen,
                self._slots,
                self._cache_hash,
                self._base_attr_map,
                self._is_exc,
                self._on_setattr,
                attrs_init=True,
            )
        )

        return self

    def add_eq(self):
        cd = self._cls_dict

        cd["__eq__"] = self._add_method_dunders(
            _make_eq(self._cls, self._attrs)
        )
        cd["__ne__"] = self._add_method_dunders(_make_ne())

        return self

    def add_order(self):
        cd = self._cls_dict

        cd["__lt__"], cd["__le__"], cd["__gt__"], cd["__ge__"] = (
            self._add_method_dunders(meth)
            for meth in _make_order(self._cls, self._attrs)
        )

        return self

    def add_setattr(self):
        if self._frozen:
            return self

        sa_attrs = {}
        for a in self._attrs:
            on_setattr = a.on_setattr or self._on_setattr
            if on_setattr and on_setattr is not setters.NO_OP:
                sa_attrs[a.name] = a, on_setattr

        if not sa_attrs:
            return self

        if self._has_custom_setattr:
            # We need to write a __setattr__ but there already is one!
            msg = "Can't combine custom __setattr__ with on_setattr hooks."
            raise ValueError(msg)

        # docstring comes from _add_method_dunders
        def __setattr__(self, name, val):
            try:
                a, hook = sa_attrs[name]
            except KeyError:
                nval = val
            else:
                nval = hook(self, a, val)

            _OBJ_SETATTR(self, name, nval)

        self._cls_dict["__attrs_own_setattr__"] = True
        self._cls_dict["__setattr__"] = self._add_method_dunders(__setattr__)
        self._wrote_own_setattr = True

        return self

    def _add_method_dunders(self, method):
        """
        Add __module__ and __qualname__ to a *method* if possible.
        """
        with contextlib.suppress(AttributeError):
            method.__module__ = self._cls.__module__

        with contextlib.suppress(AttributeError):
            method.__qualname__ = f"{self._cls.__qualname__}.{method.__name__}"

        with contextlib.suppress(AttributeError):
            method.__doc__ = (
                "Method generated by attrs for class "
                f"{self._cls.__qualname__}."
            )

        return method


def _determine_attrs_eq_order(cmp, eq, order, default_eq):
    """
    Validate the combination of *cmp*, *eq*, and *order*. Derive the effective
    values of eq and order.  If *eq* is None, set it to *default_eq*.
    """
    if cmp is not None and any((eq is not None, order is not None)):
        msg = "Don't mix `cmp` with `eq' and `order`."
        raise ValueError(msg)

    # cmp takes precedence due to bw-compatibility.
    if cmp is not None:
        return cmp, cmp

    # If left None, equality is set to the specified default and ordering
    # mirrors equality.
    if eq is None:
        eq = default_eq

    if order is None:
        order = eq

    if eq is False and order is True:
        msg = "`order` can only be True if `eq` is True too."
        raise ValueError(msg)

    return eq, order


def _determine_attrib_eq_order(cmp, eq, order, default_eq):
    """
    Validate the combination of *cmp*, *eq*, and *order*. Derive the effective
    values of eq and order.  If *eq* is None, set it to *default_eq*.
    """
    if cmp is not None and any((eq is not None, order is not None)):
        msg = "Don't mix `cmp` with `eq' and `order`."
        raise ValueError(msg)

    def decide_callable_or_boolean(value):
        """
        Decide whether a key function is used.
        """
        if callable(value):
            value, key = True, value
        else:
            key = None
        return value, key

    # cmp takes precedence due to bw-compatibility.
    if cmp is not None:
        cmp, cmp_key = decide_callable_or_boolean(cmp)
        return cmp, cmp_key, cmp, cmp_key

    # If left None, equality is set to the specified default and ordering
    # mirrors equality.
    if eq is None:
        eq, eq_key = default_eq, None
    else:
        eq, eq_key = decide_callable_or_boolean(eq)

    if order is None:
        order, order_key = eq, eq_key
    else:
        order, order_key = decide_callable_or_boolean(order)

    if eq is False and order is True:
        msg = "`order` can only be True if `eq` is True too."
        raise ValueError(msg)

    return eq, eq_key, order, order_key


def _determine_whether_to_implement(
    cls, flag, auto_detect, dunders, default=True
):
    """
    Check whether we should implement a set of methods for *cls*.

    *flag* is the argument passed into @attr.s like 'init', *auto_detect* the
    same as passed into @attr.s and *dunders* is a tuple of attribute names
    whose presence signal that the user has implemented it themselves.

    Return *default* if no reason for either for or against is found.
    """
    if flag is True or flag is False:
        return flag

    if flag is None and auto_detect is False:
        return default

    # Logically, flag is None and auto_detect is True here.
    for dunder in dunders:
        if _has_own_attribute(cls, dunder):
            return False

    return default


def attrs(
    maybe_cls=None,
    these=None,
    repr_ns=None,
    repr=None,
    cmp=None,
    hash=None,
    init=None,
    slots=False,
    frozen=False,
    weakref_slot=True,
    str=False,
    auto_attribs=False,
    kw_only=False,
    cache_hash=False,
    auto_exc=False,
    eq=None,
    order=None,
    auto_detect=False,
    collect_by_mro=False,
    getstate_setstate=None,
    on_setattr=None,
    field_transformer=None,
    match_args=True,
    unsafe_hash=None,
    only_non_default_attr_in_repr=False,
):
    r"""
    A class decorator that adds :term:`dunder methods` according to the
    specified attributes using `attr.ib` or the *these* argument.

    Consider using `attrs.define` / `attrs.frozen` in new code (``attr.s`` will
    *never* go away, though).

    Args:
        these (dict[str, object]):
            A dictionary of name to the (private) return value of `attr.ib`
            mappings. This is useful to avoid the definition of your attributes
            within the class body because you can't (for example, if you want
            to add ``__repr__`` methods to Django models) or don't want to.

            If *these* is not `None`, *attrs* will *not* search the class body
            for attributes and will *not* remove any attributes from it.

            The order is deduced from the order of the attributes inside
            *these*.

        repr_ns (str):
            When using nested classes, there was no way in Python 2 to
            automatically detect that.  This argument allows to set a custom
            name for a more meaningful ``repr`` output.  This argument is
            pointless in Python 3 and is therefore deprecated.

        auto_detect (bool):
            Instead of setting the *init*, *repr*, *eq*, *order*, and *hash*
            arguments explicitly, assume they are set to `True` **unless any**
            of the involved methods for one of the arguments is implemented in
            the *current* class (meaning, it is *not* inherited from some base
            class).

            So, for example by implementing ``__eq__`` on a class yourself,
            *attrs* will deduce ``eq=False`` and will create *neither*
            ``__eq__`` *nor* ``__ne__`` (but Python classes come with a
            sensible ``__ne__`` by default, so it *should* be enough to only
            implement ``__eq__`` in most cases).

            .. warning::

                If you prevent *attrs* from creating the ordering methods for
                you (``order=False``, for example, by implementing ``__le__``),
                it becomes *your* responsibility to make sure its ordering is
                sound. The best way is to use the `functools.total_ordering`
                decorator.

            Passing `True` or `False` to *init*, *repr*, *eq*, *order*, *cmp*,
            or *hash* overrides whatever *auto_detect* would determine.

        repr(bool):
            Create a ``__repr__`` method with a human readable representation
            of *attrs* attributes..

        str (bool):
            Create a ``__str__`` method that is identical to ``__repr__``. This
            is usually not necessary except for `Exception`\ s.

        eq (bool | None):
            If `True` or `None` (default), add ``__eq__`` and ``__ne__``
            methods that check two instances for equality.

            They compare the instances as if they were tuples of their *attrs*
            attributes if and only if the types of both classes are
            *identical*!

            .. seealso:: `comparison`

        order (bool | None):
            If `True`, add ``__lt__``, ``__le__``, ``__gt__``, and ``__ge__``
            methods that behave like *eq* above and allow instances to be
            ordered. If `None` (default) mirror value of *eq*.

            .. seealso:: `comparison`

        cmp (bool | None):
            Setting *cmp* is equivalent to setting *eq* and *order* to the same
            value. Must not be mixed with *eq* or *order*.

            .. seealso:: `comparison`

        unsafe_hash (bool | None):
            If `None` (default), the ``__hash__`` method is generated according
            how *eq* and *frozen* are set.

            1. If *both* are True, *attrs* will generate a ``__hash__`` for
               you.
            2. If *eq* is True and *frozen* is False, ``__hash__`` will be set
               to None, marking it unhashable (which it is).
            3. If *eq* is False, ``__hash__`` will be left untouched meaning
               the ``__hash__`` method of the base class will be used (if base
               class is ``object``, this means it will fall back to id-based
               hashing.).

            Although not recommended, you can decide for yourself and force
            *attrs* to create one (for example, if the class is immutable even
            though you didn't freeze it programmatically) by passing `True` or
            not.  Both of these cases are rather special and should be used
            carefully.

            .. seealso::

                - Our documentation on `hashing`,
                - Python's documentation on `object.__hash__`,
                - and the `GitHub issue that led to the default \ behavior
                  <https://github.com/python-attrs/attrs/issues/136>`_ for more
                  details.

        hash (bool | None):
            Alias for *unsafe_hash*. *unsafe_hash* takes precedence.

        init (bool):
            Create a ``__init__`` method that initializes the *attrs*
            attributes. Leading underscores are stripped for the argument name
            (unless an alias is set on the attribute). If a
            ``__attrs_pre_init__`` method exists on the class, it will be
            called before the class is initialized. If a
            ``__attrs_post_init__`` method exists on the class, it will be
            called after the class is fully initialized.

            If ``init`` is `False`, an ``__attrs_init__`` method will be
            injected instead. This allows you to define a custom ``__init__``
            method that can do pre-init work such as ``super().__init__()``,
            and then call ``__attrs_init__()`` and ``__attrs_post_init__()``.

            .. seealso:: `init`

        slots (bool):
            Create a :term:`slotted class <slotted classes>` that's more
            memory-efficient. Slotted classes are generally superior to the
            default dict classes, but have some gotchas you should know about,
            so we encourage you to read the :term:`glossary entry <slotted
            classes>`.

        frozen (bool):
            Make instances immutable after initialization.  If someone attempts
            to modify a frozen instance, `attrs.exceptions.FrozenInstanceError`
            is raised.

            .. note::

                1. This is achieved by installing a custom ``__setattr__``
                   method on your class, so you can't implement your own.

                2. True immutability is impossible in Python.

                3. This *does* have a minor a runtime performance `impact
                   <how-frozen>` when initializing new instances.  In other
                   words: ``__init__`` is slightly slower with ``frozen=True``.

                4. If a class is frozen, you cannot modify ``self`` in
                   ``__attrs_post_init__`` or a self-written ``__init__``. You
                   can circumvent that limitation by using
                   ``object.__setattr__(self, "attribute_name", value)``.

                5. Subclasses of a frozen class are frozen too.

        weakref_slot (bool):
            Make instances weak-referenceable.  This has no effect unless
            ``slots`` is also enabled.

        auto_attribs (bool):
            If `True`, collect :pep:`526`-annotated attributes from the class
            body.

            In this case, you **must** annotate every field.  If *attrs*
            encounters a field that is set to an `attr.ib` but lacks a type
            annotation, an `attrs.exceptions.UnannotatedAttributeError` is
            raised.  Use ``field_name: typing.Any = attr.ib(...)`` if you don't
            want to set a type.

            If you assign a value to those attributes (for example, ``x: int =
            42``), that value becomes the default value like if it were passed
            using ``attr.ib(default=42)``.  Passing an instance of
            `attrs.Factory` also works as expected in most cases (see warning
            below).

            Attributes annotated as `typing.ClassVar`, and attributes that are
            neither annotated nor set to an `attr.ib` are **ignored**.

            .. warning::

                For features that use the attribute name to create decorators
                (for example, :ref:`validators <validators>`), you still *must*
                assign `attr.ib` to them. Otherwise Python will either not find
                the name or try to use the default value to call, for example,
                ``validator`` on it.

        kw_only (bool):
            Make all attributes keyword-only in the generated ``__init__`` (if
            *init* is `False`, this parameter is ignored).

        cache_hash (bool):
            Ensure that the object's hash code is computed only once and stored
            on the object.  If this is set to `True`, hashing must be either
            explicitly or implicitly enabled for this class.  If the hash code
            is cached, avoid any reassignments of fields involved in hash code
            computation or mutations of the objects those fields point to after
            object creation.  If such changes occur, the behavior of the
            object's hash code is undefined.

        auto_exc (bool):
            If the class subclasses `BaseException` (which implicitly includes
            any subclass of any exception), the following happens to behave
            like a well-behaved Python exceptions class:

            - the values for *eq*, *order*, and *hash* are ignored and the
              instances compare and hash by the instance's ids (N.B. *attrs*
              will *not* remove existing implementations of ``__hash__`` or the
              equality methods. It just won't add own ones.),
            - all attributes that are either passed into ``__init__`` or have a
              default value are additionally available as a tuple in the
              ``args`` attribute,
            - the value of *str* is ignored leaving ``__str__`` to base
              classes.

        collect_by_mro (bool):
            Setting this to `True` fixes the way *attrs* collects attributes
            from base classes.  The default behavior is incorrect in certain
            cases of multiple inheritance.  It should be on by default, but is
            kept off for backwards-compatibility.

            .. seealso::
                Issue `#428 <https://github.com/python-attrs/attrs/issues/428>`_

        getstate_setstate (bool | None):
            .. note::

                This is usually only interesting for slotted classes and you
                should probably just set *auto_detect* to `True`.

            If `True`, ``__getstate__`` and ``__setstate__`` are generated and
            attached to the class. This is necessary for slotted classes to be
            pickleable. If left `None`, it's `True` by default for slotted
            classes and `False` for dict classes.

            If *auto_detect* is `True`, and *getstate_setstate* is left `None`,
            and **either** ``__getstate__`` or ``__setstate__`` is detected
            directly on the class (meaning: not inherited), it is set to
            `False` (this is usually what you want).

        on_setattr (~typing.Callable | list[~typing.Callable] | None | typing.Literal[attrs.setters.NO_OP]):
            A callable that is run whenever the user attempts to set an
            attribute (either by assignment like ``i.x = 42`` or by using
            `setattr` like ``setattr(i, "x", 42)``). It receives the same
            arguments as validators: the instance, the attribute that is being
            modified, and the new value.

            If no exception is raised, the attribute is set to the return value
            of the callable.

            If a list of callables is passed, they're automatically wrapped in
            an `attrs.setters.pipe`.

        field_transformer (~typing.Callable | None):
            A function that is called with the original class object and all
            fields right before *attrs* finalizes the class.  You can use this,
            for example, to automatically add converters or validators to
            fields based on their types.

            .. seealso:: `transform-fields`

        match_args (bool):
            If `True` (default), set ``__match_args__`` on the class to support
            :pep:`634` (*Structural Pattern Matching*). It is a tuple of all
            non-keyword-only ``__init__`` parameter names on Python 3.10 and
            later. Ignored on older Python versions.

    :param bool only_non_default_attr_in_repr:
        If `False` (default), then the usual ``attrs`` repr is created. If `True`
        then only parameters set to their non-default values will be printed.
        This means when this is set to `True` the repr output is dynamic based
        on the state of the class.

    .. versionadded:: 16.0.0 *slots*
    .. versionadded:: 16.1.0 *frozen*
    .. versionadded:: 16.3.0 *str*
    .. versionadded:: 16.3.0 Support for ``__attrs_post_init__``.
    .. versionchanged:: 17.1.0
       *hash* supports `None` as value which is also the default now.
    .. versionadded:: 17.3.0 *auto_attribs*
    .. versionchanged:: 18.1.0
       If *these* is passed, no attributes are deleted from the class body.
    .. versionchanged:: 18.1.0 If *these* is ordered, the order is retained.
    .. versionadded:: 18.2.0 *weakref_slot*
    .. deprecated:: 18.2.0
       ``__lt__``, ``__le__``, ``__gt__``, and ``__ge__`` now raise a
       `DeprecationWarning` if the classes compared are subclasses of
       each other. ``__eq`` and ``__ne__`` never tried to compared subclasses
       to each other.
    .. versionchanged:: 19.2.0
       ``__lt__``, ``__le__``, ``__gt__``, and ``__ge__`` now do not consider
       subclasses comparable anymore.
    .. versionadded:: 18.2.0 *kw_only*
    .. versionadded:: 18.2.0 *cache_hash*
    .. versionadded:: 19.1.0 *auto_exc*
    .. deprecated:: 19.2.0 *cmp* Removal on or after 2021-06-01.
    .. versionadded:: 19.2.0 *eq* and *order*
    .. versionadded:: 20.1.0 *auto_detect*
    .. versionadded:: 20.1.0 *collect_by_mro*
    .. versionadded:: 20.1.0 *getstate_setstate*
    .. versionadded:: 20.1.0 *on_setattr*
    .. versionadded:: 20.3.0 *field_transformer*
    .. versionchanged:: 21.1.0
       ``init=False`` injects ``__attrs_init__``
    .. versionchanged:: 21.1.0 Support for ``__attrs_pre_init__``
    .. versionchanged:: 21.1.0 *cmp* undeprecated
    .. versionadded:: 21.3.0 *match_args*
    .. versionadded:: 22.2.0
       *unsafe_hash* as an alias for *hash* (for :pep:`681` compliance).
    .. deprecated:: 24.1.0 *repr_ns*
    .. versionadded:: 24.1
       *only_non_default_attr_in_repr* added to allow users to choose to have their
       classes dynamically include only those parameters whose values are set to
       non-default values in the repr.
    """
    if repr_ns is not None:
        import warnings

        warnings.warn(
            DeprecationWarning(
                "The `repr_ns` argument is deprecated and will be removed in or after April 2025."
            ),
            stacklevel=2,
        )

    eq_, order_ = _determine_attrs_eq_order(cmp, eq, order, None)

    # unsafe_hash takes precedence due to PEP 681.
    if unsafe_hash is not None:
        hash = unsafe_hash

    if isinstance(on_setattr, (list, tuple)):
        on_setattr = setters.pipe(*on_setattr)

    def wrap(cls):
        is_frozen = frozen or _has_frozen_base_class(cls)
        is_exc = auto_exc is True and issubclass(cls, BaseException)
        has_own_setattr = auto_detect and _has_own_attribute(
            cls, "__setattr__"
        )

        if has_own_setattr and is_frozen:
            msg = "Can't freeze a class with a custom __setattr__."
            raise ValueError(msg)

        builder = _ClassBuilder(
            cls,
            these,
            slots,
            is_frozen,
            weakref_slot,
            _determine_whether_to_implement(
                cls,
                getstate_setstate,
                auto_detect,
                ("__getstate__", "__setstate__"),
                default=slots,
            ),
            auto_attribs,
            kw_only,
            cache_hash,
            is_exc,
            collect_by_mro,
            on_setattr,
            has_own_setattr,
            field_transformer,
        )
        if _determine_whether_to_implement(
            cls, repr, auto_detect, ("__repr__",)
        ):
            builder.add_repr(
                repr_ns,
                only_non_default_attr_in_repr=only_non_default_attr_in_repr,
            )
        if str is True:
            builder.add_str()

        eq = _determine_whether_to_implement(
            cls, eq_, auto_detect, ("__eq__", "__ne__")
        )
        if not is_exc and eq is True:
            builder.add_eq()
        if not is_exc and _determine_whether_to_implement(
            cls, order_, auto_detect, ("__lt__", "__le__", "__gt__", "__ge__")
        ):
            builder.add_order()

        builder.add_setattr()

        nonlocal hash
        if (
            hash is None
            and auto_detect is True
            and _has_own_attribute(cls, "__hash__")
        ):
            hash = False

        if hash is not True and hash is not False and hash is not None:
            # Can't use `hash in` because 1 == True for example.
            msg = "Invalid value for hash.  Must be True, False, or None."
            raise TypeError(msg)

        if hash is False or (hash is None and eq is False) or is_exc:
            # Don't do anything. Should fall back to __object__'s __hash__
            # which is by id.
            if cache_hash:
                msg = "Invalid value for cache_hash.  To use hash caching, hashing must be either explicitly or implicitly enabled."
                raise TypeError(msg)
        elif hash is True or (
            hash is None and eq is True and is_frozen is True
        ):
            # Build a __hash__ if told so, or if it's safe.
            builder.add_hash()
        else:
            # Raise TypeError on attempts to hash.
            if cache_hash:
                msg = "Invalid value for cache_hash.  To use hash caching, hashing must be either explicitly or implicitly enabled."
                raise TypeError(msg)
            builder.make_unhashable()

        if _determine_whether_to_implement(
            cls, init, auto_detect, ("__init__",)
        ):
            builder.add_init()
        else:
            builder.add_attrs_init()
            if cache_hash:
                msg = "Invalid value for cache_hash.  To use hash caching, init must be True."
                raise TypeError(msg)

        if (
            PY_3_10_PLUS
            and match_args
            and not _has_own_attribute(cls, "__match_args__")
        ):
            builder.add_match_args()

        return builder.build_class()

    # 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

    return wrap(maybe_cls)


_attrs = attrs
"""
Internal alias so we can use it in functions that take an argument called
*attrs*.
"""


def _has_frozen_base_class(cls):
    """
    Check whether *cls* has a frozen ancestor by looking at its
    __setattr__.
    """
    return cls.__setattr__ is _frozen_setattrs


def _generate_unique_filename(cls, func_name):
    """
    Create a "filename" suitable for a function being generated.
    """
    return (
        f"<attrs generated {func_name} {cls.__module__}."
        f"{getattr(cls, '__qualname__', cls.__name__)}>"
    )


def _make_hash(cls, attrs, frozen, cache_hash):
    attrs = tuple(
        a for a in attrs if a.hash is True or (a.hash is None and a.eq is True)
    )

    tab = "        "

    unique_filename = _generate_unique_filename(cls, "hash")
    type_hash = hash(unique_filename)
    # If eq is custom generated, we need to include the functions in globs
    globs = {}

    hash_def = "def __hash__(self"
    hash_func = "hash(("
    closing_braces = "))"
    if not cache_hash:
        hash_def += "):"
    else:
        hash_def += ", *"

        hash_def += ", _cache_wrapper=__import__('attr._make')._make._CacheHashWrapper):"
        hash_func = "_cache_wrapper(" + hash_func
        closing_braces += ")"

    method_lines = [hash_def]

    def append_hash_computation_lines(prefix, indent):
        """
        Generate the code for actually computing the hash code.
        Below this will either be returned directly or used to compute
        a value which is then cached, depending on the value of cache_hash
        """

        method_lines.extend(
            [
                indent + prefix + hash_func,
                indent + f"        {type_hash},",
            ]
        )

        for a in attrs:
            if a.eq_key:
                cmp_name = f"_{a.name}_key"
                globs[cmp_name] = a.eq_key
                method_lines.append(
                    indent + f"        {cmp_name}(self.{a.name}),"
                )
            else:
                method_lines.append(indent + f"        self.{a.name},")

        method_lines.append(indent + "    " + closing_braces)

    if cache_hash:
        method_lines.append(tab + f"if self.{_HASH_CACHE_FIELD} is None:")
        if frozen:
            append_hash_computation_lines(
                f"object.__setattr__(self, '{_HASH_CACHE_FIELD}', ", tab * 2
            )
            method_lines.append(tab * 2 + ")")  # close __setattr__
        else:
            append_hash_computation_lines(
                f"self.{_HASH_CACHE_FIELD} = ", tab * 2
            )
        method_lines.append(tab + f"return self.{_HASH_CACHE_FIELD}")
    else:
        append_hash_computation_lines("return ", tab)

    script = "\n".join(method_lines)
    return _make_method("__hash__", script, unique_filename, globs)


def _add_hash(cls, attrs):
    """
    Add a hash method to *cls*.
    """
    cls.__hash__ = _make_hash(cls, attrs, frozen=False, cache_hash=False)
    return cls


def _make_ne():
    """
    Create __ne__ method.
    """

    def __ne__(self, other):
        """
        Check equality and either forward a NotImplemented or
        return the result negated.
        """
        result = self.__eq__(other)
        if result is NotImplemented:
            return NotImplemented

        return not result

    return __ne__


def _make_eq(cls, attrs):
    """
    Create __eq__ method for *cls* with *attrs*.
    """
    attrs = [a for a in attrs if a.eq]

    unique_filename = _generate_unique_filename(cls, "eq")
    lines = [
        "def __eq__(self, other):",
        "    if other.__class__ is not self.__class__:",
        "        return NotImplemented",
    ]

    # We can't just do a big self.x = other.x and... clause due to
    # irregularities like nan == nan is false but (nan,) == (nan,) is true.
    globs = {}
    if attrs:
        lines.append("    return  (")
        for a in attrs:
            if a.eq_key:
                cmp_name = f"_{a.name}_key"
                # Add the key function to the global namespace
                # of the evaluated function.
                globs[cmp_name] = a.eq_key
                lines.append(
                    f"        {cmp_name}(self.{a.name}) == {cmp_name}(other.{a.name})"
                )
            else:
                lines.append(f"        self.{a.name} == other.{a.name}")
            if a is not attrs[-1]:
                lines[-1] = f"{lines[-1]} and"
        lines.append("    )")
    else:
        lines.append("    return True")

    script = "\n".join(lines)

    return _make_method("__eq__", script, unique_filename, globs)


def _make_order(cls, attrs):
    """
    Create ordering methods for *cls* with *attrs*.
    """
    attrs = [a for a in attrs if a.order]

    def attrs_to_tuple(obj):
        """
        Save us some typing.
        """
        return tuple(
            key(value) if key else value
            for value, key in (
                (getattr(obj, a.name), a.order_key) for a in attrs
            )
        )

    def __lt__(self, other):
        """
        Automatically created by attrs.
        """
        if other.__class__ is self.__class__:
            return attrs_to_tuple(self) < attrs_to_tuple(other)

        return NotImplemented

    def __le__(self, other):
        """
        Automatically created by attrs.
        """
        if other.__class__ is self.__class__:
            return attrs_to_tuple(self) <= attrs_to_tuple(other)

        return NotImplemented

    def __gt__(self, other):
        """
        Automatically created by attrs.
        """
        if other.__class__ is self.__class__:
            return attrs_to_tuple(self) > attrs_to_tuple(other)

        return NotImplemented

    def __ge__(self, other):
        """
        Automatically created by attrs.
        """
        if other.__class__ is self.__class__:
            return attrs_to_tuple(self) >= attrs_to_tuple(other)

        return NotImplemented

    return __lt__, __le__, __gt__, __ge__


def _add_eq(cls, attrs=None):
    """
    Add equality methods to *cls* with *attrs*.
    """
    if attrs is None:
        attrs = cls.__attrs_attrs__

    cls.__eq__ = _make_eq(cls, attrs)
    cls.__ne__ = _make_ne()

    return cls


def _make_repr(attrs, ns, cls, only_non_default_attr_in_repr=False):
    unique_filename = _generate_unique_filename(cls, "repr")
    # Figure out which attributes to include, and which function to use to
    # format them. The a.repr value can be either bool or a custom
    # callable.
    attr_names_with_reprs = tuple(
        (a.name, (repr if a.repr is True else a.repr), a.init)
        for a in attrs
        if a.repr is not False
    )
    globs = {
        name + "_repr": r for name, r, _ in attr_names_with_reprs if r != repr
    }
    globs["_compat"] = _compat
    globs["AttributeError"] = AttributeError
    globs["NOTHING"] = NOTHING
    attribute_fragments = []
    for name, r, i in attr_names_with_reprs:
        accessor = (
            "self." + name if i else 'getattr(self, "' + name + '", NOTHING)'
        )
        fragment = (
            "%s={%s!r}" % (name, accessor)
            if r == repr
            else "%s={%s_repr(%s)}" % (name, name, accessor)
        )
        attribute_fragments.append(fragment)
    repr_fragment = ", ".join(attribute_fragments)

    if ns is None:
        cls_name_fragment = '{self.__class__.__qualname__.rsplit(">.", 1)[-1]}'
    else:
        cls_name_fragment = ns + ".{self.__class__.__name__}"

    lines = [
        "def __repr__(self):",
        "  try:",
        "    already_repring = _compat.repr_context.already_repring",
        "  except AttributeError:",
        "    already_repring = {id(self),}",
        "    _compat.repr_context.already_repring = already_repring",
        "  else:",
        "    if id(self) in already_repring:",
        "      return '...'",
        "    else:",
        "      already_repring.add(id(self))",
        "  try:",
        f"     if not {only_non_default_attr_in_repr}:",
        f"         return f'{cls_name_fragment}({repr_fragment})'",
        "     attr_frags = []",
        "     for a in getattr(self, '__attrs_attrs__', []):",
        "         value = getattr(self, a.name, NOTHING)",
        "         if hasattr(a.default, 'factory') and callable(a.default.factory):",
        "             if a.default.takes_self:",
        "                 default_ = a.default.factory(self)",
        "             else:",
        "                 default_ = a.default.factory()",
        "         else:",
        "             default_ = a.default",
        "         if (a.repr is False or value == default_):",
        "             frag = ''",
        "         else:",
        "             _repr = repr if a.repr is True else a.repr",
        "             frag = f'{a.name}={_repr(value)}'",
        "         attr_frags.append(frag)",
        "     repr_fragment = ', '.join(f for f in attr_frags if f != '')",
        f"     dynamic_repr = f'{cls_name_fragment}(' + repr_fragment + ')'",
        "     return dynamic_repr",
        "  finally:",
        "    already_repring.remove(id(self))",
    ]

    return _make_method(
        "__repr__", "\n".join(lines), unique_filename, globs=globs
    )


def _add_repr(cls, ns=None, attrs=None, only_non_default_attr_in_repr=False):
    """
    Add a repr method to *cls*.
    """
    if attrs is None:
        attrs = cls.__attrs_attrs__

    cls.__repr__ = _make_repr(
        attrs,
        ns,
        cls,
        only_non_default_attr_in_repr=only_non_default_attr_in_repr,
    )
    return cls


def fields(cls):
    """
    Return the tuple of *attrs* attributes for a class.

    The tuple also allows accessing the fields by their names (see below for
    examples).

    Args:
        cls (type): Class to introspect.

    Raises:
        TypeError: If *cls* is not a class.

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

    Returns:
        tuple (with name accessors) of `attrs.Attribute`

    .. versionchanged:: 16.2.0 Returned tuple allows accessing the fields
       by name.
    .. versionchanged:: 23.1.0 Add support for generic classes.
    """
    generic_base = get_generic_base(cls)

    if generic_base is None and not isinstance(cls, type):
        msg = "Passed object must be a class."
        raise TypeError(msg)

    attrs = getattr(cls, "__attrs_attrs__", None)

    if attrs is None:
        if generic_base is not None:
            attrs = getattr(generic_base, "__attrs_attrs__", None)
            if attrs is not None:
                # Even though this is global state, stick it on here to speed
                # it up. We rely on `cls` being cached for this to be
                # efficient.
                cls.__attrs_attrs__ = attrs
                return attrs
        msg = f"{cls!r} is not an attrs-decorated class."
        raise NotAnAttrsClassError(msg)

    return attrs


def fields_dict(cls):
    """
    Return an ordered dictionary of *attrs* attributes for a class, whose keys
    are the attribute names.

    Args:
        cls (type): Class to introspect.

    Raises:
        TypeError: If *cls* is not a class.

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

    Returns:
        dict[str, attrs.Attribute]: Dict of attribute name to definition

    .. versionadded:: 18.1.0
    """
    if not isinstance(cls, type):
        msg = "Passed object must be a class."
        raise TypeError(msg)
    attrs = getattr(cls, "__attrs_attrs__", None)
    if attrs is None:
        msg = f"{cls!r} is not an attrs-decorated class."
        raise NotAnAttrsClassError(msg)
    return {a.name: a for a in attrs}


def validate(inst):
    """
    Validate all attributes on *inst* that have a validator.

    Leaves all exceptions through.

    Args:
        inst: Instance of a class with *attrs* attributes.
    """
    if _config._run_validators is False:
        return

    for a in fields(inst.__class__):
        v = a.validator
        if v is not None:
            v(inst, a, getattr(inst, a.name))


def _is_slot_attr(a_name, base_attr_map):
    """
    Check if the attribute name comes from a slot class.
    """
    cls = base_attr_map.get(a_name)
    return cls and "__slots__" in cls.__dict__


def _make_init(
    cls,
    attrs,
    pre_init,
    pre_init_has_args,
    post_init,
    frozen,
    slots,
    cache_hash,
    base_attr_map,
    is_exc,
    cls_on_setattr,
    attrs_init,
):
    has_cls_on_setattr = (
        cls_on_setattr is not None and cls_on_setattr is not setters.NO_OP
    )

    if frozen and has_cls_on_setattr:
        msg = "Frozen classes can't use on_setattr."
        raise ValueError(msg)

    needs_cached_setattr = cache_hash or frozen
    filtered_attrs = []
    attr_dict = {}
    for a in attrs:
        if not a.init and a.default is NOTHING:
            continue

        filtered_attrs.append(a)
        attr_dict[a.name] = a

        if a.on_setattr is not None:
            if frozen is True:
                msg = "Frozen classes can't use on_setattr."
                raise ValueError(msg)

            needs_cached_setattr = True
        elif has_cls_on_setattr and a.on_setattr is not setters.NO_OP:
            needs_cached_setattr = True

    unique_filename = _generate_unique_filename(cls, "init")

    script, globs, annotations = _attrs_to_init_script(
        filtered_attrs,
        frozen,
        slots,
        pre_init,
        pre_init_has_args,
        post_init,
        cache_hash,
        base_attr_map,
        is_exc,
        needs_cached_setattr,
        has_cls_on_setattr,
        "__attrs_init__" if attrs_init else "__init__",
    )
    if cls.__module__ in sys.modules:
        # This makes typing.get_type_hints(CLS.__init__) resolve string types.
        globs.update(sys.modules[cls.__module__].__dict__)

    globs.update({"NOTHING": NOTHING, "attr_dict": attr_dict})

    if needs_cached_setattr:
        # Save the lookup overhead in __init__ if we need to circumvent
        # setattr hooks.
        globs["_cached_setattr_get"] = _OBJ_SETATTR.__get__

    init = _make_method(
        "__attrs_init__" if attrs_init else "__init__",
        script,
        unique_filename,
        globs,
    )
    init.__annotations__ = annotations

    return init


def _setattr(attr_name: str, value_var: str, has_on_setattr: bool) -> str:
    """
    Use the cached object.setattr to set *attr_name* to *value_var*.
    """
    return f"_setattr('{attr_name}', {value_var})"


def _setattr_with_converter(
    attr_name: str, value_var: str, has_on_setattr: bool, converter: Converter
) -> str:
    """
    Use the cached object.setattr to set *attr_name* to *value_var*, but run
    its converter first.
    """
    return f"_setattr('{attr_name}', {converter._fmt_converter_call(attr_name, value_var)})"


def _assign(attr_name: str, value: str, has_on_setattr: bool) -> str:
    """
    Unless *attr_name* has an on_setattr hook, use normal assignment. Otherwise
    relegate to _setattr.
    """
    if has_on_setattr:
        return _setattr(attr_name, value, True)

    return f"self.{attr_name} = {value}"


def _assign_with_converter(
    attr_name: str, value_var: str, has_on_setattr: bool, converter: Converter
) -> str:
    """
    Unless *attr_name* has an on_setattr hook, use normal assignment after
    conversion. Otherwise relegate to _setattr_with_converter.
    """
    if has_on_setattr:
        return _setattr_with_converter(attr_name, value_var, True, converter)

    return f"self.{attr_name} = {converter._fmt_converter_call(attr_name, value_var)}"


def _determine_setters(
    frozen: bool, slots: bool, base_attr_map: dict[str, type]
):
    """
    Determine the correct setter functions based on whether a class is frozen
    and/or slotted.
    """
    if frozen is True:
        if slots is True:
            return (), _setattr, _setattr_with_converter

        # Dict frozen classes assign directly to __dict__.
        # But only if the attribute doesn't come from an ancestor slot
        # class.
        # Note _inst_dict will be used again below if cache_hash is True

        def fmt_setter(
            attr_name: str, value_var: str, has_on_setattr: bool
        ) -> str:
            if _is_slot_attr(attr_name, base_attr_map):
                return _setattr(attr_name, value_var, has_on_setattr)

            return f"_inst_dict['{attr_name}'] = {value_var}"

        def fmt_setter_with_converter(
            attr_name: str,
            value_var: str,
            has_on_setattr: bool,
            converter: Converter,
        ) -> str:
            if has_on_setattr or _is_slot_attr(attr_name, base_attr_map):
                return _setattr_with_converter(
                    attr_name, value_var, has_on_setattr, converter
                )

            return f"_inst_dict['{attr_name}'] = {converter._fmt_converter_call(attr_name, value_var)}"

        return (
            ("_inst_dict = self.__dict__",),
            fmt_setter,
            fmt_setter_with_converter,
        )

    # Not frozen -- we can just assign directly.
    return (), _assign, _assign_with_converter


def _attrs_to_init_script(
    attrs: list[Attribute],
    is_frozen: bool,
    is_slotted: bool,
    call_pre_init: bool,
    pre_init_has_args: bool,
    call_post_init: bool,
    does_cache_hash: bool,
    base_attr_map: dict[str, type],
    is_exc: bool,
    needs_cached_setattr: bool,
    has_cls_on_setattr: bool,
    method_name: str,
) -> tuple[str, dict, dict]:
    """
    Return a script of an initializer for *attrs*, a dict of globals, and
    annotations for the initializer.

    The globals are required by the generated script.
    """
    lines = ["self.__attrs_pre_init__()"] if call_pre_init else []

    if needs_cached_setattr:
        lines.append(
            # Circumvent the __setattr__ descriptor to save one lookup per
            # assignment. Note _setattr will be used again below if
            # does_cache_hash is True.
            "_setattr = _cached_setattr_get(self)"
        )

    extra_lines, fmt_setter, fmt_setter_with_converter = _determine_setters(
        is_frozen, is_slotted, base_attr_map
    )
    lines.extend(extra_lines)

    args = []
    kw_only_args = []
    attrs_to_validate = []

    # This is a dictionary of names to validator and converter callables.
    # Injecting this into __init__ globals lets us avoid lookups.
    names_for_globals = {}
    annotations = {"return": None}

    for a in attrs:
        if a.validator:
            attrs_to_validate.append(a)

        attr_name = a.name
        has_on_setattr = a.on_setattr is not None or (
            a.on_setattr is not setters.NO_OP and has_cls_on_setattr
        )
        # a.alias is set to maybe-mangled attr_name in _ClassBuilder if not
        # explicitly provided
        arg_name = a.alias

        has_factory = isinstance(a.default, Factory)
        maybe_self = "self" if has_factory and a.default.takes_self else ""

        if a.converter and not isinstance(a.converter, Converter):
            converter = Converter(a.converter)
        else:
            converter = a.converter

        if a.init is False:
            if has_factory:
                init_factory_name = _INIT_FACTORY_PAT % (a.name,)
                if converter is not None:
                    lines.append(
                        fmt_setter_with_converter(
                            attr_name,
                            init_factory_name + f"({maybe_self})",
                            has_on_setattr,
                            converter,
                        )
                    )
                    names_for_globals[converter._get_global_name(a.name)] = (
                        converter.converter
                    )
                else:
                    lines.append(
                        fmt_setter(
                            attr_name,
                            init_factory_name + f"({maybe_self})",
                            has_on_setattr,
                        )
                    )
                names_for_globals[init_factory_name] = a.default.factory
            elif converter is not None:
                lines.append(
                    fmt_setter_with_converter(
                        attr_name,
                        f"attr_dict['{attr_name}'].default",
                        has_on_setattr,
                        converter,
                    )
                )
                names_for_globals[converter._get_global_name(a.name)] = (
                    converter.converter
                )
            else:
                lines.append(
                    fmt_setter(
                        attr_name,
                        f"attr_dict['{attr_name}'].default",
                        has_on_setattr,
                    )
                )
        elif a.default is not NOTHING and not has_factory:
            arg = f"{arg_name}=attr_dict['{attr_name}'].default"
            if a.kw_only:
                kw_only_args.append(arg)
            else:
                args.append(arg)

            if converter is not None:
                lines.append(
                    fmt_setter_with_converter(
                        attr_name, arg_name, has_on_setattr, converter
                    )
                )
                names_for_globals[converter._get_global_name(a.name)] = (
                    converter.converter
                )
            else:
                lines.append(fmt_setter(attr_name, arg_name, has_on_setattr))

        elif has_factory:
            arg = f"{arg_name}=NOTHING"
            if a.kw_only:
                kw_only_args.append(arg)
            else:
                args.append(arg)
            lines.append(f"if {arg_name} is not NOTHING:")

            init_factory_name = _INIT_FACTORY_PAT % (a.name,)
            if converter is not None:
                lines.append(
                    "    "
                    + fmt_setter_with_converter(
                        attr_name, arg_name, has_on_setattr, converter
                    )
                )
                lines.append("else:")
                lines.append(
                    "    "
                    + fmt_setter_with_converter(
                        attr_name,
                        init_factory_name + "(" + maybe_self + ")",
                        has_on_setattr,
                        converter,
                    )
                )
                names_for_globals[converter._get_global_name(a.name)] = (
                    converter.converter
                )
            else:
                lines.append(
                    "    " + fmt_setter(attr_name, arg_name, has_on_setattr)
                )
                lines.append("else:")
                lines.append(
                    "    "
                    + fmt_setter(
                        attr_name,
                        init_factory_name + "(" + maybe_self + ")",
                        has_on_setattr,
                    )
                )
            names_for_globals[init_factory_name] = a.default.factory
        else:
            if a.kw_only:
                kw_only_args.append(arg_name)
            else:
                args.append(arg_name)

            if converter is not None:
                lines.append(
                    fmt_setter_with_converter(
                        attr_name, arg_name, has_on_setattr, converter
                    )
                )
                names_for_globals[converter._get_global_name(a.name)] = (
                    converter.converter
                )
            else:
                lines.append(fmt_setter(attr_name, arg_name, has_on_setattr))

        if a.init is True:
            if a.type is not None and converter is None:
                annotations[arg_name] = a.type
            elif converter is not None and converter._first_param_type:
                # Use the type from the converter if present.
                annotations[arg_name] = converter._first_param_type

    if attrs_to_validate:  # we can skip this if there are no validators.
        names_for_globals["_config"] = _config
        lines.append("if _config._run_validators is True:")
        for a in attrs_to_validate:
            val_name = "__attr_validator_" + a.name
            attr_name = "__attr_" + a.name
            lines.append(f"    {val_name}(self, {attr_name}, self.{a.name})")
            names_for_globals[val_name] = a.validator
            names_for_globals[attr_name] = a

    if call_post_init:
        lines.append("self.__attrs_post_init__()")

    # Because this is set only after __attrs_post_init__ is called, a crash
    # will result if post-init tries to access the hash code.  This seemed
    # preferable to setting this beforehand, in which case alteration to field
    # values during post-init combined with post-init accessing the hash code
    # would result in silent bugs.
    if does_cache_hash:
        if is_frozen:
            if is_slotted:
                init_hash_cache = f"_setattr('{_HASH_CACHE_FIELD}', None)"
            else:
                init_hash_cache = f"_inst_dict['{_HASH_CACHE_FIELD}'] = None"
        else:
            init_hash_cache = f"self.{_HASH_CACHE_FIELD} = None"
        lines.append(init_hash_cache)

    # For exceptions we rely on BaseException.__init__ for proper
    # initialization.
    if is_exc:
        vals = ",".join(f"self.{a.name}" for a in attrs if a.init)

        lines.append(f"BaseException.__init__(self, {vals})")

    args = ", ".join(args)
    pre_init_args = args
    if kw_only_args:
        args += "%s*, %s" % (
            ", " if args else "",  # leading comma
            ", ".join(kw_only_args),  # kw_only args
        )
        pre_init_kw_only_args = ", ".join(
            ["%s=%s" % (kw_arg, kw_arg) for kw_arg in kw_only_args]
        )
        pre_init_args += (
            ", " if pre_init_args else ""
        )  # handle only kwargs and no regular args
        pre_init_args += pre_init_kw_only_args

    if call_pre_init and pre_init_has_args:
        # If pre init method has arguments, pass same arguments as `__init__`
        lines[0] = f"self.__attrs_pre_init__({pre_init_args})"

    return (
        f"def {method_name}(self, %s):\n    %s\n"
        % (
            args,
            "\n    ".join(lines) if lines else "pass",
        ),
        names_for_globals,
        annotations,
    )


def _default_init_alias_for(name: str) -> str:
    """
    The default __init__ parameter name for a field.

    This performs private-name adjustment via leading-unscore stripping,
    and is the default value of Attribute.alias if not provided.
    """

    return name.lstrip("_")


class Attribute:
    """
    *Read-only* representation of an attribute.

    .. warning::

       You should never instantiate this class yourself.

    The class has *all* arguments of `attr.ib` (except for ``factory`` which is
    only syntactic sugar for ``default=Factory(...)`` plus the following:

    - ``name`` (`str`): The name of the attribute.
    - ``alias`` (`str`): The __init__ parameter name of the attribute, after
      any explicit overrides and default private-attribute-name handling.
    - ``inherited`` (`bool`): Whether or not that attribute has been inherited
      from a base class.
    - ``eq_key`` and ``order_key`` (`typing.Callable` or `None`): The
      callables that are used for comparing and ordering objects by this
      attribute, respectively. These are set by passing a callable to
      `attr.ib`'s ``eq``, ``order``, or ``cmp`` arguments. See also
      :ref:`comparison customization <custom-comparison>`.

    Instances of this class are frequently used for introspection purposes
    like:

    - `fields` returns a tuple of them.
    - Validators get them passed as the first argument.
    - The :ref:`field transformer <transform-fields>` hook receives a list of
      them.
    - The ``alias`` property exposes the __init__ parameter name of the field,
      with any overrides and default private-attribute handling applied.


    .. versionadded:: 20.1.0 *inherited*
    .. versionadded:: 20.1.0 *on_setattr*
    .. versionchanged:: 20.2.0 *inherited* is not taken into account for
        equality checks and hashing anymore.
    .. versionadded:: 21.1.0 *eq_key* and *order_key*
    .. versionadded:: 22.2.0 *alias*

    For the full version history of the fields, see `attr.ib`.
    """

    __slots__ = (
        "name",
        "default",
        "validator",
        "repr",
        "eq",
        "eq_key",
        "order",
        "order_key",
        "hash",
        "init",
        "metadata",
        "type",
        "converter",
        "kw_only",
        "inherited",
        "on_setattr",
        "alias",
    )

    def __init__(
        self,
        name,
        default,
        validator,
        repr,
        cmp,  # XXX: unused, remove along with other cmp code.
        hash,
        init,
        inherited,
        metadata=None,
        type=None,
        converter=None,
        kw_only=False,
        eq=None,
        eq_key=None,
        order=None,
        order_key=None,
        on_setattr=None,
        alias=None,
    ):
        eq, eq_key, order, order_key = _determine_attrib_eq_order(
            cmp, eq_key or eq, order_key or order, True
        )

        # Cache this descriptor here to speed things up later.
        bound_setattr = _OBJ_SETATTR.__get__(self)

        # Despite the big red warning, people *do* instantiate `Attribute`
        # themselves.
        bound_setattr("name", name)
        bound_setattr("default", default)
        bound_setattr("validator", validator)
        bound_setattr("repr", repr)
        bound_setattr("eq", eq)
        bound_setattr("eq_key", eq_key)
        bound_setattr("order", order)
        bound_setattr("order_key", order_key)
        bound_setattr("hash", hash)
        bound_setattr("init", init)
        bound_setattr("converter", converter)
        bound_setattr(
            "metadata",
            (
                types.MappingProxyType(dict(metadata))  # Shallow copy
                if metadata
                else _EMPTY_METADATA_SINGLETON
            ),
        )
        bound_setattr("type", type)
        bound_setattr("kw_only", kw_only)
        bound_setattr("inherited", inherited)
        bound_setattr("on_setattr", on_setattr)
        bound_setattr("alias", alias)

    def __setattr__(self, name, value):
        raise FrozenInstanceError()

    @classmethod
    def from_counting_attr(cls, name, ca, type=None):
        # type holds the annotated value. deal with conflicts:
        if type is None:
            type = ca.type
        elif ca.type is not None:
            msg = "Type annotation and type argument cannot both be present"
            raise ValueError(msg)
        inst_dict = {
            k: getattr(ca, k)
            for k in Attribute.__slots__
            if k
            not in (
                "name",
                "validator",
                "default",
                "type",
                "inherited",
            )  # exclude methods and deprecated alias
        }
        return cls(
            name=name,
            validator=ca._validator,
            default=ca._default,
            type=type,
            cmp=None,
            inherited=False,
            **inst_dict,
        )

    # Don't use attrs.evolve since fields(Attribute) doesn't work
    def evolve(self, **changes):
        """
        Copy *self* and apply *changes*.

        This works similarly to `attrs.evolve` but that function does not work
        with `Attribute`.

        It is mainly meant to be used for `transform-fields`.

        .. versionadded:: 20.3.0
        """
        new = copy.copy(self)

        new._setattrs(changes.items())

        return new

    # Don't use _add_pickle since fields(Attribute) doesn't work
    def __getstate__(self):
        """
        Play nice with pickle.
        """
        return tuple(
            getattr(self, name) if name != "metadata" else dict(self.metadata)
            for name in self.__slots__
        )

    def __setstate__(self, state):
        """
        Play nice with pickle.
        """
        self._setattrs(zip(self.__slots__, state))

    def _setattrs(self, name_values_pairs):
        bound_setattr = _OBJ_SETATTR.__get__(self)
        for name, value in name_values_pairs:
            if name != "metadata":
                bound_setattr(name, value)
            else:
                bound_setattr(
                    name,
                    (
                        types.MappingProxyType(dict(value))
                        if value
                        else _EMPTY_METADATA_SINGLETON
                    ),
                )


_a = [
    Attribute(
        name=name,
        default=NOTHING,
        validator=None,
        repr=True,
        cmp=None,
        eq=True,
        order=False,
        hash=(name != "metadata"),
        init=True,
        inherited=False,
        alias=_default_init_alias_for(name),
    )
    for name in Attribute.__slots__
]

Attribute = _add_hash(
    _add_eq(
        _add_repr(Attribute, attrs=_a),
        attrs=[a for a in _a if a.name != "inherited"],
    ),
    attrs=[a for a in _a if a.hash and a.name != "inherited"],
)


class _CountingAttr:
    """
    Intermediate representation of attributes that uses a counter to preserve
    the order in which the attributes have been defined.

    *Internal* data structure of the attrs library.  Running into is most
    likely the result of a bug like a forgotten `@attr.s` decorator.
    """

    __slots__ = (
        "counter",
        "_default",
        "repr",
        "eq",
        "eq_key",
        "order",
        "order_key",
        "hash",
        "init",
        "metadata",
        "_validator",
        "converter",
        "type",
        "kw_only",
        "on_setattr",
        "alias",
    )
    __attrs_attrs__ = (
        *tuple(
            Attribute(
                name=name,
                alias=_default_init_alias_for(name),
                default=NOTHING,
                validator=None,
                repr=True,
                cmp=None,
                hash=True,
                init=True,
                kw_only=False,
                eq=True,
                eq_key=None,
                order=False,
                order_key=None,
                inherited=False,
                on_setattr=None,
            )
            for name in (
                "counter",
                "_default",
                "repr",
                "eq",
                "order",
                "hash",
                "init",
                "on_setattr",
                "alias",
            )
        ),
        Attribute(
            name="metadata",
            alias="metadata",
            default=None,
            validator=None,
            repr=True,
            cmp=None,
            hash=False,
            init=True,
            kw_only=False,
            eq=True,
            eq_key=None,
            order=False,
            order_key=None,
            inherited=False,
            on_setattr=None,
        ),
    )
    cls_counter = 0

    def __init__(
        self,
        default,
        validator,
        repr,
        cmp,
        hash,
        init,
        converter,
        metadata,
        type,
        kw_only,
        eq,
        eq_key,
        order,
        order_key,
        on_setattr,
        alias,
    ):
        _CountingAttr.cls_counter += 1
        self.counter = _CountingAttr.cls_counter
        self._default = default
        self._validator = validator
        self.converter = converter
        self.repr = repr
        self.eq = eq
        self.eq_key = eq_key
        self.order = order
        self.order_key = order_key
        self.hash = hash
        self.init = init
        self.metadata = metadata
        self.type = type
        self.kw_only = kw_only
        self.on_setattr = on_setattr
        self.alias = alias

    def validator(self, meth):
        """
        Decorator that adds *meth* to the list of validators.

        Returns *meth* unchanged.

        .. versionadded:: 17.1.0
        """
        if self._validator is None:
            self._validator = meth
        else:
            self._validator = and_(self._validator, meth)
        return meth

    def default(self, meth):
        """
        Decorator that allows to set the default for an attribute.

        Returns *meth* unchanged.

        Raises:
            DefaultAlreadySetError: If default has been set before.

        .. versionadded:: 17.1.0
        """
        if self._default is not NOTHING:
            raise DefaultAlreadySetError()

        self._default = Factory(meth, takes_self=True)

        return meth


_CountingAttr = _add_eq(_add_repr(_CountingAttr))


class Factory:
    """
    Stores a factory callable.

    If passed as the default value to `attrs.field`, the factory is used to
    generate a new value.

    Args:
        factory (typing.Callable):
            A callable that takes either none or exactly one mandatory
            positional argument depending on *takes_self*.

        takes_self (bool):
            Pass the partially initialized instance that is being initialized
            as a positional argument.

    .. versionadded:: 17.1.0  *takes_self*
    """

    __slots__ = ("factory", "takes_self")

    def __init__(self, factory, takes_self=False):
        self.factory = factory
        self.takes_self = takes_self

    def __getstate__(self):
        """
        Play nice with pickle.
        """
        return tuple(getattr(self, name) for name in self.__slots__)

    def __setstate__(self, state):
        """
        Play nice with pickle.
        """
        for name, value in zip(self.__slots__, state):
            setattr(self, name, value)


_f = [
    Attribute(
        name=name,
        default=NOTHING,
        validator=None,
        repr=True,
        cmp=None,
        eq=True,
        order=False,
        hash=True,
        init=True,
        inherited=False,
    )
    for name in Factory.__slots__
]

Factory = _add_hash(_add_eq(_add_repr(Factory, attrs=_f), attrs=_f), attrs=_f)


class Converter:
    """
    Stores a converter callable.

    Allows for the wrapped converter to take additional arguments. The
    arguments are passed in the order they are documented.

    Args:
        converter (Callable): A callable that converts the passed value.

        takes_self (bool):
            Pass the partially initialized instance that is being initialized
            as a positional argument. (default: `False`)

        takes_field (bool):
            Pass the field definition (an `Attribute`) into the converter as a
            positional argument. (default: `False`)

    .. versionadded:: 24.1.0
    """

    __slots__ = (
        "converter",
        "takes_self",
        "takes_field",
        "_first_param_type",
        "_global_name",
        "__call__",
    )

    def __init__(self, converter, *, takes_self=False, takes_field=False):
        self.converter = converter
        self.takes_self = takes_self
        self.takes_field = takes_field

        self._first_param_type = _AnnotationExtractor(
            converter
        ).get_first_param_type()

    @staticmethod
    def _get_global_name(attr_name: str) -> str:
        """
        Return the name that a converter for an attribute name *attr_name*
        would have.
        """
        return f"__attr_converter_{attr_name}"

    def _fmt_converter_call(self, attr_name: str, value_var: str) -> str:
        """
        Return a string that calls the converter for an attribute name
        *attr_name* and the value in variable named *value_var* according to
        `self.takes_self` and `self.takes_field`.
        """
        if not (self.takes_self or self.takes_field):
            return f"{self._get_global_name(attr_name)}({value_var})"

        if self.takes_self and self.takes_field:
            return f"{self._get_global_name(attr_name)}({value_var}, self, attr_dict['{attr_name}'])"

        if self.takes_self:
            return f"{self._get_global_name(attr_name)}({value_var}, self)"

        return f"{self._get_global_name(attr_name)}({value_var}, attr_dict['{attr_name}'])"

    def __getstate__(self):
        """
        Return a dict containing only converter and takes_self -- the rest gets
        computed when loading.
        """
        return {
            "converter": self.converter,
            "takes_self": self.takes_self,
            "takes_field": self.takes_field,
        }

    def __setstate__(self, state):
        """
        Load instance from state.
        """
        self.__init__(**state)


_f = [
    Attribute(
        name=name,
        default=NOTHING,
        validator=None,
        repr=True,
        cmp=None,
        eq=True,
        order=False,
        hash=True,
        init=True,
        inherited=False,
    )
    for name in ("converter", "takes_self", "takes_field")
]

Converter = _add_hash(
    _add_eq(_add_repr(Converter, attrs=_f), attrs=_f), attrs=_f
)


def make_class(
    name, attrs, bases=(object,), class_body=None, **attributes_arguments
):
    r"""
    A quick way to create a new class called *name* with *attrs*.

    Args:
        name (str): The name for the new class.

        attrs( list | dict):
            A list of names or a dictionary of mappings of names to `attr.ib`\
            s / `attrs.field`\ s.

            The order is deduced from the order of the names or attributes
            inside *attrs*.  Otherwise the order of the definition of the
            attributes is used.

        bases (tuple[type, ...]): Classes that the new class will subclass.

        class_body (dict):
            An optional dictionary of class attributes for the new class.

        attributes_arguments: Passed unmodified to `attr.s`.

    Returns:
        type: A new class with *attrs*.

    .. versionadded:: 17.1.0 *bases*
    .. versionchanged:: 18.1.0 If *attrs* is ordered, the order is retained.
    .. versionchanged:: 23.2.0 *class_body*
    """
    if isinstance(attrs, dict):
        cls_dict = attrs
    elif isinstance(attrs, (list, tuple)):
        cls_dict = {a: attrib() for a in attrs}
    else:
        msg = "attrs argument must be a dict or a list."
        raise TypeError(msg)

    pre_init = cls_dict.pop("__attrs_pre_init__", None)
    post_init = cls_dict.pop("__attrs_post_init__", None)
    user_init = cls_dict.pop("__init__", None)

    body = {}
    if class_body is not None:
        body.update(class_body)
    if pre_init is not None:
        body["__attrs_pre_init__"] = pre_init
    if post_init is not None:
        body["__attrs_post_init__"] = post_init
    if user_init is not None:
        body["__init__"] = user_init

    type_ = types.new_class(name, bases, {}, lambda ns: ns.update(body))

    # For pickling to work, the __module__ variable needs to be set to the
    # frame where the class is created.  Bypass this step in environments where
    # sys._getframe is not defined (Jython for example) or sys._getframe is not
    # defined for arguments greater than 0 (IronPython).
    with contextlib.suppress(AttributeError, ValueError):
        type_.__module__ = sys._getframe(1).f_globals.get(
            "__name__", "__main__"
        )

    # We do it here for proper warnings with meaningful stacklevel.
    cmp = attributes_arguments.pop("cmp", None)
    (
        attributes_arguments["eq"],
        attributes_arguments["order"],
    ) = _determine_attrs_eq_order(
        cmp,
        attributes_arguments.get("eq"),
        attributes_arguments.get("order"),
        True,
    )

    cls = _attrs(these=cls_dict, **attributes_arguments)(type_)
    # Only add type annotations now or "_attrs()" will complain:
    cls.__annotations__ = {
        k: v.type for k, v in cls_dict.items() if v.type is not None
    }
    return cls


# These are required by within this module so we define them here and merely
# import into .validators / .converters.


@attrs(slots=True, hash=True)
class _AndValidator:
    """
    Compose many validators to a single one.
    """

    _validators = attrib()

    def __call__(self, inst, attr, value):
        for v in self._validators:
            v(inst, attr, value)


def and_(*validators):
    """
    A validator that composes multiple validators into one.

    When called on a value, it runs all wrapped validators.

    Args:
        validators (~collections.abc.Iterable[typing.Callable]):
            Arbitrary number of validators.

    .. versionadded:: 17.1.0
    """
    vals = []
    for validator in validators:
        vals.extend(
            validator._validators
            if isinstance(validator, _AndValidator)
            else [validator]
        )

    return _AndValidator(tuple(vals))


def pipe(*converters):
    """
    A converter that composes multiple converters into one.

    When called on a value, it runs all wrapped converters, returning the
    *last* value.

    Type annotations will be inferred from the wrapped converters', if they
    have any.

        converters (~collections.abc.Iterable[typing.Callable]):
            Arbitrary number of converters.

    .. versionadded:: 20.1.0
    """

    def pipe_converter(val, inst, field):
        for c in converters:
            if isinstance(c, Converter):
                val = c.converter(
                    val,
                    *{
                        (False, False): (),
                        (True, False): (c.takes_self,),
                        (False, True): (c.takes_field,),
                        (True, True): (c.takes_self, c.takes_field),
                    }[c.takes_self, c.takes_field],
                )
            else:
                val = c(val)

        return val

    if not converters:
        # If the converter list is empty, pipe_converter is the identity.
        A = typing.TypeVar("A")
        pipe_converter.__annotations__.update({"val": A, "return": A})
    else:
        # Get parameter type from first converter.
        t = _AnnotationExtractor(converters[0]).get_first_param_type()
        if t:
            pipe_converter.__annotations__["val"] = t

        # Get return type from last converter.
        rt = _AnnotationExtractor(converters[-1]).get_return_type()
        if rt:
            pipe_converter.__annotations__["return"] = rt

    return Converter(pipe_converter, takes_self=True, takes_field=True)