_model_construction.py

"""Private logic for creating models."""
from __future__ import annotations as _annotations

import builtins
import operator
import typing
import warnings
import weakref
from abc import ABCMeta
from functools import partial
from types import FunctionType
from typing import Any, Callable, Generic, NoReturn

import typing_extensions
from pydantic_core import PydanticUndefined, SchemaSerializer
from typing_extensions import dataclass_transform, deprecated

from ..errors import PydanticUndefinedAnnotation, PydanticUserError
from ..plugin._schema_validator import create_schema_validator
from ..warnings import GenericBeforeBaseModelWarning, PydanticDeprecatedSince20
from ._config import ConfigWrapper
from ._decorators import DecoratorInfos, PydanticDescriptorProxy, get_attribute_from_bases, unwrap_wrapped_function
from ._fields import collect_model_fields, is_valid_field_name, is_valid_privateattr_name
from ._generate_schema import GenerateSchema
from ._generics import PydanticGenericMetadata, get_model_typevars_map
from ._mock_val_ser import set_model_mocks
from ._schema_generation_shared import CallbackGetCoreSchemaHandler
from ._signature import generate_pydantic_signature
from ._typing_extra import get_cls_types_namespace, is_annotated, is_classvar, parent_frame_namespace
from ._utils import ClassAttribute, SafeGetItemProxy
from ._validate_call import ValidateCallWrapper

if typing.TYPE_CHECKING:
    from ..fields import Field as PydanticModelField
    from ..fields import FieldInfo, ModelPrivateAttr
    from ..main import BaseModel
else:
    # See PyCharm issues https://youtrack.jetbrains.com/issue/PY-21915
    # and https://youtrack.jetbrains.com/issue/PY-51428
    DeprecationWarning = PydanticDeprecatedSince20
    PydanticModelField = object()

object_setattr = object.__setattr__


class _ModelNamespaceDict(dict):
    """A dictionary subclass that intercepts attribute setting on model classes and
    warns about overriding of decorators.
    """

    def __setitem__(self, k: str, v: object) -> None:
        existing: Any = self.get(k, None)
        if existing and v is not existing and isinstance(existing, PydanticDescriptorProxy):
            warnings.warn(f'`{k}` overrides an existing Pydantic `{existing.decorator_info.decorator_repr}` decorator')

        return super().__setitem__(k, v)


@dataclass_transform(kw_only_default=True, field_specifiers=(PydanticModelField,))
class ModelMetaclass(ABCMeta):
    def __new__(
        mcs,
        cls_name: str,
        bases: tuple[type[Any], ...],
        namespace: dict[str, Any],
        __pydantic_generic_metadata__: PydanticGenericMetadata | None = None,
        __pydantic_reset_parent_namespace__: bool = True,
        _create_model_module: str | None = None,
        **kwargs: Any,
    ) -> type:
        """Metaclass for creating Pydantic models.

        Args:
            cls_name: The name of the class to be created.
            bases: The base classes of the class to be created.
            namespace: The attribute dictionary of the class to be created.
            __pydantic_generic_metadata__: Metadata for generic models.
            __pydantic_reset_parent_namespace__: Reset parent namespace.
            _create_model_module: The module of the class to be created, if created by `create_model`.
            **kwargs: Catch-all for any other keyword arguments.

        Returns:
            The new class created by the metaclass.
        """
        # Note `ModelMetaclass` refers to `BaseModel`, but is also used to *create* `BaseModel`, so we rely on the fact
        # that `BaseModel` itself won't have any bases, but any subclass of it will, to determine whether the `__new__`
        # call we're in the middle of is for the `BaseModel` class.
        if bases:
            base_field_names, class_vars, base_private_attributes = mcs._collect_bases_data(bases)

            config_wrapper = ConfigWrapper.for_model(bases, namespace, kwargs)
            namespace['model_config'] = config_wrapper.config_dict
            private_attributes = inspect_namespace(
                namespace, config_wrapper.ignored_types, class_vars, base_field_names
            )
            if private_attributes:
                original_model_post_init = get_model_post_init(namespace, bases)
                if original_model_post_init is not None:
                    # if there are private_attributes and a model_post_init function, we handle both

                    def wrapped_model_post_init(self: BaseModel, __context: Any) -> None:
                        """We need to both initialize private attributes and call the user-defined model_post_init
                        method.
                        """
                        init_private_attributes(self, __context)
                        original_model_post_init(self, __context)

                    namespace['model_post_init'] = wrapped_model_post_init
                else:
                    namespace['model_post_init'] = init_private_attributes

            namespace['__class_vars__'] = class_vars
            namespace['__private_attributes__'] = {**base_private_attributes, **private_attributes}

            cls: type[BaseModel] = super().__new__(mcs, cls_name, bases, namespace, **kwargs)  # type: ignore

            from ..main import BaseModel

            mro = cls.__mro__
            if Generic in mro and mro.index(Generic) < mro.index(BaseModel):
                warnings.warn(
                    GenericBeforeBaseModelWarning(
                        'Classes should inherit from `BaseModel` before generic classes (e.g. `typing.Generic[T]`) '
                        'for pydantic generics to work properly.'
                    ),
                    stacklevel=2,
                )

            cls.__pydantic_custom_init__ = not getattr(cls.__init__, '__pydantic_base_init__', False)
            cls.__pydantic_post_init__ = None if cls.model_post_init is BaseModel.model_post_init else 'model_post_init'

            cls.__pydantic_decorators__ = DecoratorInfos.build(cls)

            # Use the getattr below to grab the __parameters__ from the `typing.Generic` parent class
            if __pydantic_generic_metadata__:
                cls.__pydantic_generic_metadata__ = __pydantic_generic_metadata__
            else:
                parent_parameters = getattr(cls, '__pydantic_generic_metadata__', {}).get('parameters', ())
                parameters = getattr(cls, '__parameters__', None) or parent_parameters
                if parameters and parent_parameters and not all(x in parameters for x in parent_parameters):
                    from ..root_model import RootModelRootType

                    missing_parameters = tuple(x for x in parameters if x not in parent_parameters)
                    if RootModelRootType in parent_parameters and RootModelRootType not in parameters:
                        # This is a special case where the user has subclassed `RootModel`, but has not parametrized
                        # RootModel with the generic type identifiers being used. Ex:
                        # class MyModel(RootModel, Generic[T]):
                        #    root: T
                        # Should instead just be:
                        # class MyModel(RootModel[T]):
                        #   root: T
                        parameters_str = ', '.join([x.__name__ for x in missing_parameters])
                        error_message = (
                            f'{cls.__name__} is a subclass of `RootModel`, but does not include the generic type identifier(s) '
                            f'{parameters_str} in its parameters. '
                            f'You should parametrize RootModel directly, e.g., `class {cls.__name__}(RootModel[{parameters_str}]): ...`.'
                        )
                    else:
                        combined_parameters = parent_parameters + missing_parameters
                        parameters_str = ', '.join([str(x) for x in combined_parameters])
                        generic_type_label = f'typing.Generic[{parameters_str}]'
                        error_message = (
                            f'All parameters must be present on typing.Generic;'
                            f' you should inherit from {generic_type_label}.'
                        )
                        if Generic not in bases:  # pragma: no cover
                            # We raise an error here not because it is desirable, but because some cases are mishandled.
                            # It would be nice to remove this error and still have things behave as expected, it's just
                            # challenging because we are using a custom `__class_getitem__` to parametrize generic models,
                            # and not returning a typing._GenericAlias from it.
                            bases_str = ', '.join([x.__name__ for x in bases] + [generic_type_label])
                            error_message += (
                                f' Note: `typing.Generic` must go last: `class {cls.__name__}({bases_str}): ...`)'
                            )
                    raise TypeError(error_message)

                cls.__pydantic_generic_metadata__ = {
                    'origin': None,
                    'args': (),
                    'parameters': parameters,
                }

            cls.__pydantic_complete__ = False  # Ensure this specific class gets completed

            # preserve `__set_name__` protocol defined in https://peps.python.org/pep-0487
            # for attributes not in `new_namespace` (e.g. private attributes)
            for name, obj in private_attributes.items():
                obj.__set_name__(cls, name)

            if __pydantic_reset_parent_namespace__:
                cls.__pydantic_parent_namespace__ = build_lenient_weakvaluedict(parent_frame_namespace())
            parent_namespace = getattr(cls, '__pydantic_parent_namespace__', None)
            if isinstance(parent_namespace, dict):
                parent_namespace = unpack_lenient_weakvaluedict(parent_namespace)

            types_namespace = get_cls_types_namespace(cls, parent_namespace)
            set_model_fields(cls, bases, config_wrapper, types_namespace)

            if config_wrapper.frozen and '__hash__' not in namespace:
                set_default_hash_func(cls, bases)

            complete_model_class(
                cls,
                cls_name,
                config_wrapper,
                raise_errors=False,
                types_namespace=types_namespace,
                create_model_module=_create_model_module,
            )

            # If this is placed before the complete_model_class call above,
            # the generic computed fields return type is set to PydanticUndefined
            cls.model_computed_fields = {k: v.info for k, v in cls.__pydantic_decorators__.computed_fields.items()}

            set_deprecated_descriptors(cls)

            # using super(cls, cls) on the next line ensures we only call the parent class's __pydantic_init_subclass__
            # I believe the `type: ignore` is only necessary because mypy doesn't realize that this code branch is
            # only hit for _proper_ subclasses of BaseModel
            super(cls, cls).__pydantic_init_subclass__(**kwargs)  # type: ignore[misc]
            return cls
        else:
            # this is the BaseModel class itself being created, no logic required
            return super().__new__(mcs, cls_name, bases, namespace, **kwargs)

    if not typing.TYPE_CHECKING:  # pragma: no branch
        # We put `__getattr__` in a non-TYPE_CHECKING block because otherwise, mypy allows arbitrary attribute access

        def __getattr__(self, item: str) -> Any:
            """This is necessary to keep attribute access working for class attribute access."""
            private_attributes = self.__dict__.get('__private_attributes__')
            if private_attributes and item in private_attributes:
                return private_attributes[item]
            raise AttributeError(item)

    @classmethod
    def __prepare__(cls, *args: Any, **kwargs: Any) -> dict[str, object]:
        return _ModelNamespaceDict()

    def __instancecheck__(self, instance: Any) -> bool:
        """Avoid calling ABC _abc_subclasscheck unless we're pretty sure.

        See #3829 and python/cpython#92810
        """
        return hasattr(instance, '__pydantic_validator__') and super().__instancecheck__(instance)

    @staticmethod
    def _collect_bases_data(bases: tuple[type[Any], ...]) -> tuple[set[str], set[str], dict[str, ModelPrivateAttr]]:
        from ..main import BaseModel

        field_names: set[str] = set()
        class_vars: set[str] = set()
        private_attributes: dict[str, ModelPrivateAttr] = {}
        for base in bases:
            if issubclass(base, BaseModel) and base is not BaseModel:
                # model_fields might not be defined yet in the case of generics, so we use getattr here:
                field_names.update(getattr(base, 'model_fields', {}).keys())
                class_vars.update(base.__class_vars__)
                private_attributes.update(base.__private_attributes__)
        return field_names, class_vars, private_attributes

    @property
    @deprecated('The `__fields__` attribute is deprecated, use `model_fields` instead.', category=None)
    def __fields__(self) -> dict[str, FieldInfo]:
        warnings.warn(
            'The `__fields__` attribute is deprecated, use `model_fields` instead.', PydanticDeprecatedSince20
        )
        return self.model_fields  # type: ignore

    def __dir__(self) -> list[str]:
        attributes = list(super().__dir__())
        if '__fields__' in attributes:
            attributes.remove('__fields__')
        return attributes


def init_private_attributes(self: BaseModel, __context: Any) -> None:
    """This function is meant to behave like a BaseModel method to initialise private attributes.

    It takes context as an argument since that's what pydantic-core passes when calling it.

    Args:
        self: The BaseModel instance.
        __context: The context.
    """
    if getattr(self, '__pydantic_private__', None) is None:
        pydantic_private = {}
        for name, private_attr in self.__private_attributes__.items():
            default = private_attr.get_default()
            if default is not PydanticUndefined:
                pydantic_private[name] = default
        object_setattr(self, '__pydantic_private__', pydantic_private)


def get_model_post_init(namespace: dict[str, Any], bases: tuple[type[Any], ...]) -> Callable[..., Any] | None:
    """Get the `model_post_init` method from the namespace or the class bases, or `None` if not defined."""
    if 'model_post_init' in namespace:
        return namespace['model_post_init']

    from ..main import BaseModel

    model_post_init = get_attribute_from_bases(bases, 'model_post_init')
    if model_post_init is not BaseModel.model_post_init:
        return model_post_init


def inspect_namespace(  # noqa C901
    namespace: dict[str, Any],
    ignored_types: tuple[type[Any], ...],
    base_class_vars: set[str],
    base_class_fields: set[str],
) -> dict[str, ModelPrivateAttr]:
    """Iterate over the namespace and:
    * gather private attributes
    * check for items which look like fields but are not (e.g. have no annotation) and warn.

    Args:
        namespace: The attribute dictionary of the class to be created.
        ignored_types: A tuple of ignore types.
        base_class_vars: A set of base class class variables.
        base_class_fields: A set of base class fields.

    Returns:
        A dict contains private attributes info.

    Raises:
        TypeError: If there is a `__root__` field in model.
        NameError: If private attribute name is invalid.
        PydanticUserError:
            - If a field does not have a type annotation.
            - If a field on base class was overridden by a non-annotated attribute.
    """
    from ..fields import FieldInfo, ModelPrivateAttr, PrivateAttr

    all_ignored_types = ignored_types + default_ignored_types()

    private_attributes: dict[str, ModelPrivateAttr] = {}
    raw_annotations = namespace.get('__annotations__', {})

    if '__root__' in raw_annotations or '__root__' in namespace:
        raise TypeError("To define root models, use `pydantic.RootModel` rather than a field called '__root__'")

    ignored_names: set[str] = set()
    for var_name, value in list(namespace.items()):
        if var_name == 'model_config':
            continue
        elif (
            isinstance(value, type)
            and value.__module__ == namespace['__module__']
            and '__qualname__' in namespace
            and value.__qualname__.startswith(namespace['__qualname__'])
        ):
            # `value` is a nested type defined in this namespace; don't error
            continue
        elif isinstance(value, all_ignored_types) or value.__class__.__module__ == 'functools':
            ignored_names.add(var_name)
            continue
        elif isinstance(value, ModelPrivateAttr):
            if var_name.startswith('__'):
                raise NameError(
                    'Private attributes must not use dunder names;'
                    f' use a single underscore prefix instead of {var_name!r}.'
                )
            elif is_valid_field_name(var_name):
                raise NameError(
                    'Private attributes must not use valid field names;'
                    f' use sunder names, e.g. {"_" + var_name!r} instead of {var_name!r}.'
                )
            private_attributes[var_name] = value
            del namespace[var_name]
        elif isinstance(value, FieldInfo) and not is_valid_field_name(var_name):
            suggested_name = var_name.lstrip('_') or 'my_field'  # don't suggest '' for all-underscore name
            raise NameError(
                f'Fields must not use names with leading underscores;'
                f' e.g., use {suggested_name!r} instead of {var_name!r}.'
            )

        elif var_name.startswith('__'):
            continue
        elif is_valid_privateattr_name(var_name):
            if var_name not in raw_annotations or not is_classvar(raw_annotations[var_name]):
                private_attributes[var_name] = PrivateAttr(default=value)
                del namespace[var_name]
        elif var_name in base_class_vars:
            continue
        elif var_name not in raw_annotations:
            if var_name in base_class_fields:
                raise PydanticUserError(
                    f'Field {var_name!r} defined on a base class was overridden by a non-annotated attribute. '
                    f'All field definitions, including overrides, require a type annotation.',
                    code='model-field-overridden',
                )
            elif isinstance(value, FieldInfo):
                raise PydanticUserError(
                    f'Field {var_name!r} requires a type annotation', code='model-field-missing-annotation'
                )
            else:
                raise PydanticUserError(
                    f'A non-annotated attribute was detected: `{var_name} = {value!r}`. All model fields require a '
                    f'type annotation; if `{var_name}` is not meant to be a field, you may be able to resolve this '
                    f"error by annotating it as a `ClassVar` or updating `model_config['ignored_types']`.",
                    code='model-field-missing-annotation',
                )

    for ann_name, ann_type in raw_annotations.items():
        if (
            is_valid_privateattr_name(ann_name)
            and ann_name not in private_attributes
            and ann_name not in ignored_names
            and not is_classvar(ann_type)
            and ann_type not in all_ignored_types
            and getattr(ann_type, '__module__', None) != 'functools'
        ):
            if is_annotated(ann_type):
                _, *metadata = typing_extensions.get_args(ann_type)
                private_attr = next((v for v in metadata if isinstance(v, ModelPrivateAttr)), None)
                if private_attr is not None:
                    private_attributes[ann_name] = private_attr
                    continue
            private_attributes[ann_name] = PrivateAttr()

    return private_attributes


def set_default_hash_func(cls: type[BaseModel], bases: tuple[type[Any], ...]) -> None:
    base_hash_func = get_attribute_from_bases(bases, '__hash__')
    new_hash_func = make_hash_func(cls)
    if base_hash_func in {None, object.__hash__} or getattr(base_hash_func, '__code__', None) == new_hash_func.__code__:
        # If `__hash__` is some default, we generate a hash function.
        # It will be `None` if not overridden from BaseModel.
        # It may be `object.__hash__` if there is another
        # parent class earlier in the bases which doesn't override `__hash__` (e.g. `typing.Generic`).
        # It may be a value set by `set_default_hash_func` if `cls` is a subclass of another frozen model.
        # In the last case we still need a new hash function to account for new `model_fields`.
        cls.__hash__ = new_hash_func


def make_hash_func(cls: type[BaseModel]) -> Any:
    getter = operator.itemgetter(*cls.model_fields.keys()) if cls.model_fields else lambda _: 0

    def hash_func(self: Any) -> int:
        try:
            return hash(getter(self.__dict__))
        except KeyError:
            # In rare cases (such as when using the deprecated copy method), the __dict__ may not contain
            # all model fields, which is how we can get here.
            # getter(self.__dict__) is much faster than any 'safe' method that accounts for missing keys,
            # and wrapping it in a `try` doesn't slow things down much in the common case.
            return hash(getter(SafeGetItemProxy(self.__dict__)))

    return hash_func


def set_model_fields(
    cls: type[BaseModel], bases: tuple[type[Any], ...], config_wrapper: ConfigWrapper, types_namespace: dict[str, Any]
) -> None:
    """Collect and set `cls.model_fields` and `cls.__class_vars__`.

    Args:
        cls: BaseModel or dataclass.
        bases: Parents of the class, generally `cls.__bases__`.
        config_wrapper: The config wrapper instance.
        types_namespace: Optional extra namespace to look for types in.
    """
    typevars_map = get_model_typevars_map(cls)
    fields, class_vars = collect_model_fields(cls, bases, config_wrapper, types_namespace, typevars_map=typevars_map)

    cls.model_fields = fields
    cls.__class_vars__.update(class_vars)

    for k in class_vars:
        # Class vars should not be private attributes
        #     We remove them _here_ and not earlier because we rely on inspecting the class to determine its classvars,
        #     but private attributes are determined by inspecting the namespace _prior_ to class creation.
        #     In the case that a classvar with a leading-'_' is defined via a ForwardRef (e.g., when using
        #     `__future__.annotations`), we want to remove the private attribute which was detected _before_ we knew it
        #     evaluated to a classvar

        value = cls.__private_attributes__.pop(k, None)
        if value is not None and value.default is not PydanticUndefined:
            setattr(cls, k, value.default)


def complete_model_class(
    cls: type[BaseModel],
    cls_name: str,
    config_wrapper: ConfigWrapper,
    *,
    raise_errors: bool = True,
    types_namespace: dict[str, Any] | None,
    create_model_module: str | None = None,
) -> bool:
    """Finish building a model class.

    This logic must be called after class has been created since validation functions must be bound
    and `get_type_hints` requires a class object.

    Args:
        cls: BaseModel or dataclass.
        cls_name: The model or dataclass name.
        config_wrapper: The config wrapper instance.
        raise_errors: Whether to raise errors.
        types_namespace: Optional extra namespace to look for types in.
        create_model_module: The module of the class to be created, if created by `create_model`.

    Returns:
        `True` if the model is successfully completed, else `False`.

    Raises:
        PydanticUndefinedAnnotation: If `PydanticUndefinedAnnotation` occurs in`__get_pydantic_core_schema__`
            and `raise_errors=True`.
    """
    typevars_map = get_model_typevars_map(cls)
    gen_schema = GenerateSchema(
        config_wrapper,
        types_namespace,
        typevars_map,
    )

    handler = CallbackGetCoreSchemaHandler(
        partial(gen_schema.generate_schema, from_dunder_get_core_schema=False),
        gen_schema,
        ref_mode='unpack',
    )

    if config_wrapper.defer_build and 'model' in config_wrapper._defer_build_mode:
        set_model_mocks(cls, cls_name)
        return False

    try:
        schema = cls.__get_pydantic_core_schema__(cls, handler)
    except PydanticUndefinedAnnotation as e:
        if raise_errors:
            raise
        set_model_mocks(cls, cls_name, f'`{e.name}`')
        return False

    core_config = config_wrapper.core_config(cls)

    try:
        schema = gen_schema.clean_schema(schema)
    except gen_schema.CollectedInvalid:
        set_model_mocks(cls, cls_name)
        return False

    # debug(schema)
    cls.__pydantic_core_schema__ = schema

    cls.__pydantic_validator__ = create_schema_validator(
        schema,
        cls,
        create_model_module or cls.__module__,
        cls.__qualname__,
        'create_model' if create_model_module else 'BaseModel',
        core_config,
        config_wrapper.plugin_settings,
    )
    cls.__pydantic_serializer__ = SchemaSerializer(schema, core_config)
    cls.__pydantic_complete__ = True

    # set __signature__ attr only for model class, but not for its instances
    cls.__signature__ = ClassAttribute(
        '__signature__',
        generate_pydantic_signature(init=cls.__init__, fields=cls.model_fields, config_wrapper=config_wrapper),
    )
    return True


def set_deprecated_descriptors(cls: type[BaseModel]) -> None:
    """Set data descriptors on the class for deprecated fields."""
    for field, field_info in cls.model_fields.items():
        if (msg := field_info.deprecation_message) is not None:
            desc = _DeprecatedFieldDescriptor(msg)
            desc.__set_name__(cls, field)
            setattr(cls, field, desc)

    for field, computed_field_info in cls.model_computed_fields.items():
        if (
            (msg := computed_field_info.deprecation_message) is not None
            # Avoid having two warnings emitted:
            and not hasattr(unwrap_wrapped_function(computed_field_info.wrapped_property), '__deprecated__')
        ):
            desc = _DeprecatedFieldDescriptor(msg, computed_field_info.wrapped_property)
            desc.__set_name__(cls, field)
            setattr(cls, field, desc)


class _DeprecatedFieldDescriptor:
    """Data descriptor used to emit a runtime deprecation warning before accessing a deprecated field.

    Attributes:
        msg: The deprecation message to be emitted.
        wrapped_property: The property instance if the deprecated field is a computed field, or `None`.
        field_name: The name of the field being deprecated.
    """

    field_name: str

    def __init__(self, msg: str, wrapped_property: property | None = None) -> None:
        self.msg = msg
        self.wrapped_property = wrapped_property

    def __set_name__(self, cls: type[BaseModel], name: str) -> None:
        self.field_name = name

    def __get__(self, obj: BaseModel | None, obj_type: type[BaseModel] | None = None) -> Any:
        if obj is None:
            raise AttributeError(self.field_name)

        warnings.warn(self.msg, builtins.DeprecationWarning, stacklevel=2)

        if self.wrapped_property is not None:
            return self.wrapped_property.__get__(obj, obj_type)
        return obj.__dict__[self.field_name]

    # Defined to take precedence over the instance's dictionary
    # Note that it will not be called when setting a value on a model instance
    # as `BaseModel.__setattr__` is defined and takes priority.
    def __set__(self, obj: Any, value: Any) -> NoReturn:
        raise AttributeError(self.field_name)


class _PydanticWeakRef:
    """Wrapper for `weakref.ref` that enables `pickle` serialization.

    Cloudpickle fails to serialize `weakref.ref` objects due to an arcane error related
    to abstract base classes (`abc.ABC`). This class works around the issue by wrapping
    `weakref.ref` instead of subclassing it.

    See https://github.com/pydantic/pydantic/issues/6763 for context.

    Semantics:
        - If not pickled, behaves the same as a `weakref.ref`.
        - If pickled along with the referenced object, the same `weakref.ref` behavior
          will be maintained between them after unpickling.
        - If pickled without the referenced object, after unpickling the underlying
          reference will be cleared (`__call__` will always return `None`).
    """

    def __init__(self, obj: Any):
        if obj is None:
            # The object will be `None` upon deserialization if the serialized weakref
            # had lost its underlying object.
            self._wr = None
        else:
            self._wr = weakref.ref(obj)

    def __call__(self) -> Any:
        if self._wr is None:
            return None
        else:
            return self._wr()

    def __reduce__(self) -> tuple[Callable, tuple[weakref.ReferenceType | None]]:
        return _PydanticWeakRef, (self(),)


def build_lenient_weakvaluedict(d: dict[str, Any] | None) -> dict[str, Any] | None:
    """Takes an input dictionary, and produces a new value that (invertibly) replaces the values with weakrefs.

    We can't just use a WeakValueDictionary because many types (including int, str, etc.) can't be stored as values
    in a WeakValueDictionary.

    The `unpack_lenient_weakvaluedict` function can be used to reverse this operation.
    """
    if d is None:
        return None
    result = {}
    for k, v in d.items():
        try:
            proxy = _PydanticWeakRef(v)
        except TypeError:
            proxy = v
        result[k] = proxy
    return result


def unpack_lenient_weakvaluedict(d: dict[str, Any] | None) -> dict[str, Any] | None:
    """Inverts the transform performed by `build_lenient_weakvaluedict`."""
    if d is None:
        return None

    result = {}
    for k, v in d.items():
        if isinstance(v, _PydanticWeakRef):
            v = v()
            if v is not None:
                result[k] = v
        else:
            result[k] = v
    return result


def default_ignored_types() -> tuple[type[Any], ...]:
    from ..fields import ComputedFieldInfo

    return (
        FunctionType,
        property,
        classmethod,
        staticmethod,
        PydanticDescriptorProxy,
        ComputedFieldInfo,
        ValidateCallWrapper,
    )