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dataclasses.py
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""" The main purpose is to enhance stdlib dataclasses by adding validation A pydantic dataclass can be generated from scratch or from a stdlib one. Behind the scene, a pydantic dataclass is just like a regular one on which we attach a `BaseModel` and magic methods to trigger the validation of the data. `__init__` and `__post_init__` are hence overridden and have extra logic to be able to validate input data. When a pydantic dataclass is generated from scratch, it's just a plain dataclass with validation triggered at initialization The tricky part if for stdlib dataclasses that are converted after into pydantic ones e.g. ```py @dataclasses.dataclass class M: x: int ValidatedM = pydantic.dataclasses.dataclass(M) ``` We indeed still want to support equality, hashing, repr, ... as if it was the stdlib one! ```py assert isinstance(ValidatedM(x=1), M) assert ValidatedM(x=1) == M(x=1) ``` This means we **don't want to create a new dataclass that inherits from it** The trick is to create a wrapper around `M` that will act as a proxy to trigger validation without altering default `M` behaviour. """ import copy import dataclasses import sys from contextlib import contextmanager from functools import wraps try: from functools import cached_property except ImportError: # cached_property available only for python3.8+ pass from typing import TYPE_CHECKING, Any, Callable, ClassVar, Dict, Generator, Optional, Type, TypeVar, Union, overload from typing_extensions import dataclass_transform from pydantic.v1.class_validators import gather_all_validators from pydantic.v1.config import BaseConfig, ConfigDict, Extra, get_config from pydantic.v1.error_wrappers import ValidationError from pydantic.v1.errors import DataclassTypeError from pydantic.v1.fields import Field, FieldInfo, Required, Undefined from pydantic.v1.main import create_model, validate_model from pydantic.v1.utils import ClassAttribute if TYPE_CHECKING: from pydantic.v1.main import BaseModel from pydantic.v1.typing import CallableGenerator, NoArgAnyCallable DataclassT = TypeVar('DataclassT', bound='Dataclass') DataclassClassOrWrapper = Union[Type['Dataclass'], 'DataclassProxy'] class Dataclass: # stdlib attributes __dataclass_fields__: ClassVar[Dict[str, Any]] __dataclass_params__: ClassVar[Any] # in reality `dataclasses._DataclassParams` __post_init__: ClassVar[Callable[..., None]] # Added by pydantic __pydantic_run_validation__: ClassVar[bool] __post_init_post_parse__: ClassVar[Callable[..., None]] __pydantic_initialised__: ClassVar[bool] __pydantic_model__: ClassVar[Type[BaseModel]] __pydantic_validate_values__: ClassVar[Callable[['Dataclass'], None]] __pydantic_has_field_info_default__: ClassVar[bool] # whether a `pydantic.Field` is used as default value def __init__(self, *args: object, **kwargs: object) -> None: pass @classmethod def __get_validators__(cls: Type['Dataclass']) -> 'CallableGenerator': pass @classmethod def __validate__(cls: Type['DataclassT'], v: Any) -> 'DataclassT': pass __all__ = [ 'dataclass', 'set_validation', 'create_pydantic_model_from_dataclass', 'is_builtin_dataclass', 'make_dataclass_validator', ] _T = TypeVar('_T') if sys.version_info >= (3, 10): @dataclass_transform(field_specifiers=(dataclasses.field, Field)) @overload def dataclass( *, init: bool = True, repr: bool = True, eq: bool = True, order: bool = False, unsafe_hash: bool = False, frozen: bool = False, config: Union[ConfigDict, Type[object], None] = None, validate_on_init: Optional[bool] = None, use_proxy: Optional[bool] = None, kw_only: bool = ..., ) -> Callable[[Type[_T]], 'DataclassClassOrWrapper']: ... @dataclass_transform(field_specifiers=(dataclasses.field, Field)) @overload def dataclass( _cls: Type[_T], *, init: bool = True, repr: bool = True, eq: bool = True, order: bool = False, unsafe_hash: bool = False, frozen: bool = False, config: Union[ConfigDict, Type[object], None] = None, validate_on_init: Optional[bool] = None, use_proxy: Optional[bool] = None, kw_only: bool = ..., ) -> 'DataclassClassOrWrapper': ... else: @dataclass_transform(field_specifiers=(dataclasses.field, Field)) @overload def dataclass( *, init: bool = True, repr: bool = True, eq: bool = True, order: bool = False, unsafe_hash: bool = False, frozen: bool = False, config: Union[ConfigDict, Type[object], None] = None, validate_on_init: Optional[bool] = None, use_proxy: Optional[bool] = None, ) -> Callable[[Type[_T]], 'DataclassClassOrWrapper']: ... @dataclass_transform(field_specifiers=(dataclasses.field, Field)) @overload def dataclass( _cls: Type[_T], *, init: bool = True, repr: bool = True, eq: bool = True, order: bool = False, unsafe_hash: bool = False, frozen: bool = False, config: Union[ConfigDict, Type[object], None] = None, validate_on_init: Optional[bool] = None, use_proxy: Optional[bool] = None, ) -> 'DataclassClassOrWrapper': ... @dataclass_transform(field_specifiers=(dataclasses.field, Field)) def dataclass( _cls: Optional[Type[_T]] = None, *, init: bool = True, repr: bool = True, eq: bool = True, order: bool = False, unsafe_hash: bool = False, frozen: bool = False, config: Union[ConfigDict, Type[object], None] = None, validate_on_init: Optional[bool] = None, use_proxy: Optional[bool] = None, kw_only: bool = False, ) -> Union[Callable[[Type[_T]], 'DataclassClassOrWrapper'], 'DataclassClassOrWrapper']: """ Like the python standard lib dataclasses but with type validation. The result is either a pydantic dataclass that will validate input data or a wrapper that will trigger validation around a stdlib dataclass to avoid modifying it directly """ the_config = get_config(config) def wrap(cls: Type[Any]) -> 'DataclassClassOrWrapper': should_use_proxy = ( use_proxy if use_proxy is not None else ( is_builtin_dataclass(cls) and (cls.__bases__[0] is object or set(dir(cls)) == set(dir(cls.__bases__[0]))) ) ) if should_use_proxy: dc_cls_doc = '' dc_cls = DataclassProxy(cls) default_validate_on_init = False else: dc_cls_doc = cls.__doc__ or '' # needs to be done before generating dataclass if sys.version_info >= (3, 10): dc_cls = dataclasses.dataclass( cls, init=init, repr=repr, eq=eq, order=order, unsafe_hash=unsafe_hash, frozen=frozen, kw_only=kw_only, ) else: dc_cls = dataclasses.dataclass( # type: ignore cls, init=init, repr=repr, eq=eq, order=order, unsafe_hash=unsafe_hash, frozen=frozen ) default_validate_on_init = True should_validate_on_init = default_validate_on_init if validate_on_init is None else validate_on_init _add_pydantic_validation_attributes(cls, the_config, should_validate_on_init, dc_cls_doc) dc_cls.__pydantic_model__.__try_update_forward_refs__(**{cls.__name__: cls}) return dc_cls if _cls is None: return wrap return wrap(_cls) @contextmanager def set_validation(cls: Type['DataclassT'], value: bool) -> Generator[Type['DataclassT'], None, None]: original_run_validation = cls.__pydantic_run_validation__ try: cls.__pydantic_run_validation__ = value yield cls finally: cls.__pydantic_run_validation__ = original_run_validation class DataclassProxy: __slots__ = '__dataclass__' def __init__(self, dc_cls: Type['Dataclass']) -> None: object.__setattr__(self, '__dataclass__', dc_cls) def __call__(self, *args: Any, **kwargs: Any) -> Any: with set_validation(self.__dataclass__, True): return self.__dataclass__(*args, **kwargs) def __getattr__(self, name: str) -> Any: return getattr(self.__dataclass__, name) def __setattr__(self, __name: str, __value: Any) -> None: return setattr(self.__dataclass__, __name, __value) def __instancecheck__(self, instance: Any) -> bool: return isinstance(instance, self.__dataclass__) def __copy__(self) -> 'DataclassProxy': return DataclassProxy(copy.copy(self.__dataclass__)) def __deepcopy__(self, memo: Any) -> 'DataclassProxy': return DataclassProxy(copy.deepcopy(self.__dataclass__, memo)) def _add_pydantic_validation_attributes( # noqa: C901 (ignore complexity) dc_cls: Type['Dataclass'], config: Type[BaseConfig], validate_on_init: bool, dc_cls_doc: str, ) -> None: """ We need to replace the right method. If no `__post_init__` has been set in the stdlib dataclass it won't even exist (code is generated on the fly by `dataclasses`) By default, we run validation after `__init__` or `__post_init__` if defined """ init = dc_cls.__init__ @wraps(init) def handle_extra_init(self: 'Dataclass', *args: Any, **kwargs: Any) -> None: if config.extra == Extra.ignore: init(self, *args, **{k: v for k, v in kwargs.items() if k in self.__dataclass_fields__}) elif config.extra == Extra.allow: for k, v in kwargs.items(): self.__dict__.setdefault(k, v) init(self, *args, **{k: v for k, v in kwargs.items() if k in self.__dataclass_fields__}) else: init(self, *args, **kwargs) if hasattr(dc_cls, '__post_init__'): try: post_init = dc_cls.__post_init__.__wrapped__ # type: ignore[attr-defined] except AttributeError: post_init = dc_cls.__post_init__ @wraps(post_init) def new_post_init(self: 'Dataclass', *args: Any, **kwargs: Any) -> None: if config.post_init_call == 'before_validation': post_init(self, *args, **kwargs) if self.__class__.__pydantic_run_validation__: self.__pydantic_validate_values__() if hasattr(self, '__post_init_post_parse__'): self.__post_init_post_parse__(*args, **kwargs) if config.post_init_call == 'after_validation': post_init(self, *args, **kwargs) setattr(dc_cls, '__init__', handle_extra_init) setattr(dc_cls, '__post_init__', new_post_init) else: @wraps(init) def new_init(self: 'Dataclass', *args: Any, **kwargs: Any) -> None: handle_extra_init(self, *args, **kwargs) if self.__class__.__pydantic_run_validation__: self.__pydantic_validate_values__() if hasattr(self, '__post_init_post_parse__'): # We need to find again the initvars. To do that we use `__dataclass_fields__` instead of # public method `dataclasses.fields` # get all initvars and their default values initvars_and_values: Dict[str, Any] = {} for i, f in enumerate(self.__class__.__dataclass_fields__.values()): if f._field_type is dataclasses._FIELD_INITVAR: # type: ignore[attr-defined] try: # set arg value by default initvars_and_values[f.name] = args[i] except IndexError: initvars_and_values[f.name] = kwargs.get(f.name, f.default) self.__post_init_post_parse__(**initvars_and_values) setattr(dc_cls, '__init__', new_init) setattr(dc_cls, '__pydantic_run_validation__', ClassAttribute('__pydantic_run_validation__', validate_on_init)) setattr(dc_cls, '__pydantic_initialised__', False) setattr(dc_cls, '__pydantic_model__', create_pydantic_model_from_dataclass(dc_cls, config, dc_cls_doc)) setattr(dc_cls, '__pydantic_validate_values__', _dataclass_validate_values) setattr(dc_cls, '__validate__', classmethod(_validate_dataclass)) setattr(dc_cls, '__get_validators__', classmethod(_get_validators)) if dc_cls.__pydantic_model__.__config__.validate_assignment and not dc_cls.__dataclass_params__.frozen: setattr(dc_cls, '__setattr__', _dataclass_validate_assignment_setattr) def _get_validators(cls: 'DataclassClassOrWrapper') -> 'CallableGenerator': yield cls.__validate__ def _validate_dataclass(cls: Type['DataclassT'], v: Any) -> 'DataclassT': with set_validation(cls, True): if isinstance(v, cls): v.__pydantic_validate_values__() return v elif isinstance(v, (list, tuple)): return cls(*v) elif isinstance(v, dict): return cls(**v) else: raise DataclassTypeError(class_name=cls.__name__) def create_pydantic_model_from_dataclass( dc_cls: Type['Dataclass'], config: Type[Any] = BaseConfig, dc_cls_doc: Optional[str] = None, ) -> Type['BaseModel']: field_definitions: Dict[str, Any] = {} for field in dataclasses.fields(dc_cls): default: Any = Undefined default_factory: Optional['NoArgAnyCallable'] = None field_info: FieldInfo if field.default is not dataclasses.MISSING: default = field.default elif field.default_factory is not dataclasses.MISSING: default_factory = field.default_factory else: default = Required if isinstance(default, FieldInfo): field_info = default dc_cls.__pydantic_has_field_info_default__ = True else: field_info = Field(default=default, default_factory=default_factory, **field.metadata) field_definitions[field.name] = (field.type, field_info) validators = gather_all_validators(dc_cls) model: Type['BaseModel'] = create_model( dc_cls.__name__, __config__=config, __module__=dc_cls.__module__, __validators__=validators, __cls_kwargs__={'__resolve_forward_refs__': False}, **field_definitions, ) model.__doc__ = dc_cls_doc if dc_cls_doc is not None else dc_cls.__doc__ or '' return model if sys.version_info >= (3, 8): def _is_field_cached_property(obj: 'Dataclass', k: str) -> bool: return isinstance(getattr(type(obj), k, None), cached_property) else: def _is_field_cached_property(obj: 'Dataclass', k: str) -> bool: return False def _dataclass_validate_values(self: 'Dataclass') -> None: # validation errors can occur if this function is called twice on an already initialised dataclass. # for example if Extra.forbid is enabled, it would consider __pydantic_initialised__ an invalid extra property if getattr(self, '__pydantic_initialised__'): return if getattr(self, '__pydantic_has_field_info_default__', False): # We need to remove `FieldInfo` values since they are not valid as input # It's ok to do that because they are obviously the default values! input_data = { k: v for k, v in self.__dict__.items() if not (isinstance(v, FieldInfo) or _is_field_cached_property(self, k)) } else: input_data = {k: v for k, v in self.__dict__.items() if not _is_field_cached_property(self, k)} d, _, validation_error = validate_model(self.__pydantic_model__, input_data, cls=self.__class__) if validation_error: raise validation_error self.__dict__.update(d) object.__setattr__(self, '__pydantic_initialised__', True) def _dataclass_validate_assignment_setattr(self: 'Dataclass', name: str, value: Any) -> None: if self.__pydantic_initialised__: d = dict(self.__dict__) d.pop(name, None) known_field = self.__pydantic_model__.__fields__.get(name, None) if known_field: value, error_ = known_field.validate(value, d, loc=name, cls=self.__class__) if error_: raise ValidationError([error_], self.__class__) object.__setattr__(self, name, value) def is_builtin_dataclass(_cls: Type[Any]) -> bool: """ Whether a class is a stdlib dataclass (useful to discriminated a pydantic dataclass that is actually a wrapper around a stdlib dataclass) we check that - `_cls` is a dataclass - `_cls` is not a processed pydantic dataclass (with a basemodel attached) - `_cls` is not a pydantic dataclass inheriting directly from a stdlib dataclass e.g. ``` @dataclasses.dataclass class A: x: int @pydantic.dataclasses.dataclass class B(A): y: int ``` In this case, when we first check `B`, we make an extra check and look at the annotations ('y'), which won't be a superset of all the dataclass fields (only the stdlib fields i.e. 'x') """ return ( dataclasses.is_dataclass(_cls) and not hasattr(_cls, '__pydantic_model__') and set(_cls.__dataclass_fields__).issuperset(set(getattr(_cls, '__annotations__', {}))) ) def make_dataclass_validator(dc_cls: Type['Dataclass'], config: Type[BaseConfig]) -> 'CallableGenerator': """ Create a pydantic.dataclass from a builtin dataclass to add type validation and yield the validators It retrieves the parameters of the dataclass and forwards them to the newly created dataclass """ yield from _get_validators(dataclass(dc_cls, config=config, use_proxy=True))