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401 lines
17 KiB
401 lines
17 KiB
import sys
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import types
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import typing
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from typing import (
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TYPE_CHECKING,
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Any,
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ClassVar,
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Dict,
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ForwardRef,
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Generic,
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Iterator,
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List,
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Mapping,
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Optional,
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Tuple,
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Type,
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TypeVar,
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Union,
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cast,
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)
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from weakref import WeakKeyDictionary, WeakValueDictionary
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from typing_extensions import Annotated, Literal as ExtLiteral
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from .class_validators import gather_all_validators
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from .fields import DeferredType
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from .main import BaseModel, create_model
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from .types import JsonWrapper
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from .typing import display_as_type, get_all_type_hints, get_args, get_origin, typing_base
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from .utils import all_identical, lenient_issubclass
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if sys.version_info >= (3, 10):
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from typing import _UnionGenericAlias
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if sys.version_info >= (3, 8):
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from typing import Literal
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GenericModelT = TypeVar('GenericModelT', bound='GenericModel')
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TypeVarType = Any # since mypy doesn't allow the use of TypeVar as a type
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CacheKey = Tuple[Type[Any], Any, Tuple[Any, ...]]
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Parametrization = Mapping[TypeVarType, Type[Any]]
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# weak dictionaries allow the dynamically created parametrized versions of generic models to get collected
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# once they are no longer referenced by the caller.
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if sys.version_info >= (3, 9): # Typing for weak dictionaries available at 3.9
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GenericTypesCache = WeakValueDictionary[CacheKey, Type[BaseModel]]
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AssignedParameters = WeakKeyDictionary[Type[BaseModel], Parametrization]
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else:
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GenericTypesCache = WeakValueDictionary
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AssignedParameters = WeakKeyDictionary
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# _generic_types_cache is a Mapping from __class_getitem__ arguments to the parametrized version of generic models.
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# This ensures multiple calls of e.g. A[B] return always the same class.
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_generic_types_cache = GenericTypesCache()
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# _assigned_parameters is a Mapping from parametrized version of generic models to assigned types of parametrizations
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# as captured during construction of the class (not instances).
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# E.g., for generic model `Model[A, B]`, when parametrized model `Model[int, str]` is created,
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# `Model[int, str]`: {A: int, B: str}` will be stored in `_assigned_parameters`.
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# (This information is only otherwise available after creation from the class name string).
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_assigned_parameters = AssignedParameters()
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class GenericModel(BaseModel):
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__slots__ = ()
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__concrete__: ClassVar[bool] = False
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if TYPE_CHECKING:
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# Putting this in a TYPE_CHECKING block allows us to replace `if Generic not in cls.__bases__` with
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# `not hasattr(cls, "__parameters__")`. This means we don't need to force non-concrete subclasses of
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# `GenericModel` to also inherit from `Generic`, which would require changes to the use of `create_model` below.
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__parameters__: ClassVar[Tuple[TypeVarType, ...]]
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# Setting the return type as Type[Any] instead of Type[BaseModel] prevents PyCharm warnings
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def __class_getitem__(cls: Type[GenericModelT], params: Union[Type[Any], Tuple[Type[Any], ...]]) -> Type[Any]:
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"""Instantiates a new class from a generic class `cls` and type variables `params`.
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:param params: Tuple of types the class . Given a generic class
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`Model` with 2 type variables and a concrete model `Model[str, int]`,
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the value `(str, int)` would be passed to `params`.
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:return: New model class inheriting from `cls` with instantiated
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types described by `params`. If no parameters are given, `cls` is
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returned as is.
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"""
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def _cache_key(_params: Any) -> CacheKey:
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args = get_args(_params)
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# python returns a list for Callables, which is not hashable
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if len(args) == 2 and isinstance(args[0], list):
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args = (tuple(args[0]), args[1])
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return cls, _params, args
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cached = _generic_types_cache.get(_cache_key(params))
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if cached is not None:
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return cached
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if cls.__concrete__ and Generic not in cls.__bases__:
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raise TypeError('Cannot parameterize a concrete instantiation of a generic model')
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if not isinstance(params, tuple):
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params = (params,)
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if cls is GenericModel and any(isinstance(param, TypeVar) for param in params):
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raise TypeError('Type parameters should be placed on typing.Generic, not GenericModel')
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if not hasattr(cls, '__parameters__'):
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raise TypeError(f'Type {cls.__name__} must inherit from typing.Generic before being parameterized')
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check_parameters_count(cls, params)
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# Build map from generic typevars to passed params
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typevars_map: Dict[TypeVarType, Type[Any]] = dict(zip(cls.__parameters__, params))
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if all_identical(typevars_map.keys(), typevars_map.values()) and typevars_map:
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return cls # if arguments are equal to parameters it's the same object
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# Create new model with original model as parent inserting fields with DeferredType.
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model_name = cls.__concrete_name__(params)
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validators = gather_all_validators(cls)
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type_hints = get_all_type_hints(cls).items()
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instance_type_hints = {k: v for k, v in type_hints if get_origin(v) is not ClassVar}
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fields = {k: (DeferredType(), cls.__fields__[k].field_info) for k in instance_type_hints if k in cls.__fields__}
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model_module, called_globally = get_caller_frame_info()
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created_model = cast(
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Type[GenericModel], # casting ensures mypy is aware of the __concrete__ and __parameters__ attributes
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create_model(
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model_name,
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__module__=model_module or cls.__module__,
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__base__=(cls,) + tuple(cls.__parameterized_bases__(typevars_map)),
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__config__=None,
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__validators__=validators,
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__cls_kwargs__=None,
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**fields,
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),
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)
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_assigned_parameters[created_model] = typevars_map
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if called_globally: # create global reference and therefore allow pickling
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object_by_reference = None
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reference_name = model_name
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reference_module_globals = sys.modules[created_model.__module__].__dict__
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while object_by_reference is not created_model:
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object_by_reference = reference_module_globals.setdefault(reference_name, created_model)
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reference_name += '_'
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created_model.Config = cls.Config
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# Find any typevars that are still present in the model.
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# If none are left, the model is fully "concrete", otherwise the new
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# class is a generic class as well taking the found typevars as
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# parameters.
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new_params = tuple(
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{param: None for param in iter_contained_typevars(typevars_map.values())}
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) # use dict as ordered set
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created_model.__concrete__ = not new_params
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if new_params:
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created_model.__parameters__ = new_params
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# Save created model in cache so we don't end up creating duplicate
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# models that should be identical.
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_generic_types_cache[_cache_key(params)] = created_model
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if len(params) == 1:
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_generic_types_cache[_cache_key(params[0])] = created_model
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# Recursively walk class type hints and replace generic typevars
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# with concrete types that were passed.
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_prepare_model_fields(created_model, fields, instance_type_hints, typevars_map)
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return created_model
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@classmethod
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def __concrete_name__(cls: Type[Any], params: Tuple[Type[Any], ...]) -> str:
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"""Compute class name for child classes.
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:param params: Tuple of types the class . Given a generic class
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`Model` with 2 type variables and a concrete model `Model[str, int]`,
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the value `(str, int)` would be passed to `params`.
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:return: String representing a the new class where `params` are
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passed to `cls` as type variables.
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This method can be overridden to achieve a custom naming scheme for GenericModels.
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"""
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param_names = [display_as_type(param) for param in params]
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params_component = ', '.join(param_names)
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return f'{cls.__name__}[{params_component}]'
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@classmethod
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def __parameterized_bases__(cls, typevars_map: Parametrization) -> Iterator[Type[Any]]:
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"""
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Returns unbound bases of cls parameterised to given type variables
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:param typevars_map: Dictionary of type applications for binding subclasses.
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Given a generic class `Model` with 2 type variables [S, T]
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and a concrete model `Model[str, int]`,
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the value `{S: str, T: int}` would be passed to `typevars_map`.
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:return: an iterator of generic sub classes, parameterised by `typevars_map`
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and other assigned parameters of `cls`
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e.g.:
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```
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class A(GenericModel, Generic[T]):
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...
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class B(A[V], Generic[V]):
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...
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assert A[int] in B.__parameterized_bases__({V: int})
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```
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"""
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def build_base_model(
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base_model: Type[GenericModel], mapped_types: Parametrization
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) -> Iterator[Type[GenericModel]]:
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base_parameters = tuple(mapped_types[param] for param in base_model.__parameters__)
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parameterized_base = base_model.__class_getitem__(base_parameters)
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if parameterized_base is base_model or parameterized_base is cls:
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# Avoid duplication in MRO
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return
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yield parameterized_base
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for base_model in cls.__bases__:
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if not issubclass(base_model, GenericModel):
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# not a class that can be meaningfully parameterized
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continue
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elif not getattr(base_model, '__parameters__', None):
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# base_model is "GenericModel" (and has no __parameters__)
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# or
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# base_model is already concrete, and will be included transitively via cls.
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continue
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elif cls in _assigned_parameters:
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if base_model in _assigned_parameters:
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# cls is partially parameterised but not from base_model
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# e.g. cls = B[S], base_model = A[S]
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# B[S][int] should subclass A[int], (and will be transitively via B[int])
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# but it's not viable to consistently subclass types with arbitrary construction
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# So don't attempt to include A[S][int]
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continue
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else: # base_model not in _assigned_parameters:
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# cls is partially parameterized, base_model is original generic
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# e.g. cls = B[str, T], base_model = B[S, T]
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# Need to determine the mapping for the base_model parameters
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mapped_types: Parametrization = {
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key: typevars_map.get(value, value) for key, value in _assigned_parameters[cls].items()
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}
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yield from build_base_model(base_model, mapped_types)
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else:
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# cls is base generic, so base_class has a distinct base
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# can construct the Parameterised base model using typevars_map directly
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yield from build_base_model(base_model, typevars_map)
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def replace_types(type_: Any, type_map: Mapping[Any, Any]) -> Any:
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"""Return type with all occurrences of `type_map` keys recursively replaced with their values.
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:param type_: Any type, class or generic alias
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:param type_map: Mapping from `TypeVar` instance to concrete types.
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:return: New type representing the basic structure of `type_` with all
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`typevar_map` keys recursively replaced.
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>>> replace_types(Tuple[str, Union[List[str], float]], {str: int})
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Tuple[int, Union[List[int], float]]
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"""
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if not type_map:
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return type_
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type_args = get_args(type_)
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origin_type = get_origin(type_)
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if origin_type is Annotated:
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annotated_type, *annotations = type_args
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return Annotated[replace_types(annotated_type, type_map), tuple(annotations)]
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if (origin_type is ExtLiteral) or (sys.version_info >= (3, 8) and origin_type is Literal):
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return type_map.get(type_, type_)
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# Having type args is a good indicator that this is a typing module
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# class instantiation or a generic alias of some sort.
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if type_args:
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resolved_type_args = tuple(replace_types(arg, type_map) for arg in type_args)
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if all_identical(type_args, resolved_type_args):
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# If all arguments are the same, there is no need to modify the
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# type or create a new object at all
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return type_
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if (
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origin_type is not None
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and isinstance(type_, typing_base)
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and not isinstance(origin_type, typing_base)
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and getattr(type_, '_name', None) is not None
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):
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# In python < 3.9 generic aliases don't exist so any of these like `list`,
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# `type` or `collections.abc.Callable` need to be translated.
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# See: https://www.python.org/dev/peps/pep-0585
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origin_type = getattr(typing, type_._name)
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assert origin_type is not None
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# PEP-604 syntax (Ex.: list | str) is represented with a types.UnionType object that does not have __getitem__.
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# We also cannot use isinstance() since we have to compare types.
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if sys.version_info >= (3, 10) and origin_type is types.UnionType: # noqa: E721
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return _UnionGenericAlias(origin_type, resolved_type_args)
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return origin_type[resolved_type_args]
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# We handle pydantic generic models separately as they don't have the same
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# semantics as "typing" classes or generic aliases
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if not origin_type and lenient_issubclass(type_, GenericModel) and not type_.__concrete__:
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type_args = type_.__parameters__
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resolved_type_args = tuple(replace_types(t, type_map) for t in type_args)
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if all_identical(type_args, resolved_type_args):
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return type_
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return type_[resolved_type_args]
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# Handle special case for typehints that can have lists as arguments.
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# `typing.Callable[[int, str], int]` is an example for this.
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if isinstance(type_, (List, list)):
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resolved_list = list(replace_types(element, type_map) for element in type_)
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if all_identical(type_, resolved_list):
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return type_
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return resolved_list
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# For JsonWrapperValue, need to handle its inner type to allow correct parsing
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# of generic Json arguments like Json[T]
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if not origin_type and lenient_issubclass(type_, JsonWrapper):
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type_.inner_type = replace_types(type_.inner_type, type_map)
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return type_
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# If all else fails, we try to resolve the type directly and otherwise just
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# return the input with no modifications.
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new_type = type_map.get(type_, type_)
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# Convert string to ForwardRef
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if isinstance(new_type, str):
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return ForwardRef(new_type)
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else:
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return new_type
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def check_parameters_count(cls: Type[GenericModel], parameters: Tuple[Any, ...]) -> None:
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actual = len(parameters)
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expected = len(cls.__parameters__)
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if actual != expected:
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description = 'many' if actual > expected else 'few'
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raise TypeError(f'Too {description} parameters for {cls.__name__}; actual {actual}, expected {expected}')
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DictValues: Type[Any] = {}.values().__class__
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def iter_contained_typevars(v: Any) -> Iterator[TypeVarType]:
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"""Recursively iterate through all subtypes and type args of `v` and yield any typevars that are found."""
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if isinstance(v, TypeVar):
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yield v
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elif hasattr(v, '__parameters__') and not get_origin(v) and lenient_issubclass(v, GenericModel):
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yield from v.__parameters__
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elif isinstance(v, (DictValues, list)):
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for var in v:
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yield from iter_contained_typevars(var)
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else:
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args = get_args(v)
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for arg in args:
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yield from iter_contained_typevars(arg)
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def get_caller_frame_info() -> Tuple[Optional[str], bool]:
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"""
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Used inside a function to check whether it was called globally
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Will only work against non-compiled code, therefore used only in pydantic.generics
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:returns Tuple[module_name, called_globally]
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"""
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try:
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previous_caller_frame = sys._getframe(2)
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except ValueError as e:
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raise RuntimeError('This function must be used inside another function') from e
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except AttributeError: # sys module does not have _getframe function, so there's nothing we can do about it
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return None, False
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frame_globals = previous_caller_frame.f_globals
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return frame_globals.get('__name__'), previous_caller_frame.f_locals is frame_globals
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def _prepare_model_fields(
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created_model: Type[GenericModel],
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fields: Mapping[str, Any],
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instance_type_hints: Mapping[str, type],
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typevars_map: Mapping[Any, type],
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) -> None:
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"""
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Replace DeferredType fields with concrete type hints and prepare them.
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"""
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for key, field in created_model.__fields__.items():
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if key not in fields:
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assert field.type_.__class__ is not DeferredType
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# https://github.com/nedbat/coveragepy/issues/198
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continue # pragma: no cover
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assert field.type_.__class__ is DeferredType, field.type_.__class__
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field_type_hint = instance_type_hints[key]
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concrete_type = replace_types(field_type_hint, typevars_map)
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field.type_ = concrete_type
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field.outer_type_ = concrete_type
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field.prepare()
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created_model.__annotations__[key] = concrete_type
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